Research Article Separate Determination of Borohydride...
11
Research Article Separate Determination of Borohydride, Borate, Hydroxide, and Carbonate in the Borohydride Fuel Cell by Acid-Base and Iodometric Potentiometric Titration A. V. Churikov, S. L. Shmakov, V. O. Romanova, K. V. Zapsis, A. V. Ushakov, A. V. Ivanishchev, and M. A. Churikov Institute of Chemistry, Saratov State University, 83 Astrakhanskaya Street, Saratov 410012, Russia Correspondence should be addressed to V. O. Romanova; nikanor [email protected] Received 23 May 2013; Accepted 26 November 2013; Published 29 January 2014 Academic Editor: C´ esar Sequeira Copyright © 2014 A. V. Churikov et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A methodology for quantitative chemical analysis of the complex “borohydride-borate-hydroxide-carbonate-water” mixtures used as fuel in the borohydride fuel cell was developed and optimized. e methodology includes the combined usage of the acid-base and iodometric titration methods. e acid-base titration method, which simultaneously uses the technique of differentiation and computer simulation of titration curves, allows one to determine the contents of hydroxide (alkali), carbonate, and total “borate + borohydride” content. e iodometric titration method allows one to selectively determine borohydride, so the content of each of OH − , BH 4 − , BO 2 − , and CO 3 2− anions in the fuel becomes estimated. e average determination error depends on the number and ratio of compounds in a mixture. Specific details of the analysis of various fuel mixtures are discussed. 1. Introduction e intense progress of electric vehicles, portable electronics, mobile communication tools, and other systems, which require independent power supply, stimulates the design of new chemical power sources [1, 2]. ese sources have to possess high-energy specific characteristics but also they must be safe and comfortable in use. In this connection, the development of fuel cells (FC) in which chemical energy is directly converted into electrical one becomes most topical. Especially, direct borohydride fuel cells (DBFCs) are inten- sively evolved in which alkaline aqueous solutions of such salts as LiBH 4 , NaBH 4 , and KBH 4 are used as fuel [3–9]. In these systems, electrical energy is generated by means of hydrolysis and electrochemical oxidation of borohydrides into borates. In alkaline media, these are LiBO 2 , NaBO 2 , and KBO 2 [10–12] whose solubility essentially influences the power characteristics of FC [13–15]. e difficulty of the design of effective and sustainable anode electrocatalysts for the anodic oxidation of borohydride limits the efficiency and power density attainable in these devices [16–18]. e fuel of DBFCs is a multiple mixture whose specific characteristics directly depend on the ratio of its components BH 4 − /OH − /H 2 O[19–24]. It can be an aqueous solution of NaOH and NaBH 4 in the initial state and an aqueous solution of NaOH, NaBH 4 , and NaBO 2 in the discharged (partially or fully) state. Besides, the fuel composition is changed due to side reaction; it can dry up or water out, and it also can be acidified and/or carbonated by chemical interaction with carbon dioxide from air. In this case, additional components will appear in the solution, such as carbonate Na 2 CO 3 and bicarbonate NaHCO 3 at deeper carbonization in accordance with the ionic reactions: I stage (carbonate formation) 2OH − + CO 2 = CO 3 2− + H 2 O (1) II stage (bicarbonate formation) CO 3 2− + CO 2 + H 2 O =2HCO 3 − (2) ese side reactions have high significance for the proper functioning of FC, since the salts Na 2 CO 3 and NaHCO 3 (as well as the corresponding lithium and potassium salts) poorly dissolve in aqueous alkaline solutions. ese salts and their Hindawi Publishing Corporation Journal of Fuels Volume 2014, Article ID 670209, 10 pages http://dx.doi.org/10.1155/2014/670209
Transcript of Research Article Separate Determination of Borohydride...
Research ArticleSeparate Determination of Borohydride BorateHydroxide and Carbonate in the Borohydride Fuel Cell byAcid-Base and Iodometric Potentiometric Titration
A V Churikov S L Shmakov V O Romanova K V Zapsis A V UshakovA V Ivanishchev and M A Churikov
Institute of Chemistry Saratov State University 83 Astrakhanskaya Street Saratov 410012 Russia
Correspondence should be addressed to V O Romanova nikanor veronamailru
Received 23 May 2013 Accepted 26 November 2013 Published 29 January 2014
Academic Editor Cesar Sequeira
Copyright copy 2014 A V Churikov et alThis is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
A methodology for quantitative chemical analysis of the complex ldquoborohydride-borate-hydroxide-carbonate-waterrdquo mixtures usedas fuel in the borohydride fuel cell was developed and optimized The methodology includes the combined usage of the acid-baseand iodometric titration methods The acid-base titration method which simultaneously uses the technique of differentiation andcomputer simulation of titration curves allows one to determine the contents of hydroxide (alkali) carbonate and total ldquoborate +borohydriderdquo content The iodometric titration method allows one to selectively determine borohydride so the content of each ofOHminus BH
4
minus BO2
minus and CO3
2minus anions in the fuel becomes estimated The average determination error depends on the number andratio of compounds in a mixture Specific details of the analysis of various fuel mixtures are discussed
1 Introduction
The intense progress of electric vehicles portable electronicsmobile communication tools and other systems whichrequire independent power supply stimulates the design ofnew chemical power sources [1 2] These sources have topossess high-energy specific characteristics but also theymust be safe and comfortable in use In this connection thedevelopment of fuel cells (FC) in which chemical energy isdirectly converted into electrical one becomes most topicalEspecially direct borohydride fuel cells (DBFCs) are inten-sively evolved in which alkaline aqueous solutions of suchsalts as LiBH
4
NaBH4
and KBH4
are used as fuel [3ndash9]In these systems electrical energy is generated by meansof hydrolysis and electrochemical oxidation of borohydridesinto borates In alkaline media these are LiBO
2
NaBO2
and KBO
2
[10ndash12] whose solubility essentially influences thepower characteristics of FC [13ndash15] The difficulty of thedesign of effective and sustainable anode electrocatalysts forthe anodic oxidation of borohydride limits the efficiency andpower density attainable in these devices [16ndash18]
The fuel of DBFCs is a multiple mixture whose specificcharacteristics directly depend on the ratio of its components
BH4
minus
OHminusH2
O [19ndash24] It can be an aqueous solution ofNaOH andNaBH
4
in the initial state and an aqueous solutionof NaOH NaBH
4
and NaBO2
in the discharged (partiallyor fully) state Besides the fuel composition is changed dueto side reaction it can dry up or water out and it also canbe acidified andor carbonated by chemical interaction withcarbon dioxide from air In this case additional componentswill appear in the solution such as carbonate Na
2
CO3
andbicarbonate NaHCO
3
at deeper carbonization in accordancewith the ionic reactions
I stage (carbonate formation)
2OHminus + CO2
= CO3
2minus
+H2
O (1)
II stage (bicarbonate formation)
CO3
2minus
+ CO2
+H2
O = 2HCO3
minus (2)
These side reactions have high significance for the properfunctioning of FC since the salts Na
2
CO3
and NaHCO3
(aswell as the corresponding lithium and potassium salts) poorlydissolve in aqueous alkaline solutions These salts and their
Hindawi Publishing CorporationJournal of FuelsVolume 2014 Article ID 670209 10 pageshttpdxdoiorg1011552014670209
2 Journal of Fuels
crystal hydrates are deposited in the porous structure of theelectrodes to deteriorate them So it is important on the onehand to preserve the fuel from contact with CO
2
and on theother hand to control the carbonate concentration in it
In this connection for the development andmaintenanceof FCs regularmonitoring of the chemical composition of thefuel used is necessary It requires control of the concentrationof each dissolved component during the working processof FC determination of the discharge degree of the fueland evaluation of the conformity of the current state of thefuel mixture to its theoretical composition calculated frommaterial balance
Earlier a number ofmethods were proposed for quantita-tive determination of the total boron and boron compoundsin analyzed samples [25ndash31] To analyze borates and boricacid the titrimetric [28ndash31] photometric [32] and fluores-cent methods [33ndash35] have been suggested It is also possibleto carry out the selective determination of borohydrides bythe hydrogen volumetric method [36 37] titration [38ndash41]with permanganate [36] hypochlorite [42] iodate [10 43]and the voltammetric [44ndash46] or potentiometric [47ndash49]titration methods Titration of borohydride solutions withacid in particular HCl was suggested in a few papers [3640 50] where the reaction equation was written as
NaBH4
+HCl + 3H2
O = 4H2
+H3
BO3
+ NaCl (3)
In the case of potentiometric acid titration of aqueousNaBH4
solutions it is pointed [36] that actually it is sodium borateformed as a result of NaBH
4
hydrolysis which is titrated
BO2
minus
+H3
O+ = H3
BO3
(4)
Thus there is no unified method of quantitative analysisof boron-containing compounds and other anions presentedin the fuel solution of DBFC For selective determina-tion of each component it is necessary to consecutivelyapply several techniques In the present paper we havedeveloped a methodology for quantitative analysis of com-plex ldquoborohydride-borate-alkali-carbonate-waterrdquo mixturesbased on the methods of acid-base and iodometric titrationThe first method allows simultaneous estimation of thecontents of hydroxide carbonate and the ldquoborate + boro-hydriderdquo total with their joint presence in the sample Thesecondmethod allows selective determining the borohydridecontent
2 Experimental Section
The contents of hydroxide ions carbonate ions and totalborate and borohydride ions were determined by the acid-base titration method with a 01molsdotLminus1 HCl solution as thetitrant A fuel sample taken from FC for analysis is a highlyalkaline medium For acid-base titration it was repeatedlydiluted A sample of a certain weight (01 to 05 g) wastaken from the fuel analyzed quantitatively transferred toa 250mL glass for titration and brought to 1000mL withdistilled water A homogeneous solution with pH asymp 11ndash13resulted The analysis result was then recalculated in terms
of the initial fuel in view of the dilution factor A fixedinitial volume of the titratable mixture 119881
0
= 1000mL isrequired to further correct modeling of the titration curveTitration was started from some initial pH value and endedat pH asymp 2-3 The positions of peaks were defined and bothtitration curves (integral and differential) were saved in adata file for subsequent computer simulation To analyzeborohydride ions the iodometric redox titration methodwas used The analogous sample of the analyzed fuel (01to 05 g) was quantitatively transferred into a 50mL flaskand brought to the mark with a 1molsdotLminus1 NaOH solutionThen a 5mL aliquot was sampled transferred to a glassfor titration and brought to 50mL with a 1molsdotLminus1 NaOHor KOH solution with further titration with a 01molsdotLminus1standard iodine solution up to a preset potential value Anautomatic ATP-02 titrator (ldquoAquilonrdquo Russia) was appliedThe software package of the titrator provides titration up toa preset electrode potential value or pH at an automaticallychanged rate of the titrant A glass indicator electrode anda silver-chloride reference electrode were used for acid-basetitration a platinum indicator electrode and a glass referenceelectrode were applied for iodometric titration All analyseswere carried out under thermostating at 25∘C
Chemically pure reagents (reagent grade) were used toprepare reference solutions of a desired composition forchecking our analytical methodology The chemicals usedwere NaBO
2
sdot 4H2
O (Vecton Corp Russia the analyticalreagent content 119908NaBO
2
= 0490 plusmn 0003) KBO2
sdot 125H2
O(Vecton Corp the reagent content 119908KBO
2
= 0767 plusmn 0001)NaOH sdot 119909H
2
O (Ecros Corp Russia the reagent content119908NaOH = 0989 plusmn 0002 water content 119908H
2O = 001 plusmn
0003) KOH sdot 119909H2
O (Ecros Corp the reagent content119908KOH = 0898 plusmn 0003 water content 119908H
2O = 0101 plusmn
0003) NaBH4
(Aviabor Corp Russia the reagent content119908NaBH
4
= 0974 plusmn 0005) KBH4
(Aviabor Corp the reagentcontent 119908KBH
4
= 0971 plusmn 0006) and distilled water withoutdissolved carbon dioxide Every reagent had undergone com-mon chemical analysis to analyze the basic substance watercontent and carbonate content No analytically detectablecarbonate impurity in the solid reagents was found Theexact composition of the solid-state reagents was taken intoconsideration at preparing reference solutions The error ofeach controlled concentration of the reference solutions canbe estimated less than 15
3 Results and Discussion
31 Determination of Borohydride Borate Hydroxide andCarbonate by Acid-Based Titration The analyzed object wasan aqueous solution containing a mixture of anions OHminus +BO2
minus
+ BH4
minus
+ CO3
2minus in a random ratio as highly solublesodium and potassium salts During the titration processby an aqueous solution of acid the following reactionsproceed
OHminus +H+ = H2
O (5)
BH4
minus
+ 2H2
O H+997888997888rarr BO
2
minus
+ 4H2
uarr (6)
Journal of Fuels 3
BO2
minus
+H+ = HBO2
(7)
CO3
2minus
+H+ = HCO3
minus (8)
HCO3
minus
+H+ = H2
CO3
(9)
In the presence of BH4
minus the first stage is the irreversiblehydrolysis of BH
4
minus catalyzed with acid which is not con-sumed Protons are consumed at the second stage only(reaction (9)) As a result the total boron (BO
2
minus
+ BH4
minus) istitrated out at the acid-base titration
Reactions (5)ndash(9) proceed concurrently The predomina-tion of this or that reaction is determined by the ratio of thecorresponding dissociation constants of HBO
2
H2
CO3
andwaterH
2
OThis predomination changes as the titration curvegoes with gradual change of pH from the initial pH value asymp11ndash13 to the final one asymp 2-3 The values of the dissociationconstants are such [51 52] that at the addition of acid thefirst reactions (5) and (6) occur then the reactions (7) and (8)proceed and the titration process is completed with reaction(9) It should be noted that the reaction (7) is written ina simplified form as it is known about the existence ofa number of borate anion forms but the final product ofprotolysis is orthoboric acid H
3
BO3
This may be ignoredwithin our pH range
Borohydride hydrolysis reaction (6) takes place in aque-ous alkaline solutions even at high pH but its rate is extremelylow [21] Table 1 comprises approximate rates of BH
4
minus decom-position due to hydrolysis at 25∘C One can see that thehydrolysis of BH
4
minus slowly proceeds at pH asymp 11ndash13 in thesolutions at acid-base titration but this hydrolysis is part ofthe analytical procedure Hydrolysis is sharply acceleratedat pH asymp 7ndash9 and the borate ions formed are further boundin reaction (7) No complex mechanism of the protolysis ofBH4
minus ions [8 21 34] is reflected on the titration curve pHversus 119881
119905
Let us assume that the initial aqueous solution has a
volume 1198810
containing 119899OHminus of alkali 119899BH4
minus of borohydride119899BO2
minus of metaborate and 119899CO3
2minus of carbonate Hydrocar-bonate cannot exist in the initial (highly alkaline) solutionthat is 119899HCO
3
minus = 0 The formation and consumption of verysmall amounts of water during the neutralization reactionare neglected but the dilution degree of the initial mixturetitrant is taken into account The titrant (119905) is an aqueousHCl solution with a concentration 119873
119905
to be added into themixture at the current time in the amount119881
119905
mLThen takinginto account the titrant-caused dilution the overall molarconcentrations 119862
119894
are
119862119905
=119873119905
119881119905
119881 (10)
119862alc =119899OHminus
119881 119862
119861
=119899BH4
minus + 119899BO2
minus
119881 119862carb =
119899CO3
2minus
119881
(11)
Here119881 = 1198810
+119881119905
is the total volume of the mixture at the cur-rent instant of titration Unlike the overall concentrations 119862
119894
the current equilibrium values of the molar concentrations[H+] [OHminus] [BH
4
minus] [BO2
minus] [CO3
2minus] [HCO3
minus] [HBO2
]
Table 1 Approximate rates of borohydride ion BH4
minus decompositiondue to hydrolysis at 25∘C
Concentration [OHminus] or pH Initial rate of BH4
minus decomposition233molsdotLminus1 lt01sdotdayminus1
pH = 13 asymp15sdotdayminus1
pH = 11 asymp7sdothr minus1
pH = 9 asymp02sdotsminus1
pH = 7 gt10sdotsminus1
and [H2
CO3
] are marked with symbols in square bracketsand they are calculated from the equilibrium constants of thetitration reactions
An additional correction is taken into account for theaverage ionic activity coefficient We used the 2nd approxi-mation of Debye-Huckelrsquos theory as Gyuntelbergrsquos equationwhere the activity coefficient is only determined by the ionicstrength of the solution and the squared ion charges [53]Then 119891 is the activity coefficient of all single-charged ionsbut in the equations containing the double-charged carbonateion concentration the factor 1198914 will appear Gyuntelbergrsquosequation at 25∘C looks like
lg119891 = minus05092radic119868
1 + radic119868 (12)
where 119868 = 05sum119894
119888119894
1199112
119894
is the ionic strength of the solutioncalculated by the formula in our case
119868 = 05 times 119862119905
+ 119862alc + 119862119861 + 2 times 119862carb
+ [H+] + [OHminus] + [BH4
minus
] + [BO2
minus
]
+ [HCO3
minus
] + 4 times [CO3
2minus
]
(13)
Gyuntelbergrsquos equation has an advantage over other approx-imations of having no arbitrary parameters and describingwell electrolyte solutions when 119868 asymp 01 which is the casein our acid-base titration (the concentration of any ionsin solution at different stages of titration did not exceed01molsdotLminus1) The concentration of solutions was chosen so asnot to blur steps on the titration curve and at the same timethe correction to the activity coefficients should be small
As a result with the experimental data arrays 119881119905
pH119889pH119889119881
119905
and using (10) and (11) we obtain the data arrays119862119905
119862119861
119862alc and 119862carb The current values of the equilibriumconcentrations at every titration point can be calculated fromthe conditions of chemical equilibrium and material balanceby means of the appropriate formulae
[OHminus] =119870119882
1198912 [H+]
[BH4
minus
] + [BO2
minus
] =119862119861
1 + 1198912 [H+] 119870119861
[CO3
2minus
] =119862carb
1 + (1198914 [H+] 1198702
) (1 + 1198912 [H+] 1198701
)
4 Journal of Fuels
[HCO3
minus
] =119862carb
1 + 1198912 [H+] 1198701
+ 1198702
1198914 [H+]
[H2
CO3
] =119862carb
1 + (1198701
1198912 [H+]) (1 + 1198702
1198914 [H+])
(14)
where
[H+] = 119891minus110minuspH (15)
Here the ionic product of water (autoprotolysis constant)is 119870119882
= 1198912 [OH]sdot[H] = 1 times 10
minus14 at 25∘C [52] thedissociation constant of metaboric acid HBO
2
is 119870B =
1198912
(([BO2
] sdot [H])[HBO2
]) the dissociation constant ofcarbonic acid H
2
CO3
at the first stage is 1198701
= 1198912
(([HCO3
] sdot
[H])[H2
CO3
]) = 445 times 10minus7 at 25∘C [52] the dissociation
constant of carbonic acid H2
CO3
at the second stage is 1198702
=
1198914
(([CO3
] sdot [H])[HCO3
]) = 469 times 10minus11 at 25∘C [52]
Moreover processing the titration curves of simple solutionsof a fixed composition (eg 001molsdotLminus1 NaBO
2
) can be usedfor refinement of these dissociation constants
Let us determine the calculated volume 119881calc of thetitrant from the material balance by acid by boron andby carbon only considering the acid consumption by thetitration reactions (5) (7)ndash(9)Thematerial balance equationis thus written as
119862119905
= [H+] + (119862alc minus [OHminus
])
+ [HBO2
] + [HCO3
minus
] + 2 times [H2
CO3
] (16)
(the initial content of acid in an alkaline solution [H+]0 lt10minus11molsdotLminus1 is ignored)The calculated value of119881calc is estimated from the current
pH value and (10) and (15) As a result the calculated pointsof the titration curve of solutions containing a mixture ofanions OHminus BH
4
minus BO2
minus and CO3
2minus are determined by theequation
119881calc =119881
119873HCl([H+] + Calc minus [OH
minus
] + 119862119861
minus [BH4
minus
]
minus [BO2
minus
] + [HCO3
minus
] + 2 times [H2
CO3
])
(17)
where the current equilibrium values ofmolar concentrationsare determined by (14) and (15) Equation (17) is veryconvenient for computer simulations It allows calculatingthe pH minus 119881calc dependence and plotting the whole calculatedtitration curve By means of fitting the calculated curve to theexperimental curve we find the amounts of components inthe sample 119899OHminus 119899BH
4
minus+BO2
minus and 119899CO3
2minus The concentrationof borate is calculated by the difference of total boron minusborohydride that is 119899BO
2
minus = 119899BH4
minus+BO2
minus minus 119899BH4
minus The amountof borohydride in the mixture is selectively determined byiodometric titration
32 Determination of Borohydride in Solution by IodometricTitration As shown in [39] the quantification of BH
4
minus
in solution by direct iodometric titration is based on thereaction proceeding quantitatively in an alkaline medium
4I2
+ BH4
minus
+ 8OHminus = BO2
minus
+ 8Iminus + 6H2
O (18)
Usually the direct titration is made in a low alkaline medium(pH lt 11) because iodine interacts with hydroxide ions toform nonactive iodate ion IO
3
minus in higher alkaline solution[34]
3I2
+ 6OHminus 997888rarr IO3
minus
+ 5Iminus + 3H2
O (19)
However borohydride ions are insufficiently stable atroom temperature when pH lt 11 Table 1 comprises approx-imate rates of BH
4
minus decomposition due to hydrolysis Onecan see that the fuel with alkalinity above 2molsdotLminus1 is almostnot subjected to hydrolysis at 25∘C The same applies to theiodometric redox titrationmethod used by us which requiresa 1molsdotLminus1 NaOH solution In a 1molsdotLminus1 alkaline solutionthe addition of iodine to borohydride is also accompanied byextremely slight hydrogen release as a result of borohydridedecomposition Under these conditions about 05ndash1 ofBH4
minus ions is decomposed while a negligible amount ofiodate is formed by reaction (18) with iodine consumptionof sim05ndash1 Thus any mistakes are compensated and directiodometric titration allows one to obtain the result closest tothe true value of borohydride concentration (the error not toexceed 005)
33 Processing Titration Curves and Estimation of AccuracyThe titration curves pH versus119881
119905
and the appropriate depen-dences 119889pH119889119881
119905
versus 119881119905
obtained by acid-base titration ofaqueous solutions of various anion mixtures are shown inFigure 1 and the analogous curves obtained by iodometrictitration are shown in Figure 2 The first distinct step pre-sented (not always) on the iodometric titration curve reflectsa complex mechanism of the chemical reaction (18) and isneglected The determination of the amount of the titrantis carried out by the second sharp leap within the potentialrange 0 to 600mV (Figure 2)
The titration curves were processed by two ways namelya simple method of differentiation and a more complexmethod of computer simulations For the iodometric deter-mination of borohydride it is enough to use the method ofdifferentiation only while for acid-base titration the bestresults are obtained when both methods (differentiation andsimulation) are used
Themethod of differentiation is based on the equivalencepoints coinciding with the inflections on the pH versus119881119905
curve and with appropriate maxima on the differential119889pH119889119881
119905
versus 119881119905
curve (Figure 1) The positions of themaximum points 119881lowast
119905
are fixed the titrant volume consumedfor titration of the 119894th component Δ119881lowast
119905
= 119881lowast
119905119894
minus 119881lowast
119905119894minus1
ismeasured and the amount of each component is calculatedHowever in few complex cases it is possible to state thatan extreme point on the differential 1198892pH119889(119881
119905
)2 = 0 curve
is close to an equivalence point at sharp changes of pH Ifsmoothed inflections with a small pH difference are observedor two points of inflection are near each other a significantsystematic error arises
The method of simulation is based on the theoryexplained aboveThe program for calculating titration curvesuses the appropriate theoretical equations (10)ndash(17) and com-bines the experimental pH versus119881
119905
curvewith the calculated
Journal of Fuels 5
0
2
4
6
8
10
12
14
0 4 8 12
pH
ExperimentCalculationDifferentiation
Vt (mL)
minus100
900
1900
2900
3900
4900
dpH
dVt
OH minus
(a)
0
20
40
60
80
100
120
0
2
4
6
8
10
12
14
0 2 4 6 8 10 12 14
pH
ExperimentCalculationDifferentiation
Vt (mL)
dpH
dVt
OHminus+ CO3
2minus
(b)
0
20
40
60
80
100
120
0
4
8
12
16
0 1 2 3 4 5 6
pH
ExperimentCalculationDifferentiation
Vt (mL)
dpH
dVt
OHminus+ BH4
minus+ BO2
minus
(c)
20
0
40
60
80
100
120
0
2
4
6
8
10
12
14
0 2 4 6 8
pH
ExperimentCalculationDifferentiation
Vt (mL)
dpH
dVt
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
(d)
Figure 1 Calculated titration curves experimental titration curves and the corresponding 119889pH119889119881119905
versus 119881119905
curves for aqueous solutionsof several mixtures of anions (a) OHminus (b) OHminus + CO
3
2minus (c) OHminus + BH4
minus or OHminus + BO2
minus or OHminus + BH4
minus
+ BO2
minus (d) OHminus + BH4
minus
+
BO2
minus
+ CO3
minus
pH versus 119881calc one The variable parameters are the soughtquantities of components in the aliquot 119899OHminus 119899BH
4
minus+BO2
minus and119899CO3
2minus The criterion of optimum is the minimum dispersion
1198782
=sum119870
119896=1
(pH119896
minus pHcalc119896)2
119870 minus 1
=sum119870
119896=1
((119889pH119889119881119905119896
) (119881119905119896
minus 119881calc119896))2
119870 minus 1
(20)
Here119870 is the number of points on the titration curve Figure 1shows the experimental and calculated titration curves forfew solutions of various multicomponent mixtures It is
visible that the applied computational methods allow exactsimulating experimental curves
Error Analysis and Estimation of AccuracyAnumber of refer-ence solutions of a desired composition were prepared usingKBO2
NaBH4
KBH4
NaOHKOHNa2
CO3
andK2
CO3
forvalidation of our analytical methodology (the concentrationranges of each analyzed ion in the considered samples arepresented in Table 2) In order to detect systematic errorsthe dependences of the ldquomeasuredweightedrdquo ratios on theanionic fraction 120596
119894
were plotted (120596119894
is the mole fraction ofthe 119894th anion in the total amount of the analyzed anions 120596varies from 0 up to 1) The results are given in Figure 3 Theaverage value of the ldquomeasuredweightedrdquo ratio for each ionis presented in Table 3
6 Journal of Fuels
Table 2 Considered concentration ranges of analyzed ions in thesample
Ion Concentration range in the analyzed sample molsdotLminus1
OHminus 002ndash12BH4
minus 002ndash02BO2
minus 005ndash02CO3
2minus 0008ndash01
It is apparent from Table 3 that the simulation methodalso gives a systematic error The causes can be simplificationof the theory the impossibility to consider all side processesthe inability to exactly calculate activity coefficients and soforth so the shape of the calculated curve may not com-pletely coincide with the experimental curve In particularin the titration process of borate solutions the formationof poliborates and their hydrated forms is possible In thecase of simulation the lower branch of the titration curveshould be limitedwhen all equivalence points are passed overAccelerated titration or cold solutionmay cause an additionalerror due to the inhibition of reaction (6) and the failure ofchemical equilibrium
The concentration of OHminus ions is estimated with an accu-racy of 0959 and 0956 for the differentiation and simulationmethods respectivelyThe total of (BH
4
minus
+BO2
minus) is estimatedwith an accuracy of 1023 and 1012 for the differentiationand simulation methods respectively (Table 3) Thus for theOHminus+BH
4
minus
+BO2
minus system the differentiation and simulationmethods give similar results and have no advantages overeach other and the systematic error is small but naturallyincreases with decreasing share of the analyzed ionThe trendof the systematic error is shown in Figure 3(a) by means ofsolid lines Both methods overestimate the content of boronin the sample and underestimate the content of alkali Forcompensation of the systematic error the following equationshave been obtained for the method of differentiation
120573OHminus = [138 minus 04120596minus005
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [120596minus005
BH4
minus+BO2
minus minus 0025]minus1
(21)
and for the method of simulation
120573OHminus = [139 minus 04120596minus008
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [07120596minus005
BH4
minus+BO2
minus + 028]minus1
(22)
After analysis and the determination of the components119899OHminus and 119899BH
4
minus+BO2
minus a correction procedure was carried outby multiplying the values 119899
119894
found by the correspondingcorrection coefficients 120573
119894
calculated from formulae (21) or(22) Finally the corrected amounts of the 119894th component inthe sample 119899
119894cor are
119899119894cor = 120573119894119899119894 (23)
Figure 3(b) shows the result of correction of the data given inFigure 3(a)The systematic error was totally compensated forall the variants of analysis (Table 3)
0 2 4 6 8 10Vt (mL)
minus600
minus200
200
600
1000
E(m
V)
Vlowastt
minus27000
minus18000
minus9000
0
9000
dEdVt
Figure 2 Curve of direct iodometric titration of borohydride ionsin an aqueous solution with the mixture of anions OHminus + BH
4
minus
+
BO2
minus
+ CO3
2minus (119881lowast119905
is equivalence point)
When the value of the anionic fraction 04 lt 120596119894
lt 1 allpoints lie within the ldquomeasuredweightedrdquo range 095ndash105that is the random error does not exceed 5 all points liewithin the range 088ndash112 when 005 lt 120596
119894
lt 04 that isthe random error does not exceed 12 It is only possibleto perform semiquantitative analysis of any component at itsvery small content in the mixture (120596
119894
lt 002) On correctionthe average accuracy parameter of the OHminus concentrationis 1000 for differentiation and 1001 for simulation and theaverage accuracy parameter for the (BH
4
minus
+ BO2
minus
) total is1008 for differentiation and 1004 for simulation (Table 3)
The feature of titration of alkaline-carbonate solutionsis the existence of three leaps on the titration curve(Figure 1(b))The first leap belongs to alkali while the secondand third ones are due to carbonates Correspondingly whenthe quantities of components are determined by the locationof peaks on the differential curve the quantity of CO
3
2minus isincluded twiceThe analysis of carbonate bymeans of the sec-ond peak gives a worse result than by the third one At a verysmall content of carbonate the second peak is not detectedThe average ldquomeasuredweightedrdquo value is 1215 for CO
3
2minus
ions by the second peak on the differential curve and 1115in the case of the third peak and the ldquomeasuredweightedrdquovalue is 1089 for the method of simulation The results ofcontrol determination of the alkali and carbonate contents inthe reference solutions OHminus + CO
3
2minus are shown in Figures3(c) and 3(d) for the two methods as the dependence ofthe accuracy parameter on the anionic fractions 120596
119894
In allcases the points of differentiation are more distant fromthe ldquocorrectrdquo level than those of simulation Consequentlythe method of simulation gives more correct results for theOHminus + CO
3
2minus system while the method of determinationcannot be recommended because of its high systematic errorsin carbonate analysis
The systematic error naturally increases with decreasingfractions of the analyzed ions In Figure 3(c) the trend ofsystematic errors is shown by means of solid lines for the
Journal of Fuels 7
Table 3 Average values of the ldquomeasuredweightedrdquo ratios for each ion in the mixture before and after correction of systematic errors
System Ions Method ldquoMeasuredweightedrdquo ratioBefore correction After correction
OHminus + BH4
minus + BO2
minus
OHminus Differentiation 0959 1000Simulation 0956 1001
BH4
minus + BO2
minus
Differentiation 1023 1008Simulation 1012 1004
OHminus + CO3
2minus
OHminus Simulation 0985 1003CO3
2minus Simulation 1089 0996
OHminus + BH4
minus + BO2
minus + CO3
2minus
OHminus Simulation 0874 0958BH4
minus + BO2
minus Simulation 1040 0992CO3
2minus Simulation 0934 1008
08
09
1
11
12
13
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ BH4
minus+ BO2
minus
OHminus simulationBH4
minus+ BO2
minus simulationNormOHminus differentiationBH4
minus+ BO2
minus differentiation
(a)
08
09
1
11
12
13
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ BH4
minus+ BO2
minus
OHminus simulationBH4
minus+ BO2
minus simulation + correctionNormOHminus differentiation + correctionBH4
minus+ BO2
minus differentiation + correction
(b)
05060708091
1112131415
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ CO3
2minus
OHminus simulation
NormCO3
2minus simulation
(c)
07
08
09
1
11
12
13
14
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ CO3
2minus
simulation + correctionOHminus
Normsimulation + correctionCO3
2minus
(d)
0
02
04
06
08
1
12
14
0 02 04 06 08 1
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
OHminus simulationBH4
minus+ BO2
minus simulationNormOHminus differentiation
CO32minus simulation
CO32minus differentiation
120596i
Measuredweighted
BH4minus+ BO2
minus+ CO3
2minus differentiation
(e)
Measuredweighted
02
04
06
08
1
12
14
0 02 04 06 08 1120596i
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
BH4minus+ BO2
minus simulation + correctionOHminus simulation + correction
Normsimulation + correctionCO3
2minus
(f)
Figure 3 Dependence of the ldquomeasuredweightedrdquo ratios for anions on their mole fraction 120596119894
in the mixture (a) for the OHminus + BH4
minus
+
BO2
minus system before correction of systematic errors (b) for the OHminus + BH4
minus
+ BO2
minus system after correction of systematic errors (c) for theOHminus +CO
3
2minus system before correction of systematic errors (d) for the OHminus +CO3
2minus system after correction of systematic errors (e) for theOHminus + BH
4
minus
+ BO2
minus
+CO3
2minus system before correction of systematic errors (f) for the OHminus + BH4
minus
+ BO2
minus
+CO3
2minus system after correctionof systematic errors The solid lines show the average trend of errors The dotted lines show the error interval for the method of simulation
8 Journal of Fuels
method of simulation The following equations have beensuggested for compensation of this trend
120573OHminus = [29 minus 19120596minus0055
OHminus ]minus1
120573CO3
2minus = [75120596minus001
CO3
2minus minus 65]minus1
(24)
After analysis and the determination of the 119899OHminus and 119899CO3
2minus
values a correction procedure is carried out by formula(24) Figure 3(d) shows the result of such correction Thesystematic error is completely compensated (Table 3) Allpoints lie within the ldquomeasuredweightedrdquo range 095ndash105for the anionic fractions within 04 lt 120596
119894
lt 1 that is therandom error does not exceed 5 and the random scatteringdoes not exceed 12 when 015 lt 120596
119894
lt 04 If the fractionof carbonate is less than 015 the reliability of its analysisdecreases because of the high random dispersion thereforeit is required to increase the number of replicate samplesThedirect titrimetric analysis of carbonate becomes impossiblewhen 120596CO
3
2minus lt 0015A feature of titration of alkaline-borohydride-borate-
carbonate solutions is the existence of three weak leaps onthe titration curve (Figure 1(d)) The first leap belongs toalkali while the second belongs to the ldquoBH
4
minus
+ BO2
minus
+
CO3
2minusrdquo total and the third one belongs to carbonate ionsRespectively at the quantification of components by meansof the position of peaks on the differential curve the totalcontent of boron 119899BH
4
minus+BO2
minus can be only calculated after thedetermination and extraction of the carbonate quantity
The results of our control determination of the anioncontents in the OHminus + BH
4
minus
+ BO2
minus
+ CO3
2minus mixturesby both methods are shown in Figure 3(e) The methodof differentiation gives an unsatisfactory result for car-bonate underestimating its content significantly the meanldquomeasuredweightedrdquo value being 0615 The carbonate peakdisappears when 120596CO
3
2minus lt 015 which leads to incorrectdetermination of the BH
4
minus
+ BO2
minus total Therefore for theOHminus+ BH
4
minus
+ BO2
minus
+ CO3
2minus system (the highly carbonatedand discharged fuel) the method of differentiation cannotbe recommended because of its large systematic errors incarbonate analysis and the method of simulation is onlysuggested for use The mean ldquomeasuredweightedrdquo values areshown in Table 3 The determination accuracy is 0874 forOHminus ions 1040 for the BH
4
minus
+ BO2
minus total and 0934 forCO3
2minus ions After correction these parameters become 09580992 and 1008 respectively The correcting coefficients are
120573OHminus = [198 minus 120596minus005
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [120596minus0085
BH4
minus+BO2
minus minus 003]minus1
120573CO3
2minus = [195 minus 120596minus001
CO3
2minus]minus1
(25)
The systematic error is thus compensated however therandom scattering of the points is higher than with moresimple options The random dispersion for alkali and borondoes not exceed 15 (all points arewithin 085ndash115) howeverit is only fair for carbonatewhen120596CO
3
2minus gt 01 If the carbonate
content is less than 01 its semiquantitative analysis is onlypossible But very small amounts of carbonate will not affectthe functioning of DBFC and only higher concentrations ofcarbonate exceeding the solubility limit can be deposited inthe electrode to hinder the functioning of DBFC
4 Conclusions
Theanalytic technique presented in our paper includes takinga small fuel sample from DBFC and performing two types oftitrations (acid-base and iodometric ones) which supplementeach otherThenecessity of exactly two techniques of titrationis due to the fact that iodometric titration determines theBH4
minus quantity in the sample only while the quantities ofother fuel components are provided by acid-base titration(OHminus BO
2
minus CO3
2minus)Therefore the joint application of thesetitration techniques allows one to most fully quantify thecurrent state of fuel in the process of DBFC functioningThe determination correctness of the technique has beenshown on artificial mixtures with a wide variation of theircomposition The average error depends on the number ofcomponents and their ratio in the mixture The investigationresults show that in the most complex case of highly carbon-ated and discharged fuel the maximal error of determinationdoes not exceed 15
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgment
The authors would like to gratefully acknowledge the RussianFoundation for Basic Research for financial support (Projectno 12-03-31802)
References
[1] J B Lakeman A Rose K D Pointon et al ldquoThe directborohydride fuel cell for UUV propulsion powerrdquo Journal ofPower Sources vol 162 no 2 pp 765ndash772 2006
[2] C P de Leon F C Walsh D Pletcher D J Browning and JB Lakeman ldquoDirect borohydride fuel cellsrdquo Journal of PowerSources vol 155 no 2 pp 172ndash181 2006
[3] R Aiello J H Sharp and M A Matthews ldquoProduction ofhydrogen from chemical hydrides via hydrolysis with steamrdquoInternational Journal of Hydrogen Energy vol 24 no 12 pp1123ndash1130 1999
[4] S C Amendola S L Sharp-Goldman M S Janjua et al ldquoSafeportable hydrogen gas generator using aqueous borohydridesolution and Ru catalystrdquo International Journal of HydrogenEnergy vol 25 no 10 pp 969ndash975 2000
[5] H I Schlesinger H C Brown A E Finholt J R GilbreathH R Hoekstra and E K Hyde ldquoSodium borohydride itshydrolysis and its use as a reducing agent and in the generationof hydrogenrdquo Journal of the American Chemical Society vol 75no 1 pp 215ndash219 1953
Journal of Fuels 9
[6] S C Amendola P Onnerud M T Kelly P J Petillo S LSharp-Goldman and M Binder ldquoNovel high power densityborohydride-air cellrdquo Journal of Power Sources vol 84 no 1 pp130ndash133 1999
[7] B H Liu and Z P Li ldquoCurrent status and progress of directborohydride fuel cell technology developmentrdquo Journal ofPower Sources vol 187 no 2 pp 291ndash297 2009
[8] B H Liu and Z P Li ldquoA review hydrogen generation fromborohydride hydrolysis reactionrdquo Journal of Power Sources vol187 no 2 pp 527ndash534 2009
[9] B Weng Z Wu Z Li H Yang and H Leng ldquoHydrogengeneration from noncatalytic hydrolysis of LiBH4NH3BH3mixture for fuel cell applicationsrdquo International Journal ofHydrogen Energy vol 36 no 17 pp 10870ndash10876 2011
[10] A E Sanli I Kayacan B Z Uysal and M L Aksu ldquoRecoveryof borohydride from metaborate solution using a silver catalystfor application of direct rechargable borohydrideperoxide fuelcellsrdquo Journal of Power Sources vol 195 no 9 pp 2604ndash26072010
[11] R Jamard J Salomon A Martinent-Beaumont and CCoutanceau ldquoLife time test in direct borohydride fuel cellsystemrdquo Journal of Power Sources vol 193 no 2 pp 779ndash7872009
[12] J-H Wee ldquoA comparison of sodium borohydride as a fuel forproton exchange membrane fuel cells and for direct borohy-dride fuel cellsrdquo Journal of Power Sources vol 155 no 2 pp329ndash339 2006
[13] A V Churikov K V Zapsis V V Khramkov M A ChurikovM P Smotrov and I A Kazarinov ldquoPhase diagrams of theternary systems NaBH
4
+ NaOH + H2
O KBH4
+ KOH + H2
ONaBO
2
+ NaOH + H2
O and KBO2
+ KOH + H2
O at minus10∘CrdquoJournal of Chemical and Engineering Data vol 56 no 1 pp 9ndash13 2011
[14] A V Churikov K V Zapsis V V Khramkov M A Churikovand I M Gamayunova ldquoTemperature-induced transformationof the phase diagrams of ternary systems NaBO
2
+ NaOH+ H2
O and KBO2
+ KOH + H2
Ordquo Journal of Chemical andEngineering Data vol 56 no 3 pp 383ndash389 2011
[15] A V Churikov K V Zapsis A V Ivanishchev and V OSychova ldquoTemperature-induced transformation of the phasediagrams of ternary systems NaBH
4
+ NaOH +H2
O and KBH4
+ KOH + H2
Ordquo Journal of Chemical and Engineering Data vol56 no 5 pp 2543ndash2552 2011
[16] G Rostamikiaa and M J Janik ldquoDirect borohydride oxidationmechanism determination and design of alloy catalysts guidedby density functional theoryrdquo Energy amp Environmental Sciencevol 3 pp 1262ndash1274 2010
[17] B Sljuki J Miliki D M F Santosa and C A C SequeiraldquoCarbon-supported Pt
075
M025
(M = Ni or Co) electrocatalystsfor borohydride oxidationrdquo Electrochim Acta vol 107 pp 577ndash583 2013
[18] B H Liu J Q Yang and Z P Li ldquoConcentration ratio of[OHminus][BH
4
minus] a controlling factor for the fuel efficiency ofborohydride electro-oxidationrdquo International Journal of Hydro-gen Energy vol 34 no 23 pp 9436ndash9443 2009
[19] A V Churikov A V Ivanishchev I M Gamayunova andA V Ushakov ldquoDensity calculations for (Na K)BH
4
+ (NaK)BO
2
+ (Na K)OH + H2
O solutions used in hydrogen powerengineeringrdquo Journal of Chemical and Engineering Data vol 56no 11 pp 3984ndash3993 2011
[20] A V Churikov V O Romanova M A Churikov and I MGamayunova ldquoThemodel of fuel transformation at discharge of
direct borohydride fuel cellrdquo International Review of ChemicalEngineering vol 4 pp 263ndash268 2012
[21] A V Churikov I M Gamayunova K V Zapsis M AChurikov and A V Ivanishchev ldquoInfluence of temperature andalkalinity on the hydrolysis rate of borohydride ions in aqueoussolutionrdquo International Journal of Hydrogen Energy vol 37 no1 pp 335ndash344 2012
[22] Z P Li B H Liu K Arai and S Suda ldquoA fuel cell developmentfor using borohydrides as the fuelrdquo Journal of the Electrochemi-cal Society vol 150 no 7 pp A868ndashA872 2003
[23] Y Wang P Hea and H Zhou ldquoA novel direct borohydridefuel cell using an acid-alkaline hybrid electrolyterdquo Energy ampEnvironmental Science vol 3 no 10 pp 1515ndash1518 2010
[24] J Ma N A Choudhury and Y Sahai ldquoA comprehensive reviewof direct borohydride fuel cellsrdquo Renewable and SustainableEnergy Reviews vol 14 no 1 pp 183ndash199 2010
[25] R Bruhlmann and L Piatti ldquoAn improved method for thetitrimetric determination of boron in ironrdquo Chimia vol 11 p203 1957
[26] A Keshan and C Bimba ldquoCobalt-potassium and ammonium-cobalt dodecaboraterdquo Izvestiya Akademii Nauk Latvijskoj SSRp 115 1954
[27] J Czakow T Steciak and O Szczebinska ldquoThe spectral deter-mination of trace amounts of impurities in the solutions withthe metal electrodes in the spark moderdquo Analytical Chemistryvol 3 p 745 1958
[28] R Rosotti ldquoA fast method for the determination of traceamounts of boron in the steelrdquo Analytical Chemistry vol 44 p208 1962
[29] J Varka and A Sklaf ldquoApplication of potentiometric titrationIV Determination of B
2
O3
in glass enamels and boron-containing raw materialsrdquo Keramik vol 7 p 12 1957
[30] D E Williams and J Vilamis ldquoStability of the curcumincomplex in boron determinationrdquoAnalytical Chemistry vol 33pp 1098ndash1100 1961
[31] S Kertes and M Lederer ldquoPaper chromatography of inorganicions Rf values in mixtures of butanol and Hbrrdquo AnalyticaChimica Acta vol 15 no C pp 543ndash547 1956
[32] A A Nemodruk and Z K Karalova The Analytical Chemistryof Boron Nauka 1964
[33] C A Parker ldquoRaman spectra in spectrofluorimetryrdquo The Ana-lyst vol 84 no 1000 pp 446ndash453 1959
[34] C A Parker and W J Barnes ldquoFluorimetric determination ofboron application to silicon sea water and steelrdquo The Analystvol 85 no 1016 pp 828ndash838 1960
[35] M V Akhmanova Methods of Determination and Analysis ofRear Elements Izdat Akademija Nauk SSSR 1961
[36] E H Jensen A Study on Sodium Borohydride Nyt NordiskForlag Amold Busck Copenhagen Denmark 1954
[37] I Fatt and M Tashima Alkali Metal Dispersions D VanNostrand Co Inc Princeton NJ USA 1961
[38] DA Lyttle EH Jensen andWA Struck ldquoA simple volumetricassay for sodium borohydriderdquo Analytical Chemistry vol 24no 11 pp 1843ndash1844 1952
[39] P K Norkus ldquoIodometric determination of borohydriderdquoRussian Journal of Analytical Chemistry vol 23 pp 908ndash9111968
[40] N N Malrsquoceva and V S Khain Sodium Borohydride Propertiesand Application Nauka 1985
10 Journal of Fuels
[41] C Harzdorf and O Steinhauser ldquoZur photometrisehen Titra-tion von Fluorid mit Thoriumnitratrdquo Freseniusrsquo Zeitschrift furAnalytische Chemie vol 210 no 2 pp 106ndash112 1965
[42] W D Davis L S Mason and G Stegeman ldquoThe heats offormation of sodium borohydride lithium borohydride andlithium aluminum hydriderdquo Journal of the American ChemicalSociety vol 71 no 8 pp 2775ndash2781 1949
[43] S W Chaikin ldquoDirect volumetric assay of sodium borohydrideand potassium borohydriderdquo Analytical Chemistry vol 25 no5 pp 831ndash832 1953
[44] U Ulku and G Somer ldquoDetermination of trace borohydride inbasic solutions using differential pulse polarographyrdquo TurkishJournal of Chemistry vol 33 pp 657ndash665 2009
[45] H Celikkan H Aydin and M L Aksu ldquoThe electroanalyticaldetermination of sodium borohydride using a gold electroderdquoTurkish Journal of Chemistry vol 29 pp 519ndash524 2005
[46] M V Mirkin and A J Bard ldquoVoltammetric method forthe determination of borohydride concentration in alkalineaqueous solutionsrdquoAnalytical Chemistry vol 63 no 5 pp 532ndash533 1991
[47] D M F Santos and C A C Sequeira ldquoPotentiometric moni-toring of sodium borohydride in aqueous solutionsrdquo Ciencia sTecnologia dos Materials vol 20 no 3-4 pp 31ndash34 2008
[48] D M F Santos and C A C Sequeira ldquoSodium borohydridedetermination by measurement of open circuit potentialsrdquoJournal of Electroanalytical Chemistry vol 627 pp 1ndash8 2009
[49] H C Brown and A C Boyd Jr ldquoArgentimetric procedure forborohydride determinationrdquo Analytical Chemistry vol 27 no1 pp 156ndash158 1955
[50] V B Breicis A O Berzina and L K Lepin ldquoPotentiomet-ric titration of water solutions of sodium borohydride byhydrochloric acidrdquo Scientific Short Letter of Riga PolytechnicInstitute vol 15 pp 179ndash188 19651966
[51] U U Lurie Handbook on Analytical Chemistry Khimiya 1979[52] R A Lidin L L Andreeva and V A Molochko Hand-
book of Inorganic Chemistry Constants of Inorganic SubstancesKhimiya 1987
[53] R A Robinson and R H Stokes Electrolyte Solutions the Mea-surement and Interpretation of Conductance Chemical Potentialand Diffusion in Solutions of Simple Electrolytes ButterworthsLondon UK 1959
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
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StructuresJournal of
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
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Wind EnergyJournal of
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Nuclear EnergyInternational Journal of
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High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
2 Journal of Fuels
crystal hydrates are deposited in the porous structure of theelectrodes to deteriorate them So it is important on the onehand to preserve the fuel from contact with CO
2
and on theother hand to control the carbonate concentration in it
In this connection for the development andmaintenanceof FCs regularmonitoring of the chemical composition of thefuel used is necessary It requires control of the concentrationof each dissolved component during the working processof FC determination of the discharge degree of the fueland evaluation of the conformity of the current state of thefuel mixture to its theoretical composition calculated frommaterial balance
Earlier a number ofmethods were proposed for quantita-tive determination of the total boron and boron compoundsin analyzed samples [25ndash31] To analyze borates and boricacid the titrimetric [28ndash31] photometric [32] and fluores-cent methods [33ndash35] have been suggested It is also possibleto carry out the selective determination of borohydrides bythe hydrogen volumetric method [36 37] titration [38ndash41]with permanganate [36] hypochlorite [42] iodate [10 43]and the voltammetric [44ndash46] or potentiometric [47ndash49]titration methods Titration of borohydride solutions withacid in particular HCl was suggested in a few papers [3640 50] where the reaction equation was written as
NaBH4
+HCl + 3H2
O = 4H2
+H3
BO3
+ NaCl (3)
In the case of potentiometric acid titration of aqueousNaBH4
solutions it is pointed [36] that actually it is sodium borateformed as a result of NaBH
4
hydrolysis which is titrated
BO2
minus
+H3
O+ = H3
BO3
(4)
Thus there is no unified method of quantitative analysisof boron-containing compounds and other anions presentedin the fuel solution of DBFC For selective determina-tion of each component it is necessary to consecutivelyapply several techniques In the present paper we havedeveloped a methodology for quantitative analysis of com-plex ldquoborohydride-borate-alkali-carbonate-waterrdquo mixturesbased on the methods of acid-base and iodometric titrationThe first method allows simultaneous estimation of thecontents of hydroxide carbonate and the ldquoborate + boro-hydriderdquo total with their joint presence in the sample Thesecondmethod allows selective determining the borohydridecontent
2 Experimental Section
The contents of hydroxide ions carbonate ions and totalborate and borohydride ions were determined by the acid-base titration method with a 01molsdotLminus1 HCl solution as thetitrant A fuel sample taken from FC for analysis is a highlyalkaline medium For acid-base titration it was repeatedlydiluted A sample of a certain weight (01 to 05 g) wastaken from the fuel analyzed quantitatively transferred toa 250mL glass for titration and brought to 1000mL withdistilled water A homogeneous solution with pH asymp 11ndash13resulted The analysis result was then recalculated in terms
of the initial fuel in view of the dilution factor A fixedinitial volume of the titratable mixture 119881
0
= 1000mL isrequired to further correct modeling of the titration curveTitration was started from some initial pH value and endedat pH asymp 2-3 The positions of peaks were defined and bothtitration curves (integral and differential) were saved in adata file for subsequent computer simulation To analyzeborohydride ions the iodometric redox titration methodwas used The analogous sample of the analyzed fuel (01to 05 g) was quantitatively transferred into a 50mL flaskand brought to the mark with a 1molsdotLminus1 NaOH solutionThen a 5mL aliquot was sampled transferred to a glassfor titration and brought to 50mL with a 1molsdotLminus1 NaOHor KOH solution with further titration with a 01molsdotLminus1standard iodine solution up to a preset potential value Anautomatic ATP-02 titrator (ldquoAquilonrdquo Russia) was appliedThe software package of the titrator provides titration up toa preset electrode potential value or pH at an automaticallychanged rate of the titrant A glass indicator electrode anda silver-chloride reference electrode were used for acid-basetitration a platinum indicator electrode and a glass referenceelectrode were applied for iodometric titration All analyseswere carried out under thermostating at 25∘C
Chemically pure reagents (reagent grade) were used toprepare reference solutions of a desired composition forchecking our analytical methodology The chemicals usedwere NaBO
2
sdot 4H2
O (Vecton Corp Russia the analyticalreagent content 119908NaBO
2
= 0490 plusmn 0003) KBO2
sdot 125H2
O(Vecton Corp the reagent content 119908KBO
2
= 0767 plusmn 0001)NaOH sdot 119909H
2
O (Ecros Corp Russia the reagent content119908NaOH = 0989 plusmn 0002 water content 119908H
2O = 001 plusmn
0003) KOH sdot 119909H2
O (Ecros Corp the reagent content119908KOH = 0898 plusmn 0003 water content 119908H
2O = 0101 plusmn
0003) NaBH4
(Aviabor Corp Russia the reagent content119908NaBH
4
= 0974 plusmn 0005) KBH4
(Aviabor Corp the reagentcontent 119908KBH
4
= 0971 plusmn 0006) and distilled water withoutdissolved carbon dioxide Every reagent had undergone com-mon chemical analysis to analyze the basic substance watercontent and carbonate content No analytically detectablecarbonate impurity in the solid reagents was found Theexact composition of the solid-state reagents was taken intoconsideration at preparing reference solutions The error ofeach controlled concentration of the reference solutions canbe estimated less than 15
3 Results and Discussion
31 Determination of Borohydride Borate Hydroxide andCarbonate by Acid-Based Titration The analyzed object wasan aqueous solution containing a mixture of anions OHminus +BO2
minus
+ BH4
minus
+ CO3
2minus in a random ratio as highly solublesodium and potassium salts During the titration processby an aqueous solution of acid the following reactionsproceed
OHminus +H+ = H2
O (5)
BH4
minus
+ 2H2
O H+997888997888rarr BO
2
minus
+ 4H2
uarr (6)
Journal of Fuels 3
BO2
minus
+H+ = HBO2
(7)
CO3
2minus
+H+ = HCO3
minus (8)
HCO3
minus
+H+ = H2
CO3
(9)
In the presence of BH4
minus the first stage is the irreversiblehydrolysis of BH
4
minus catalyzed with acid which is not con-sumed Protons are consumed at the second stage only(reaction (9)) As a result the total boron (BO
2
minus
+ BH4
minus) istitrated out at the acid-base titration
Reactions (5)ndash(9) proceed concurrently The predomina-tion of this or that reaction is determined by the ratio of thecorresponding dissociation constants of HBO
2
H2
CO3
andwaterH
2
OThis predomination changes as the titration curvegoes with gradual change of pH from the initial pH value asymp11ndash13 to the final one asymp 2-3 The values of the dissociationconstants are such [51 52] that at the addition of acid thefirst reactions (5) and (6) occur then the reactions (7) and (8)proceed and the titration process is completed with reaction(9) It should be noted that the reaction (7) is written ina simplified form as it is known about the existence ofa number of borate anion forms but the final product ofprotolysis is orthoboric acid H
3
BO3
This may be ignoredwithin our pH range
Borohydride hydrolysis reaction (6) takes place in aque-ous alkaline solutions even at high pH but its rate is extremelylow [21] Table 1 comprises approximate rates of BH
4
minus decom-position due to hydrolysis at 25∘C One can see that thehydrolysis of BH
4
minus slowly proceeds at pH asymp 11ndash13 in thesolutions at acid-base titration but this hydrolysis is part ofthe analytical procedure Hydrolysis is sharply acceleratedat pH asymp 7ndash9 and the borate ions formed are further boundin reaction (7) No complex mechanism of the protolysis ofBH4
minus ions [8 21 34] is reflected on the titration curve pHversus 119881
119905
Let us assume that the initial aqueous solution has a
volume 1198810
containing 119899OHminus of alkali 119899BH4
minus of borohydride119899BO2
minus of metaborate and 119899CO3
2minus of carbonate Hydrocar-bonate cannot exist in the initial (highly alkaline) solutionthat is 119899HCO
3
minus = 0 The formation and consumption of verysmall amounts of water during the neutralization reactionare neglected but the dilution degree of the initial mixturetitrant is taken into account The titrant (119905) is an aqueousHCl solution with a concentration 119873
119905
to be added into themixture at the current time in the amount119881
119905
mLThen takinginto account the titrant-caused dilution the overall molarconcentrations 119862
119894
are
119862119905
=119873119905
119881119905
119881 (10)
119862alc =119899OHminus
119881 119862
119861
=119899BH4
minus + 119899BO2
minus
119881 119862carb =
119899CO3
2minus
119881
(11)
Here119881 = 1198810
+119881119905
is the total volume of the mixture at the cur-rent instant of titration Unlike the overall concentrations 119862
119894
the current equilibrium values of the molar concentrations[H+] [OHminus] [BH
4
minus] [BO2
minus] [CO3
2minus] [HCO3
minus] [HBO2
]
Table 1 Approximate rates of borohydride ion BH4
minus decompositiondue to hydrolysis at 25∘C
Concentration [OHminus] or pH Initial rate of BH4
minus decomposition233molsdotLminus1 lt01sdotdayminus1
pH = 13 asymp15sdotdayminus1
pH = 11 asymp7sdothr minus1
pH = 9 asymp02sdotsminus1
pH = 7 gt10sdotsminus1
and [H2
CO3
] are marked with symbols in square bracketsand they are calculated from the equilibrium constants of thetitration reactions
An additional correction is taken into account for theaverage ionic activity coefficient We used the 2nd approxi-mation of Debye-Huckelrsquos theory as Gyuntelbergrsquos equationwhere the activity coefficient is only determined by the ionicstrength of the solution and the squared ion charges [53]Then 119891 is the activity coefficient of all single-charged ionsbut in the equations containing the double-charged carbonateion concentration the factor 1198914 will appear Gyuntelbergrsquosequation at 25∘C looks like
lg119891 = minus05092radic119868
1 + radic119868 (12)
where 119868 = 05sum119894
119888119894
1199112
119894
is the ionic strength of the solutioncalculated by the formula in our case
119868 = 05 times 119862119905
+ 119862alc + 119862119861 + 2 times 119862carb
+ [H+] + [OHminus] + [BH4
minus
] + [BO2
minus
]
+ [HCO3
minus
] + 4 times [CO3
2minus
]
(13)
Gyuntelbergrsquos equation has an advantage over other approx-imations of having no arbitrary parameters and describingwell electrolyte solutions when 119868 asymp 01 which is the casein our acid-base titration (the concentration of any ionsin solution at different stages of titration did not exceed01molsdotLminus1) The concentration of solutions was chosen so asnot to blur steps on the titration curve and at the same timethe correction to the activity coefficients should be small
As a result with the experimental data arrays 119881119905
pH119889pH119889119881
119905
and using (10) and (11) we obtain the data arrays119862119905
119862119861
119862alc and 119862carb The current values of the equilibriumconcentrations at every titration point can be calculated fromthe conditions of chemical equilibrium and material balanceby means of the appropriate formulae
[OHminus] =119870119882
1198912 [H+]
[BH4
minus
] + [BO2
minus
] =119862119861
1 + 1198912 [H+] 119870119861
[CO3
2minus
] =119862carb
1 + (1198914 [H+] 1198702
) (1 + 1198912 [H+] 1198701
)
4 Journal of Fuels
[HCO3
minus
] =119862carb
1 + 1198912 [H+] 1198701
+ 1198702
1198914 [H+]
[H2
CO3
] =119862carb
1 + (1198701
1198912 [H+]) (1 + 1198702
1198914 [H+])
(14)
where
[H+] = 119891minus110minuspH (15)
Here the ionic product of water (autoprotolysis constant)is 119870119882
= 1198912 [OH]sdot[H] = 1 times 10
minus14 at 25∘C [52] thedissociation constant of metaboric acid HBO
2
is 119870B =
1198912
(([BO2
] sdot [H])[HBO2
]) the dissociation constant ofcarbonic acid H
2
CO3
at the first stage is 1198701
= 1198912
(([HCO3
] sdot
[H])[H2
CO3
]) = 445 times 10minus7 at 25∘C [52] the dissociation
constant of carbonic acid H2
CO3
at the second stage is 1198702
=
1198914
(([CO3
] sdot [H])[HCO3
]) = 469 times 10minus11 at 25∘C [52]
Moreover processing the titration curves of simple solutionsof a fixed composition (eg 001molsdotLminus1 NaBO
2
) can be usedfor refinement of these dissociation constants
Let us determine the calculated volume 119881calc of thetitrant from the material balance by acid by boron andby carbon only considering the acid consumption by thetitration reactions (5) (7)ndash(9)Thematerial balance equationis thus written as
119862119905
= [H+] + (119862alc minus [OHminus
])
+ [HBO2
] + [HCO3
minus
] + 2 times [H2
CO3
] (16)
(the initial content of acid in an alkaline solution [H+]0 lt10minus11molsdotLminus1 is ignored)The calculated value of119881calc is estimated from the current
pH value and (10) and (15) As a result the calculated pointsof the titration curve of solutions containing a mixture ofanions OHminus BH
4
minus BO2
minus and CO3
2minus are determined by theequation
119881calc =119881
119873HCl([H+] + Calc minus [OH
minus
] + 119862119861
minus [BH4
minus
]
minus [BO2
minus
] + [HCO3
minus
] + 2 times [H2
CO3
])
(17)
where the current equilibrium values ofmolar concentrationsare determined by (14) and (15) Equation (17) is veryconvenient for computer simulations It allows calculatingthe pH minus 119881calc dependence and plotting the whole calculatedtitration curve By means of fitting the calculated curve to theexperimental curve we find the amounts of components inthe sample 119899OHminus 119899BH
4
minus+BO2
minus and 119899CO3
2minus The concentrationof borate is calculated by the difference of total boron minusborohydride that is 119899BO
2
minus = 119899BH4
minus+BO2
minus minus 119899BH4
minus The amountof borohydride in the mixture is selectively determined byiodometric titration
32 Determination of Borohydride in Solution by IodometricTitration As shown in [39] the quantification of BH
4
minus
in solution by direct iodometric titration is based on thereaction proceeding quantitatively in an alkaline medium
4I2
+ BH4
minus
+ 8OHminus = BO2
minus
+ 8Iminus + 6H2
O (18)
Usually the direct titration is made in a low alkaline medium(pH lt 11) because iodine interacts with hydroxide ions toform nonactive iodate ion IO
3
minus in higher alkaline solution[34]
3I2
+ 6OHminus 997888rarr IO3
minus
+ 5Iminus + 3H2
O (19)
However borohydride ions are insufficiently stable atroom temperature when pH lt 11 Table 1 comprises approx-imate rates of BH
4
minus decomposition due to hydrolysis Onecan see that the fuel with alkalinity above 2molsdotLminus1 is almostnot subjected to hydrolysis at 25∘C The same applies to theiodometric redox titrationmethod used by us which requiresa 1molsdotLminus1 NaOH solution In a 1molsdotLminus1 alkaline solutionthe addition of iodine to borohydride is also accompanied byextremely slight hydrogen release as a result of borohydridedecomposition Under these conditions about 05ndash1 ofBH4
minus ions is decomposed while a negligible amount ofiodate is formed by reaction (18) with iodine consumptionof sim05ndash1 Thus any mistakes are compensated and directiodometric titration allows one to obtain the result closest tothe true value of borohydride concentration (the error not toexceed 005)
33 Processing Titration Curves and Estimation of AccuracyThe titration curves pH versus119881
119905
and the appropriate depen-dences 119889pH119889119881
119905
versus 119881119905
obtained by acid-base titration ofaqueous solutions of various anion mixtures are shown inFigure 1 and the analogous curves obtained by iodometrictitration are shown in Figure 2 The first distinct step pre-sented (not always) on the iodometric titration curve reflectsa complex mechanism of the chemical reaction (18) and isneglected The determination of the amount of the titrantis carried out by the second sharp leap within the potentialrange 0 to 600mV (Figure 2)
The titration curves were processed by two ways namelya simple method of differentiation and a more complexmethod of computer simulations For the iodometric deter-mination of borohydride it is enough to use the method ofdifferentiation only while for acid-base titration the bestresults are obtained when both methods (differentiation andsimulation) are used
Themethod of differentiation is based on the equivalencepoints coinciding with the inflections on the pH versus119881119905
curve and with appropriate maxima on the differential119889pH119889119881
119905
versus 119881119905
curve (Figure 1) The positions of themaximum points 119881lowast
119905
are fixed the titrant volume consumedfor titration of the 119894th component Δ119881lowast
119905
= 119881lowast
119905119894
minus 119881lowast
119905119894minus1
ismeasured and the amount of each component is calculatedHowever in few complex cases it is possible to state thatan extreme point on the differential 1198892pH119889(119881
119905
)2 = 0 curve
is close to an equivalence point at sharp changes of pH Ifsmoothed inflections with a small pH difference are observedor two points of inflection are near each other a significantsystematic error arises
The method of simulation is based on the theoryexplained aboveThe program for calculating titration curvesuses the appropriate theoretical equations (10)ndash(17) and com-bines the experimental pH versus119881
119905
curvewith the calculated
Journal of Fuels 5
0
2
4
6
8
10
12
14
0 4 8 12
pH
ExperimentCalculationDifferentiation
Vt (mL)
minus100
900
1900
2900
3900
4900
dpH
dVt
OH minus
(a)
0
20
40
60
80
100
120
0
2
4
6
8
10
12
14
0 2 4 6 8 10 12 14
pH
ExperimentCalculationDifferentiation
Vt (mL)
dpH
dVt
OHminus+ CO3
2minus
(b)
0
20
40
60
80
100
120
0
4
8
12
16
0 1 2 3 4 5 6
pH
ExperimentCalculationDifferentiation
Vt (mL)
dpH
dVt
OHminus+ BH4
minus+ BO2
minus
(c)
20
0
40
60
80
100
120
0
2
4
6
8
10
12
14
0 2 4 6 8
pH
ExperimentCalculationDifferentiation
Vt (mL)
dpH
dVt
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
(d)
Figure 1 Calculated titration curves experimental titration curves and the corresponding 119889pH119889119881119905
versus 119881119905
curves for aqueous solutionsof several mixtures of anions (a) OHminus (b) OHminus + CO
3
2minus (c) OHminus + BH4
minus or OHminus + BO2
minus or OHminus + BH4
minus
+ BO2
minus (d) OHminus + BH4
minus
+
BO2
minus
+ CO3
minus
pH versus 119881calc one The variable parameters are the soughtquantities of components in the aliquot 119899OHminus 119899BH
4
minus+BO2
minus and119899CO3
2minus The criterion of optimum is the minimum dispersion
1198782
=sum119870
119896=1
(pH119896
minus pHcalc119896)2
119870 minus 1
=sum119870
119896=1
((119889pH119889119881119905119896
) (119881119905119896
minus 119881calc119896))2
119870 minus 1
(20)
Here119870 is the number of points on the titration curve Figure 1shows the experimental and calculated titration curves forfew solutions of various multicomponent mixtures It is
visible that the applied computational methods allow exactsimulating experimental curves
Error Analysis and Estimation of AccuracyAnumber of refer-ence solutions of a desired composition were prepared usingKBO2
NaBH4
KBH4
NaOHKOHNa2
CO3
andK2
CO3
forvalidation of our analytical methodology (the concentrationranges of each analyzed ion in the considered samples arepresented in Table 2) In order to detect systematic errorsthe dependences of the ldquomeasuredweightedrdquo ratios on theanionic fraction 120596
119894
were plotted (120596119894
is the mole fraction ofthe 119894th anion in the total amount of the analyzed anions 120596varies from 0 up to 1) The results are given in Figure 3 Theaverage value of the ldquomeasuredweightedrdquo ratio for each ionis presented in Table 3
6 Journal of Fuels
Table 2 Considered concentration ranges of analyzed ions in thesample
Ion Concentration range in the analyzed sample molsdotLminus1
OHminus 002ndash12BH4
minus 002ndash02BO2
minus 005ndash02CO3
2minus 0008ndash01
It is apparent from Table 3 that the simulation methodalso gives a systematic error The causes can be simplificationof the theory the impossibility to consider all side processesthe inability to exactly calculate activity coefficients and soforth so the shape of the calculated curve may not com-pletely coincide with the experimental curve In particularin the titration process of borate solutions the formationof poliborates and their hydrated forms is possible In thecase of simulation the lower branch of the titration curveshould be limitedwhen all equivalence points are passed overAccelerated titration or cold solutionmay cause an additionalerror due to the inhibition of reaction (6) and the failure ofchemical equilibrium
The concentration of OHminus ions is estimated with an accu-racy of 0959 and 0956 for the differentiation and simulationmethods respectivelyThe total of (BH
4
minus
+BO2
minus) is estimatedwith an accuracy of 1023 and 1012 for the differentiationand simulation methods respectively (Table 3) Thus for theOHminus+BH
4
minus
+BO2
minus system the differentiation and simulationmethods give similar results and have no advantages overeach other and the systematic error is small but naturallyincreases with decreasing share of the analyzed ionThe trendof the systematic error is shown in Figure 3(a) by means ofsolid lines Both methods overestimate the content of boronin the sample and underestimate the content of alkali Forcompensation of the systematic error the following equationshave been obtained for the method of differentiation
120573OHminus = [138 minus 04120596minus005
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [120596minus005
BH4
minus+BO2
minus minus 0025]minus1
(21)
and for the method of simulation
120573OHminus = [139 minus 04120596minus008
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [07120596minus005
BH4
minus+BO2
minus + 028]minus1
(22)
After analysis and the determination of the components119899OHminus and 119899BH
4
minus+BO2
minus a correction procedure was carried outby multiplying the values 119899
119894
found by the correspondingcorrection coefficients 120573
119894
calculated from formulae (21) or(22) Finally the corrected amounts of the 119894th component inthe sample 119899
119894cor are
119899119894cor = 120573119894119899119894 (23)
Figure 3(b) shows the result of correction of the data given inFigure 3(a)The systematic error was totally compensated forall the variants of analysis (Table 3)
0 2 4 6 8 10Vt (mL)
minus600
minus200
200
600
1000
E(m
V)
Vlowastt
minus27000
minus18000
minus9000
0
9000
dEdVt
Figure 2 Curve of direct iodometric titration of borohydride ionsin an aqueous solution with the mixture of anions OHminus + BH
4
minus
+
BO2
minus
+ CO3
2minus (119881lowast119905
is equivalence point)
When the value of the anionic fraction 04 lt 120596119894
lt 1 allpoints lie within the ldquomeasuredweightedrdquo range 095ndash105that is the random error does not exceed 5 all points liewithin the range 088ndash112 when 005 lt 120596
119894
lt 04 that isthe random error does not exceed 12 It is only possibleto perform semiquantitative analysis of any component at itsvery small content in the mixture (120596
119894
lt 002) On correctionthe average accuracy parameter of the OHminus concentrationis 1000 for differentiation and 1001 for simulation and theaverage accuracy parameter for the (BH
4
minus
+ BO2
minus
) total is1008 for differentiation and 1004 for simulation (Table 3)
The feature of titration of alkaline-carbonate solutionsis the existence of three leaps on the titration curve(Figure 1(b))The first leap belongs to alkali while the secondand third ones are due to carbonates Correspondingly whenthe quantities of components are determined by the locationof peaks on the differential curve the quantity of CO
3
2minus isincluded twiceThe analysis of carbonate bymeans of the sec-ond peak gives a worse result than by the third one At a verysmall content of carbonate the second peak is not detectedThe average ldquomeasuredweightedrdquo value is 1215 for CO
3
2minus
ions by the second peak on the differential curve and 1115in the case of the third peak and the ldquomeasuredweightedrdquovalue is 1089 for the method of simulation The results ofcontrol determination of the alkali and carbonate contents inthe reference solutions OHminus + CO
3
2minus are shown in Figures3(c) and 3(d) for the two methods as the dependence ofthe accuracy parameter on the anionic fractions 120596
119894
In allcases the points of differentiation are more distant fromthe ldquocorrectrdquo level than those of simulation Consequentlythe method of simulation gives more correct results for theOHminus + CO
3
2minus system while the method of determinationcannot be recommended because of its high systematic errorsin carbonate analysis
The systematic error naturally increases with decreasingfractions of the analyzed ions In Figure 3(c) the trend ofsystematic errors is shown by means of solid lines for the
Journal of Fuels 7
Table 3 Average values of the ldquomeasuredweightedrdquo ratios for each ion in the mixture before and after correction of systematic errors
System Ions Method ldquoMeasuredweightedrdquo ratioBefore correction After correction
OHminus + BH4
minus + BO2
minus
OHminus Differentiation 0959 1000Simulation 0956 1001
BH4
minus + BO2
minus
Differentiation 1023 1008Simulation 1012 1004
OHminus + CO3
2minus
OHminus Simulation 0985 1003CO3
2minus Simulation 1089 0996
OHminus + BH4
minus + BO2
minus + CO3
2minus
OHminus Simulation 0874 0958BH4
minus + BO2
minus Simulation 1040 0992CO3
2minus Simulation 0934 1008
08
09
1
11
12
13
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ BH4
minus+ BO2
minus
OHminus simulationBH4
minus+ BO2
minus simulationNormOHminus differentiationBH4
minus+ BO2
minus differentiation
(a)
08
09
1
11
12
13
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ BH4
minus+ BO2
minus
OHminus simulationBH4
minus+ BO2
minus simulation + correctionNormOHminus differentiation + correctionBH4
minus+ BO2
minus differentiation + correction
(b)
05060708091
1112131415
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ CO3
2minus
OHminus simulation
NormCO3
2minus simulation
(c)
07
08
09
1
11
12
13
14
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ CO3
2minus
simulation + correctionOHminus
Normsimulation + correctionCO3
2minus
(d)
0
02
04
06
08
1
12
14
0 02 04 06 08 1
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
OHminus simulationBH4
minus+ BO2
minus simulationNormOHminus differentiation
CO32minus simulation
CO32minus differentiation
120596i
Measuredweighted
BH4minus+ BO2
minus+ CO3
2minus differentiation
(e)
Measuredweighted
02
04
06
08
1
12
14
0 02 04 06 08 1120596i
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
BH4minus+ BO2
minus simulation + correctionOHminus simulation + correction
Normsimulation + correctionCO3
2minus
(f)
Figure 3 Dependence of the ldquomeasuredweightedrdquo ratios for anions on their mole fraction 120596119894
in the mixture (a) for the OHminus + BH4
minus
+
BO2
minus system before correction of systematic errors (b) for the OHminus + BH4
minus
+ BO2
minus system after correction of systematic errors (c) for theOHminus +CO
3
2minus system before correction of systematic errors (d) for the OHminus +CO3
2minus system after correction of systematic errors (e) for theOHminus + BH
4
minus
+ BO2
minus
+CO3
2minus system before correction of systematic errors (f) for the OHminus + BH4
minus
+ BO2
minus
+CO3
2minus system after correctionof systematic errors The solid lines show the average trend of errors The dotted lines show the error interval for the method of simulation
8 Journal of Fuels
method of simulation The following equations have beensuggested for compensation of this trend
120573OHminus = [29 minus 19120596minus0055
OHminus ]minus1
120573CO3
2minus = [75120596minus001
CO3
2minus minus 65]minus1
(24)
After analysis and the determination of the 119899OHminus and 119899CO3
2minus
values a correction procedure is carried out by formula(24) Figure 3(d) shows the result of such correction Thesystematic error is completely compensated (Table 3) Allpoints lie within the ldquomeasuredweightedrdquo range 095ndash105for the anionic fractions within 04 lt 120596
119894
lt 1 that is therandom error does not exceed 5 and the random scatteringdoes not exceed 12 when 015 lt 120596
119894
lt 04 If the fractionof carbonate is less than 015 the reliability of its analysisdecreases because of the high random dispersion thereforeit is required to increase the number of replicate samplesThedirect titrimetric analysis of carbonate becomes impossiblewhen 120596CO
3
2minus lt 0015A feature of titration of alkaline-borohydride-borate-
carbonate solutions is the existence of three weak leaps onthe titration curve (Figure 1(d)) The first leap belongs toalkali while the second belongs to the ldquoBH
4
minus
+ BO2
minus
+
CO3
2minusrdquo total and the third one belongs to carbonate ionsRespectively at the quantification of components by meansof the position of peaks on the differential curve the totalcontent of boron 119899BH
4
minus+BO2
minus can be only calculated after thedetermination and extraction of the carbonate quantity
The results of our control determination of the anioncontents in the OHminus + BH
4
minus
+ BO2
minus
+ CO3
2minus mixturesby both methods are shown in Figure 3(e) The methodof differentiation gives an unsatisfactory result for car-bonate underestimating its content significantly the meanldquomeasuredweightedrdquo value being 0615 The carbonate peakdisappears when 120596CO
3
2minus lt 015 which leads to incorrectdetermination of the BH
4
minus
+ BO2
minus total Therefore for theOHminus+ BH
4
minus
+ BO2
minus
+ CO3
2minus system (the highly carbonatedand discharged fuel) the method of differentiation cannotbe recommended because of its large systematic errors incarbonate analysis and the method of simulation is onlysuggested for use The mean ldquomeasuredweightedrdquo values areshown in Table 3 The determination accuracy is 0874 forOHminus ions 1040 for the BH
4
minus
+ BO2
minus total and 0934 forCO3
2minus ions After correction these parameters become 09580992 and 1008 respectively The correcting coefficients are
120573OHminus = [198 minus 120596minus005
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [120596minus0085
BH4
minus+BO2
minus minus 003]minus1
120573CO3
2minus = [195 minus 120596minus001
CO3
2minus]minus1
(25)
The systematic error is thus compensated however therandom scattering of the points is higher than with moresimple options The random dispersion for alkali and borondoes not exceed 15 (all points arewithin 085ndash115) howeverit is only fair for carbonatewhen120596CO
3
2minus gt 01 If the carbonate
content is less than 01 its semiquantitative analysis is onlypossible But very small amounts of carbonate will not affectthe functioning of DBFC and only higher concentrations ofcarbonate exceeding the solubility limit can be deposited inthe electrode to hinder the functioning of DBFC
4 Conclusions
Theanalytic technique presented in our paper includes takinga small fuel sample from DBFC and performing two types oftitrations (acid-base and iodometric ones) which supplementeach otherThenecessity of exactly two techniques of titrationis due to the fact that iodometric titration determines theBH4
minus quantity in the sample only while the quantities ofother fuel components are provided by acid-base titration(OHminus BO
2
minus CO3
2minus)Therefore the joint application of thesetitration techniques allows one to most fully quantify thecurrent state of fuel in the process of DBFC functioningThe determination correctness of the technique has beenshown on artificial mixtures with a wide variation of theircomposition The average error depends on the number ofcomponents and their ratio in the mixture The investigationresults show that in the most complex case of highly carbon-ated and discharged fuel the maximal error of determinationdoes not exceed 15
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgment
The authors would like to gratefully acknowledge the RussianFoundation for Basic Research for financial support (Projectno 12-03-31802)
References
[1] J B Lakeman A Rose K D Pointon et al ldquoThe directborohydride fuel cell for UUV propulsion powerrdquo Journal ofPower Sources vol 162 no 2 pp 765ndash772 2006
[2] C P de Leon F C Walsh D Pletcher D J Browning and JB Lakeman ldquoDirect borohydride fuel cellsrdquo Journal of PowerSources vol 155 no 2 pp 172ndash181 2006
[3] R Aiello J H Sharp and M A Matthews ldquoProduction ofhydrogen from chemical hydrides via hydrolysis with steamrdquoInternational Journal of Hydrogen Energy vol 24 no 12 pp1123ndash1130 1999
[4] S C Amendola S L Sharp-Goldman M S Janjua et al ldquoSafeportable hydrogen gas generator using aqueous borohydridesolution and Ru catalystrdquo International Journal of HydrogenEnergy vol 25 no 10 pp 969ndash975 2000
[5] H I Schlesinger H C Brown A E Finholt J R GilbreathH R Hoekstra and E K Hyde ldquoSodium borohydride itshydrolysis and its use as a reducing agent and in the generationof hydrogenrdquo Journal of the American Chemical Society vol 75no 1 pp 215ndash219 1953
Journal of Fuels 9
[6] S C Amendola P Onnerud M T Kelly P J Petillo S LSharp-Goldman and M Binder ldquoNovel high power densityborohydride-air cellrdquo Journal of Power Sources vol 84 no 1 pp130ndash133 1999
[7] B H Liu and Z P Li ldquoCurrent status and progress of directborohydride fuel cell technology developmentrdquo Journal ofPower Sources vol 187 no 2 pp 291ndash297 2009
[8] B H Liu and Z P Li ldquoA review hydrogen generation fromborohydride hydrolysis reactionrdquo Journal of Power Sources vol187 no 2 pp 527ndash534 2009
[9] B Weng Z Wu Z Li H Yang and H Leng ldquoHydrogengeneration from noncatalytic hydrolysis of LiBH4NH3BH3mixture for fuel cell applicationsrdquo International Journal ofHydrogen Energy vol 36 no 17 pp 10870ndash10876 2011
[10] A E Sanli I Kayacan B Z Uysal and M L Aksu ldquoRecoveryof borohydride from metaborate solution using a silver catalystfor application of direct rechargable borohydrideperoxide fuelcellsrdquo Journal of Power Sources vol 195 no 9 pp 2604ndash26072010
[11] R Jamard J Salomon A Martinent-Beaumont and CCoutanceau ldquoLife time test in direct borohydride fuel cellsystemrdquo Journal of Power Sources vol 193 no 2 pp 779ndash7872009
[12] J-H Wee ldquoA comparison of sodium borohydride as a fuel forproton exchange membrane fuel cells and for direct borohy-dride fuel cellsrdquo Journal of Power Sources vol 155 no 2 pp329ndash339 2006
[13] A V Churikov K V Zapsis V V Khramkov M A ChurikovM P Smotrov and I A Kazarinov ldquoPhase diagrams of theternary systems NaBH
4
+ NaOH + H2
O KBH4
+ KOH + H2
ONaBO
2
+ NaOH + H2
O and KBO2
+ KOH + H2
O at minus10∘CrdquoJournal of Chemical and Engineering Data vol 56 no 1 pp 9ndash13 2011
[14] A V Churikov K V Zapsis V V Khramkov M A Churikovand I M Gamayunova ldquoTemperature-induced transformationof the phase diagrams of ternary systems NaBO
2
+ NaOH+ H2
O and KBO2
+ KOH + H2
Ordquo Journal of Chemical andEngineering Data vol 56 no 3 pp 383ndash389 2011
[15] A V Churikov K V Zapsis A V Ivanishchev and V OSychova ldquoTemperature-induced transformation of the phasediagrams of ternary systems NaBH
4
+ NaOH +H2
O and KBH4
+ KOH + H2
Ordquo Journal of Chemical and Engineering Data vol56 no 5 pp 2543ndash2552 2011
[16] G Rostamikiaa and M J Janik ldquoDirect borohydride oxidationmechanism determination and design of alloy catalysts guidedby density functional theoryrdquo Energy amp Environmental Sciencevol 3 pp 1262ndash1274 2010
[17] B Sljuki J Miliki D M F Santosa and C A C SequeiraldquoCarbon-supported Pt
075
M025
(M = Ni or Co) electrocatalystsfor borohydride oxidationrdquo Electrochim Acta vol 107 pp 577ndash583 2013
[18] B H Liu J Q Yang and Z P Li ldquoConcentration ratio of[OHminus][BH
4
minus] a controlling factor for the fuel efficiency ofborohydride electro-oxidationrdquo International Journal of Hydro-gen Energy vol 34 no 23 pp 9436ndash9443 2009
[19] A V Churikov A V Ivanishchev I M Gamayunova andA V Ushakov ldquoDensity calculations for (Na K)BH
4
+ (NaK)BO
2
+ (Na K)OH + H2
O solutions used in hydrogen powerengineeringrdquo Journal of Chemical and Engineering Data vol 56no 11 pp 3984ndash3993 2011
[20] A V Churikov V O Romanova M A Churikov and I MGamayunova ldquoThemodel of fuel transformation at discharge of
direct borohydride fuel cellrdquo International Review of ChemicalEngineering vol 4 pp 263ndash268 2012
[21] A V Churikov I M Gamayunova K V Zapsis M AChurikov and A V Ivanishchev ldquoInfluence of temperature andalkalinity on the hydrolysis rate of borohydride ions in aqueoussolutionrdquo International Journal of Hydrogen Energy vol 37 no1 pp 335ndash344 2012
[22] Z P Li B H Liu K Arai and S Suda ldquoA fuel cell developmentfor using borohydrides as the fuelrdquo Journal of the Electrochemi-cal Society vol 150 no 7 pp A868ndashA872 2003
[23] Y Wang P Hea and H Zhou ldquoA novel direct borohydridefuel cell using an acid-alkaline hybrid electrolyterdquo Energy ampEnvironmental Science vol 3 no 10 pp 1515ndash1518 2010
[24] J Ma N A Choudhury and Y Sahai ldquoA comprehensive reviewof direct borohydride fuel cellsrdquo Renewable and SustainableEnergy Reviews vol 14 no 1 pp 183ndash199 2010
[25] R Bruhlmann and L Piatti ldquoAn improved method for thetitrimetric determination of boron in ironrdquo Chimia vol 11 p203 1957
[26] A Keshan and C Bimba ldquoCobalt-potassium and ammonium-cobalt dodecaboraterdquo Izvestiya Akademii Nauk Latvijskoj SSRp 115 1954
[27] J Czakow T Steciak and O Szczebinska ldquoThe spectral deter-mination of trace amounts of impurities in the solutions withthe metal electrodes in the spark moderdquo Analytical Chemistryvol 3 p 745 1958
[28] R Rosotti ldquoA fast method for the determination of traceamounts of boron in the steelrdquo Analytical Chemistry vol 44 p208 1962
[29] J Varka and A Sklaf ldquoApplication of potentiometric titrationIV Determination of B
2
O3
in glass enamels and boron-containing raw materialsrdquo Keramik vol 7 p 12 1957
[30] D E Williams and J Vilamis ldquoStability of the curcumincomplex in boron determinationrdquoAnalytical Chemistry vol 33pp 1098ndash1100 1961
[31] S Kertes and M Lederer ldquoPaper chromatography of inorganicions Rf values in mixtures of butanol and Hbrrdquo AnalyticaChimica Acta vol 15 no C pp 543ndash547 1956
[32] A A Nemodruk and Z K Karalova The Analytical Chemistryof Boron Nauka 1964
[33] C A Parker ldquoRaman spectra in spectrofluorimetryrdquo The Ana-lyst vol 84 no 1000 pp 446ndash453 1959
[34] C A Parker and W J Barnes ldquoFluorimetric determination ofboron application to silicon sea water and steelrdquo The Analystvol 85 no 1016 pp 828ndash838 1960
[35] M V Akhmanova Methods of Determination and Analysis ofRear Elements Izdat Akademija Nauk SSSR 1961
[36] E H Jensen A Study on Sodium Borohydride Nyt NordiskForlag Amold Busck Copenhagen Denmark 1954
[37] I Fatt and M Tashima Alkali Metal Dispersions D VanNostrand Co Inc Princeton NJ USA 1961
[38] DA Lyttle EH Jensen andWA Struck ldquoA simple volumetricassay for sodium borohydriderdquo Analytical Chemistry vol 24no 11 pp 1843ndash1844 1952
[39] P K Norkus ldquoIodometric determination of borohydriderdquoRussian Journal of Analytical Chemistry vol 23 pp 908ndash9111968
[40] N N Malrsquoceva and V S Khain Sodium Borohydride Propertiesand Application Nauka 1985
10 Journal of Fuels
[41] C Harzdorf and O Steinhauser ldquoZur photometrisehen Titra-tion von Fluorid mit Thoriumnitratrdquo Freseniusrsquo Zeitschrift furAnalytische Chemie vol 210 no 2 pp 106ndash112 1965
[42] W D Davis L S Mason and G Stegeman ldquoThe heats offormation of sodium borohydride lithium borohydride andlithium aluminum hydriderdquo Journal of the American ChemicalSociety vol 71 no 8 pp 2775ndash2781 1949
[43] S W Chaikin ldquoDirect volumetric assay of sodium borohydrideand potassium borohydriderdquo Analytical Chemistry vol 25 no5 pp 831ndash832 1953
[44] U Ulku and G Somer ldquoDetermination of trace borohydride inbasic solutions using differential pulse polarographyrdquo TurkishJournal of Chemistry vol 33 pp 657ndash665 2009
[45] H Celikkan H Aydin and M L Aksu ldquoThe electroanalyticaldetermination of sodium borohydride using a gold electroderdquoTurkish Journal of Chemistry vol 29 pp 519ndash524 2005
[46] M V Mirkin and A J Bard ldquoVoltammetric method forthe determination of borohydride concentration in alkalineaqueous solutionsrdquoAnalytical Chemistry vol 63 no 5 pp 532ndash533 1991
[47] D M F Santos and C A C Sequeira ldquoPotentiometric moni-toring of sodium borohydride in aqueous solutionsrdquo Ciencia sTecnologia dos Materials vol 20 no 3-4 pp 31ndash34 2008
[48] D M F Santos and C A C Sequeira ldquoSodium borohydridedetermination by measurement of open circuit potentialsrdquoJournal of Electroanalytical Chemistry vol 627 pp 1ndash8 2009
[49] H C Brown and A C Boyd Jr ldquoArgentimetric procedure forborohydride determinationrdquo Analytical Chemistry vol 27 no1 pp 156ndash158 1955
[50] V B Breicis A O Berzina and L K Lepin ldquoPotentiomet-ric titration of water solutions of sodium borohydride byhydrochloric acidrdquo Scientific Short Letter of Riga PolytechnicInstitute vol 15 pp 179ndash188 19651966
[51] U U Lurie Handbook on Analytical Chemistry Khimiya 1979[52] R A Lidin L L Andreeva and V A Molochko Hand-
book of Inorganic Chemistry Constants of Inorganic SubstancesKhimiya 1987
[53] R A Robinson and R H Stokes Electrolyte Solutions the Mea-surement and Interpretation of Conductance Chemical Potentialand Diffusion in Solutions of Simple Electrolytes ButterworthsLondon UK 1959
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Renewable Energy
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High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Journal of Fuels 3
BO2
minus
+H+ = HBO2
(7)
CO3
2minus
+H+ = HCO3
minus (8)
HCO3
minus
+H+ = H2
CO3
(9)
In the presence of BH4
minus the first stage is the irreversiblehydrolysis of BH
4
minus catalyzed with acid which is not con-sumed Protons are consumed at the second stage only(reaction (9)) As a result the total boron (BO
2
minus
+ BH4
minus) istitrated out at the acid-base titration
Reactions (5)ndash(9) proceed concurrently The predomina-tion of this or that reaction is determined by the ratio of thecorresponding dissociation constants of HBO
2
H2
CO3
andwaterH
2
OThis predomination changes as the titration curvegoes with gradual change of pH from the initial pH value asymp11ndash13 to the final one asymp 2-3 The values of the dissociationconstants are such [51 52] that at the addition of acid thefirst reactions (5) and (6) occur then the reactions (7) and (8)proceed and the titration process is completed with reaction(9) It should be noted that the reaction (7) is written ina simplified form as it is known about the existence ofa number of borate anion forms but the final product ofprotolysis is orthoboric acid H
3
BO3
This may be ignoredwithin our pH range
Borohydride hydrolysis reaction (6) takes place in aque-ous alkaline solutions even at high pH but its rate is extremelylow [21] Table 1 comprises approximate rates of BH
4
minus decom-position due to hydrolysis at 25∘C One can see that thehydrolysis of BH
4
minus slowly proceeds at pH asymp 11ndash13 in thesolutions at acid-base titration but this hydrolysis is part ofthe analytical procedure Hydrolysis is sharply acceleratedat pH asymp 7ndash9 and the borate ions formed are further boundin reaction (7) No complex mechanism of the protolysis ofBH4
minus ions [8 21 34] is reflected on the titration curve pHversus 119881
119905
Let us assume that the initial aqueous solution has a
volume 1198810
containing 119899OHminus of alkali 119899BH4
minus of borohydride119899BO2
minus of metaborate and 119899CO3
2minus of carbonate Hydrocar-bonate cannot exist in the initial (highly alkaline) solutionthat is 119899HCO
3
minus = 0 The formation and consumption of verysmall amounts of water during the neutralization reactionare neglected but the dilution degree of the initial mixturetitrant is taken into account The titrant (119905) is an aqueousHCl solution with a concentration 119873
119905
to be added into themixture at the current time in the amount119881
119905
mLThen takinginto account the titrant-caused dilution the overall molarconcentrations 119862
119894
are
119862119905
=119873119905
119881119905
119881 (10)
119862alc =119899OHminus
119881 119862
119861
=119899BH4
minus + 119899BO2
minus
119881 119862carb =
119899CO3
2minus
119881
(11)
Here119881 = 1198810
+119881119905
is the total volume of the mixture at the cur-rent instant of titration Unlike the overall concentrations 119862
119894
the current equilibrium values of the molar concentrations[H+] [OHminus] [BH
4
minus] [BO2
minus] [CO3
2minus] [HCO3
minus] [HBO2
]
Table 1 Approximate rates of borohydride ion BH4
minus decompositiondue to hydrolysis at 25∘C
Concentration [OHminus] or pH Initial rate of BH4
minus decomposition233molsdotLminus1 lt01sdotdayminus1
pH = 13 asymp15sdotdayminus1
pH = 11 asymp7sdothr minus1
pH = 9 asymp02sdotsminus1
pH = 7 gt10sdotsminus1
and [H2
CO3
] are marked with symbols in square bracketsand they are calculated from the equilibrium constants of thetitration reactions
An additional correction is taken into account for theaverage ionic activity coefficient We used the 2nd approxi-mation of Debye-Huckelrsquos theory as Gyuntelbergrsquos equationwhere the activity coefficient is only determined by the ionicstrength of the solution and the squared ion charges [53]Then 119891 is the activity coefficient of all single-charged ionsbut in the equations containing the double-charged carbonateion concentration the factor 1198914 will appear Gyuntelbergrsquosequation at 25∘C looks like
lg119891 = minus05092radic119868
1 + radic119868 (12)
where 119868 = 05sum119894
119888119894
1199112
119894
is the ionic strength of the solutioncalculated by the formula in our case
119868 = 05 times 119862119905
+ 119862alc + 119862119861 + 2 times 119862carb
+ [H+] + [OHminus] + [BH4
minus
] + [BO2
minus
]
+ [HCO3
minus
] + 4 times [CO3
2minus
]
(13)
Gyuntelbergrsquos equation has an advantage over other approx-imations of having no arbitrary parameters and describingwell electrolyte solutions when 119868 asymp 01 which is the casein our acid-base titration (the concentration of any ionsin solution at different stages of titration did not exceed01molsdotLminus1) The concentration of solutions was chosen so asnot to blur steps on the titration curve and at the same timethe correction to the activity coefficients should be small
As a result with the experimental data arrays 119881119905
pH119889pH119889119881
119905
and using (10) and (11) we obtain the data arrays119862119905
119862119861
119862alc and 119862carb The current values of the equilibriumconcentrations at every titration point can be calculated fromthe conditions of chemical equilibrium and material balanceby means of the appropriate formulae
[OHminus] =119870119882
1198912 [H+]
[BH4
minus
] + [BO2
minus
] =119862119861
1 + 1198912 [H+] 119870119861
[CO3
2minus
] =119862carb
1 + (1198914 [H+] 1198702
) (1 + 1198912 [H+] 1198701
)
4 Journal of Fuels
[HCO3
minus
] =119862carb
1 + 1198912 [H+] 1198701
+ 1198702
1198914 [H+]
[H2
CO3
] =119862carb
1 + (1198701
1198912 [H+]) (1 + 1198702
1198914 [H+])
(14)
where
[H+] = 119891minus110minuspH (15)
Here the ionic product of water (autoprotolysis constant)is 119870119882
= 1198912 [OH]sdot[H] = 1 times 10
minus14 at 25∘C [52] thedissociation constant of metaboric acid HBO
2
is 119870B =
1198912
(([BO2
] sdot [H])[HBO2
]) the dissociation constant ofcarbonic acid H
2
CO3
at the first stage is 1198701
= 1198912
(([HCO3
] sdot
[H])[H2
CO3
]) = 445 times 10minus7 at 25∘C [52] the dissociation
constant of carbonic acid H2
CO3
at the second stage is 1198702
=
1198914
(([CO3
] sdot [H])[HCO3
]) = 469 times 10minus11 at 25∘C [52]
Moreover processing the titration curves of simple solutionsof a fixed composition (eg 001molsdotLminus1 NaBO
2
) can be usedfor refinement of these dissociation constants
Let us determine the calculated volume 119881calc of thetitrant from the material balance by acid by boron andby carbon only considering the acid consumption by thetitration reactions (5) (7)ndash(9)Thematerial balance equationis thus written as
119862119905
= [H+] + (119862alc minus [OHminus
])
+ [HBO2
] + [HCO3
minus
] + 2 times [H2
CO3
] (16)
(the initial content of acid in an alkaline solution [H+]0 lt10minus11molsdotLminus1 is ignored)The calculated value of119881calc is estimated from the current
pH value and (10) and (15) As a result the calculated pointsof the titration curve of solutions containing a mixture ofanions OHminus BH
4
minus BO2
minus and CO3
2minus are determined by theequation
119881calc =119881
119873HCl([H+] + Calc minus [OH
minus
] + 119862119861
minus [BH4
minus
]
minus [BO2
minus
] + [HCO3
minus
] + 2 times [H2
CO3
])
(17)
where the current equilibrium values ofmolar concentrationsare determined by (14) and (15) Equation (17) is veryconvenient for computer simulations It allows calculatingthe pH minus 119881calc dependence and plotting the whole calculatedtitration curve By means of fitting the calculated curve to theexperimental curve we find the amounts of components inthe sample 119899OHminus 119899BH
4
minus+BO2
minus and 119899CO3
2minus The concentrationof borate is calculated by the difference of total boron minusborohydride that is 119899BO
2
minus = 119899BH4
minus+BO2
minus minus 119899BH4
minus The amountof borohydride in the mixture is selectively determined byiodometric titration
32 Determination of Borohydride in Solution by IodometricTitration As shown in [39] the quantification of BH
4
minus
in solution by direct iodometric titration is based on thereaction proceeding quantitatively in an alkaline medium
4I2
+ BH4
minus
+ 8OHminus = BO2
minus
+ 8Iminus + 6H2
O (18)
Usually the direct titration is made in a low alkaline medium(pH lt 11) because iodine interacts with hydroxide ions toform nonactive iodate ion IO
3
minus in higher alkaline solution[34]
3I2
+ 6OHminus 997888rarr IO3
minus
+ 5Iminus + 3H2
O (19)
However borohydride ions are insufficiently stable atroom temperature when pH lt 11 Table 1 comprises approx-imate rates of BH
4
minus decomposition due to hydrolysis Onecan see that the fuel with alkalinity above 2molsdotLminus1 is almostnot subjected to hydrolysis at 25∘C The same applies to theiodometric redox titrationmethod used by us which requiresa 1molsdotLminus1 NaOH solution In a 1molsdotLminus1 alkaline solutionthe addition of iodine to borohydride is also accompanied byextremely slight hydrogen release as a result of borohydridedecomposition Under these conditions about 05ndash1 ofBH4
minus ions is decomposed while a negligible amount ofiodate is formed by reaction (18) with iodine consumptionof sim05ndash1 Thus any mistakes are compensated and directiodometric titration allows one to obtain the result closest tothe true value of borohydride concentration (the error not toexceed 005)
33 Processing Titration Curves and Estimation of AccuracyThe titration curves pH versus119881
119905
and the appropriate depen-dences 119889pH119889119881
119905
versus 119881119905
obtained by acid-base titration ofaqueous solutions of various anion mixtures are shown inFigure 1 and the analogous curves obtained by iodometrictitration are shown in Figure 2 The first distinct step pre-sented (not always) on the iodometric titration curve reflectsa complex mechanism of the chemical reaction (18) and isneglected The determination of the amount of the titrantis carried out by the second sharp leap within the potentialrange 0 to 600mV (Figure 2)
The titration curves were processed by two ways namelya simple method of differentiation and a more complexmethod of computer simulations For the iodometric deter-mination of borohydride it is enough to use the method ofdifferentiation only while for acid-base titration the bestresults are obtained when both methods (differentiation andsimulation) are used
Themethod of differentiation is based on the equivalencepoints coinciding with the inflections on the pH versus119881119905
curve and with appropriate maxima on the differential119889pH119889119881
119905
versus 119881119905
curve (Figure 1) The positions of themaximum points 119881lowast
119905
are fixed the titrant volume consumedfor titration of the 119894th component Δ119881lowast
119905
= 119881lowast
119905119894
minus 119881lowast
119905119894minus1
ismeasured and the amount of each component is calculatedHowever in few complex cases it is possible to state thatan extreme point on the differential 1198892pH119889(119881
119905
)2 = 0 curve
is close to an equivalence point at sharp changes of pH Ifsmoothed inflections with a small pH difference are observedor two points of inflection are near each other a significantsystematic error arises
The method of simulation is based on the theoryexplained aboveThe program for calculating titration curvesuses the appropriate theoretical equations (10)ndash(17) and com-bines the experimental pH versus119881
119905
curvewith the calculated
Journal of Fuels 5
0
2
4
6
8
10
12
14
0 4 8 12
pH
ExperimentCalculationDifferentiation
Vt (mL)
minus100
900
1900
2900
3900
4900
dpH
dVt
OH minus
(a)
0
20
40
60
80
100
120
0
2
4
6
8
10
12
14
0 2 4 6 8 10 12 14
pH
ExperimentCalculationDifferentiation
Vt (mL)
dpH
dVt
OHminus+ CO3
2minus
(b)
0
20
40
60
80
100
120
0
4
8
12
16
0 1 2 3 4 5 6
pH
ExperimentCalculationDifferentiation
Vt (mL)
dpH
dVt
OHminus+ BH4
minus+ BO2
minus
(c)
20
0
40
60
80
100
120
0
2
4
6
8
10
12
14
0 2 4 6 8
pH
ExperimentCalculationDifferentiation
Vt (mL)
dpH
dVt
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
(d)
Figure 1 Calculated titration curves experimental titration curves and the corresponding 119889pH119889119881119905
versus 119881119905
curves for aqueous solutionsof several mixtures of anions (a) OHminus (b) OHminus + CO
3
2minus (c) OHminus + BH4
minus or OHminus + BO2
minus or OHminus + BH4
minus
+ BO2
minus (d) OHminus + BH4
minus
+
BO2
minus
+ CO3
minus
pH versus 119881calc one The variable parameters are the soughtquantities of components in the aliquot 119899OHminus 119899BH
4
minus+BO2
minus and119899CO3
2minus The criterion of optimum is the minimum dispersion
1198782
=sum119870
119896=1
(pH119896
minus pHcalc119896)2
119870 minus 1
=sum119870
119896=1
((119889pH119889119881119905119896
) (119881119905119896
minus 119881calc119896))2
119870 minus 1
(20)
Here119870 is the number of points on the titration curve Figure 1shows the experimental and calculated titration curves forfew solutions of various multicomponent mixtures It is
visible that the applied computational methods allow exactsimulating experimental curves
Error Analysis and Estimation of AccuracyAnumber of refer-ence solutions of a desired composition were prepared usingKBO2
NaBH4
KBH4
NaOHKOHNa2
CO3
andK2
CO3
forvalidation of our analytical methodology (the concentrationranges of each analyzed ion in the considered samples arepresented in Table 2) In order to detect systematic errorsthe dependences of the ldquomeasuredweightedrdquo ratios on theanionic fraction 120596
119894
were plotted (120596119894
is the mole fraction ofthe 119894th anion in the total amount of the analyzed anions 120596varies from 0 up to 1) The results are given in Figure 3 Theaverage value of the ldquomeasuredweightedrdquo ratio for each ionis presented in Table 3
6 Journal of Fuels
Table 2 Considered concentration ranges of analyzed ions in thesample
Ion Concentration range in the analyzed sample molsdotLminus1
OHminus 002ndash12BH4
minus 002ndash02BO2
minus 005ndash02CO3
2minus 0008ndash01
It is apparent from Table 3 that the simulation methodalso gives a systematic error The causes can be simplificationof the theory the impossibility to consider all side processesthe inability to exactly calculate activity coefficients and soforth so the shape of the calculated curve may not com-pletely coincide with the experimental curve In particularin the titration process of borate solutions the formationof poliborates and their hydrated forms is possible In thecase of simulation the lower branch of the titration curveshould be limitedwhen all equivalence points are passed overAccelerated titration or cold solutionmay cause an additionalerror due to the inhibition of reaction (6) and the failure ofchemical equilibrium
The concentration of OHminus ions is estimated with an accu-racy of 0959 and 0956 for the differentiation and simulationmethods respectivelyThe total of (BH
4
minus
+BO2
minus) is estimatedwith an accuracy of 1023 and 1012 for the differentiationand simulation methods respectively (Table 3) Thus for theOHminus+BH
4
minus
+BO2
minus system the differentiation and simulationmethods give similar results and have no advantages overeach other and the systematic error is small but naturallyincreases with decreasing share of the analyzed ionThe trendof the systematic error is shown in Figure 3(a) by means ofsolid lines Both methods overestimate the content of boronin the sample and underestimate the content of alkali Forcompensation of the systematic error the following equationshave been obtained for the method of differentiation
120573OHminus = [138 minus 04120596minus005
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [120596minus005
BH4
minus+BO2
minus minus 0025]minus1
(21)
and for the method of simulation
120573OHminus = [139 minus 04120596minus008
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [07120596minus005
BH4
minus+BO2
minus + 028]minus1
(22)
After analysis and the determination of the components119899OHminus and 119899BH
4
minus+BO2
minus a correction procedure was carried outby multiplying the values 119899
119894
found by the correspondingcorrection coefficients 120573
119894
calculated from formulae (21) or(22) Finally the corrected amounts of the 119894th component inthe sample 119899
119894cor are
119899119894cor = 120573119894119899119894 (23)
Figure 3(b) shows the result of correction of the data given inFigure 3(a)The systematic error was totally compensated forall the variants of analysis (Table 3)
0 2 4 6 8 10Vt (mL)
minus600
minus200
200
600
1000
E(m
V)
Vlowastt
minus27000
minus18000
minus9000
0
9000
dEdVt
Figure 2 Curve of direct iodometric titration of borohydride ionsin an aqueous solution with the mixture of anions OHminus + BH
4
minus
+
BO2
minus
+ CO3
2minus (119881lowast119905
is equivalence point)
When the value of the anionic fraction 04 lt 120596119894
lt 1 allpoints lie within the ldquomeasuredweightedrdquo range 095ndash105that is the random error does not exceed 5 all points liewithin the range 088ndash112 when 005 lt 120596
119894
lt 04 that isthe random error does not exceed 12 It is only possibleto perform semiquantitative analysis of any component at itsvery small content in the mixture (120596
119894
lt 002) On correctionthe average accuracy parameter of the OHminus concentrationis 1000 for differentiation and 1001 for simulation and theaverage accuracy parameter for the (BH
4
minus
+ BO2
minus
) total is1008 for differentiation and 1004 for simulation (Table 3)
The feature of titration of alkaline-carbonate solutionsis the existence of three leaps on the titration curve(Figure 1(b))The first leap belongs to alkali while the secondand third ones are due to carbonates Correspondingly whenthe quantities of components are determined by the locationof peaks on the differential curve the quantity of CO
3
2minus isincluded twiceThe analysis of carbonate bymeans of the sec-ond peak gives a worse result than by the third one At a verysmall content of carbonate the second peak is not detectedThe average ldquomeasuredweightedrdquo value is 1215 for CO
3
2minus
ions by the second peak on the differential curve and 1115in the case of the third peak and the ldquomeasuredweightedrdquovalue is 1089 for the method of simulation The results ofcontrol determination of the alkali and carbonate contents inthe reference solutions OHminus + CO
3
2minus are shown in Figures3(c) and 3(d) for the two methods as the dependence ofthe accuracy parameter on the anionic fractions 120596
119894
In allcases the points of differentiation are more distant fromthe ldquocorrectrdquo level than those of simulation Consequentlythe method of simulation gives more correct results for theOHminus + CO
3
2minus system while the method of determinationcannot be recommended because of its high systematic errorsin carbonate analysis
The systematic error naturally increases with decreasingfractions of the analyzed ions In Figure 3(c) the trend ofsystematic errors is shown by means of solid lines for the
Journal of Fuels 7
Table 3 Average values of the ldquomeasuredweightedrdquo ratios for each ion in the mixture before and after correction of systematic errors
System Ions Method ldquoMeasuredweightedrdquo ratioBefore correction After correction
OHminus + BH4
minus + BO2
minus
OHminus Differentiation 0959 1000Simulation 0956 1001
BH4
minus + BO2
minus
Differentiation 1023 1008Simulation 1012 1004
OHminus + CO3
2minus
OHminus Simulation 0985 1003CO3
2minus Simulation 1089 0996
OHminus + BH4
minus + BO2
minus + CO3
2minus
OHminus Simulation 0874 0958BH4
minus + BO2
minus Simulation 1040 0992CO3
2minus Simulation 0934 1008
08
09
1
11
12
13
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ BH4
minus+ BO2
minus
OHminus simulationBH4
minus+ BO2
minus simulationNormOHminus differentiationBH4
minus+ BO2
minus differentiation
(a)
08
09
1
11
12
13
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ BH4
minus+ BO2
minus
OHminus simulationBH4
minus+ BO2
minus simulation + correctionNormOHminus differentiation + correctionBH4
minus+ BO2
minus differentiation + correction
(b)
05060708091
1112131415
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ CO3
2minus
OHminus simulation
NormCO3
2minus simulation
(c)
07
08
09
1
11
12
13
14
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ CO3
2minus
simulation + correctionOHminus
Normsimulation + correctionCO3
2minus
(d)
0
02
04
06
08
1
12
14
0 02 04 06 08 1
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
OHminus simulationBH4
minus+ BO2
minus simulationNormOHminus differentiation
CO32minus simulation
CO32minus differentiation
120596i
Measuredweighted
BH4minus+ BO2
minus+ CO3
2minus differentiation
(e)
Measuredweighted
02
04
06
08
1
12
14
0 02 04 06 08 1120596i
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
BH4minus+ BO2
minus simulation + correctionOHminus simulation + correction
Normsimulation + correctionCO3
2minus
(f)
Figure 3 Dependence of the ldquomeasuredweightedrdquo ratios for anions on their mole fraction 120596119894
in the mixture (a) for the OHminus + BH4
minus
+
BO2
minus system before correction of systematic errors (b) for the OHminus + BH4
minus
+ BO2
minus system after correction of systematic errors (c) for theOHminus +CO
3
2minus system before correction of systematic errors (d) for the OHminus +CO3
2minus system after correction of systematic errors (e) for theOHminus + BH
4
minus
+ BO2
minus
+CO3
2minus system before correction of systematic errors (f) for the OHminus + BH4
minus
+ BO2
minus
+CO3
2minus system after correctionof systematic errors The solid lines show the average trend of errors The dotted lines show the error interval for the method of simulation
8 Journal of Fuels
method of simulation The following equations have beensuggested for compensation of this trend
120573OHminus = [29 minus 19120596minus0055
OHminus ]minus1
120573CO3
2minus = [75120596minus001
CO3
2minus minus 65]minus1
(24)
After analysis and the determination of the 119899OHminus and 119899CO3
2minus
values a correction procedure is carried out by formula(24) Figure 3(d) shows the result of such correction Thesystematic error is completely compensated (Table 3) Allpoints lie within the ldquomeasuredweightedrdquo range 095ndash105for the anionic fractions within 04 lt 120596
119894
lt 1 that is therandom error does not exceed 5 and the random scatteringdoes not exceed 12 when 015 lt 120596
119894
lt 04 If the fractionof carbonate is less than 015 the reliability of its analysisdecreases because of the high random dispersion thereforeit is required to increase the number of replicate samplesThedirect titrimetric analysis of carbonate becomes impossiblewhen 120596CO
3
2minus lt 0015A feature of titration of alkaline-borohydride-borate-
carbonate solutions is the existence of three weak leaps onthe titration curve (Figure 1(d)) The first leap belongs toalkali while the second belongs to the ldquoBH
4
minus
+ BO2
minus
+
CO3
2minusrdquo total and the third one belongs to carbonate ionsRespectively at the quantification of components by meansof the position of peaks on the differential curve the totalcontent of boron 119899BH
4
minus+BO2
minus can be only calculated after thedetermination and extraction of the carbonate quantity
The results of our control determination of the anioncontents in the OHminus + BH
4
minus
+ BO2
minus
+ CO3
2minus mixturesby both methods are shown in Figure 3(e) The methodof differentiation gives an unsatisfactory result for car-bonate underestimating its content significantly the meanldquomeasuredweightedrdquo value being 0615 The carbonate peakdisappears when 120596CO
3
2minus lt 015 which leads to incorrectdetermination of the BH
4
minus
+ BO2
minus total Therefore for theOHminus+ BH
4
minus
+ BO2
minus
+ CO3
2minus system (the highly carbonatedand discharged fuel) the method of differentiation cannotbe recommended because of its large systematic errors incarbonate analysis and the method of simulation is onlysuggested for use The mean ldquomeasuredweightedrdquo values areshown in Table 3 The determination accuracy is 0874 forOHminus ions 1040 for the BH
4
minus
+ BO2
minus total and 0934 forCO3
2minus ions After correction these parameters become 09580992 and 1008 respectively The correcting coefficients are
120573OHminus = [198 minus 120596minus005
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [120596minus0085
BH4
minus+BO2
minus minus 003]minus1
120573CO3
2minus = [195 minus 120596minus001
CO3
2minus]minus1
(25)
The systematic error is thus compensated however therandom scattering of the points is higher than with moresimple options The random dispersion for alkali and borondoes not exceed 15 (all points arewithin 085ndash115) howeverit is only fair for carbonatewhen120596CO
3
2minus gt 01 If the carbonate
content is less than 01 its semiquantitative analysis is onlypossible But very small amounts of carbonate will not affectthe functioning of DBFC and only higher concentrations ofcarbonate exceeding the solubility limit can be deposited inthe electrode to hinder the functioning of DBFC
4 Conclusions
Theanalytic technique presented in our paper includes takinga small fuel sample from DBFC and performing two types oftitrations (acid-base and iodometric ones) which supplementeach otherThenecessity of exactly two techniques of titrationis due to the fact that iodometric titration determines theBH4
minus quantity in the sample only while the quantities ofother fuel components are provided by acid-base titration(OHminus BO
2
minus CO3
2minus)Therefore the joint application of thesetitration techniques allows one to most fully quantify thecurrent state of fuel in the process of DBFC functioningThe determination correctness of the technique has beenshown on artificial mixtures with a wide variation of theircomposition The average error depends on the number ofcomponents and their ratio in the mixture The investigationresults show that in the most complex case of highly carbon-ated and discharged fuel the maximal error of determinationdoes not exceed 15
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgment
The authors would like to gratefully acknowledge the RussianFoundation for Basic Research for financial support (Projectno 12-03-31802)
References
[1] J B Lakeman A Rose K D Pointon et al ldquoThe directborohydride fuel cell for UUV propulsion powerrdquo Journal ofPower Sources vol 162 no 2 pp 765ndash772 2006
[2] C P de Leon F C Walsh D Pletcher D J Browning and JB Lakeman ldquoDirect borohydride fuel cellsrdquo Journal of PowerSources vol 155 no 2 pp 172ndash181 2006
[3] R Aiello J H Sharp and M A Matthews ldquoProduction ofhydrogen from chemical hydrides via hydrolysis with steamrdquoInternational Journal of Hydrogen Energy vol 24 no 12 pp1123ndash1130 1999
[4] S C Amendola S L Sharp-Goldman M S Janjua et al ldquoSafeportable hydrogen gas generator using aqueous borohydridesolution and Ru catalystrdquo International Journal of HydrogenEnergy vol 25 no 10 pp 969ndash975 2000
[5] H I Schlesinger H C Brown A E Finholt J R GilbreathH R Hoekstra and E K Hyde ldquoSodium borohydride itshydrolysis and its use as a reducing agent and in the generationof hydrogenrdquo Journal of the American Chemical Society vol 75no 1 pp 215ndash219 1953
Journal of Fuels 9
[6] S C Amendola P Onnerud M T Kelly P J Petillo S LSharp-Goldman and M Binder ldquoNovel high power densityborohydride-air cellrdquo Journal of Power Sources vol 84 no 1 pp130ndash133 1999
[7] B H Liu and Z P Li ldquoCurrent status and progress of directborohydride fuel cell technology developmentrdquo Journal ofPower Sources vol 187 no 2 pp 291ndash297 2009
[8] B H Liu and Z P Li ldquoA review hydrogen generation fromborohydride hydrolysis reactionrdquo Journal of Power Sources vol187 no 2 pp 527ndash534 2009
[9] B Weng Z Wu Z Li H Yang and H Leng ldquoHydrogengeneration from noncatalytic hydrolysis of LiBH4NH3BH3mixture for fuel cell applicationsrdquo International Journal ofHydrogen Energy vol 36 no 17 pp 10870ndash10876 2011
[10] A E Sanli I Kayacan B Z Uysal and M L Aksu ldquoRecoveryof borohydride from metaborate solution using a silver catalystfor application of direct rechargable borohydrideperoxide fuelcellsrdquo Journal of Power Sources vol 195 no 9 pp 2604ndash26072010
[11] R Jamard J Salomon A Martinent-Beaumont and CCoutanceau ldquoLife time test in direct borohydride fuel cellsystemrdquo Journal of Power Sources vol 193 no 2 pp 779ndash7872009
[12] J-H Wee ldquoA comparison of sodium borohydride as a fuel forproton exchange membrane fuel cells and for direct borohy-dride fuel cellsrdquo Journal of Power Sources vol 155 no 2 pp329ndash339 2006
[13] A V Churikov K V Zapsis V V Khramkov M A ChurikovM P Smotrov and I A Kazarinov ldquoPhase diagrams of theternary systems NaBH
4
+ NaOH + H2
O KBH4
+ KOH + H2
ONaBO
2
+ NaOH + H2
O and KBO2
+ KOH + H2
O at minus10∘CrdquoJournal of Chemical and Engineering Data vol 56 no 1 pp 9ndash13 2011
[14] A V Churikov K V Zapsis V V Khramkov M A Churikovand I M Gamayunova ldquoTemperature-induced transformationof the phase diagrams of ternary systems NaBO
2
+ NaOH+ H2
O and KBO2
+ KOH + H2
Ordquo Journal of Chemical andEngineering Data vol 56 no 3 pp 383ndash389 2011
[15] A V Churikov K V Zapsis A V Ivanishchev and V OSychova ldquoTemperature-induced transformation of the phasediagrams of ternary systems NaBH
4
+ NaOH +H2
O and KBH4
+ KOH + H2
Ordquo Journal of Chemical and Engineering Data vol56 no 5 pp 2543ndash2552 2011
[16] G Rostamikiaa and M J Janik ldquoDirect borohydride oxidationmechanism determination and design of alloy catalysts guidedby density functional theoryrdquo Energy amp Environmental Sciencevol 3 pp 1262ndash1274 2010
[17] B Sljuki J Miliki D M F Santosa and C A C SequeiraldquoCarbon-supported Pt
075
M025
(M = Ni or Co) electrocatalystsfor borohydride oxidationrdquo Electrochim Acta vol 107 pp 577ndash583 2013
[18] B H Liu J Q Yang and Z P Li ldquoConcentration ratio of[OHminus][BH
4
minus] a controlling factor for the fuel efficiency ofborohydride electro-oxidationrdquo International Journal of Hydro-gen Energy vol 34 no 23 pp 9436ndash9443 2009
[19] A V Churikov A V Ivanishchev I M Gamayunova andA V Ushakov ldquoDensity calculations for (Na K)BH
4
+ (NaK)BO
2
+ (Na K)OH + H2
O solutions used in hydrogen powerengineeringrdquo Journal of Chemical and Engineering Data vol 56no 11 pp 3984ndash3993 2011
[20] A V Churikov V O Romanova M A Churikov and I MGamayunova ldquoThemodel of fuel transformation at discharge of
direct borohydride fuel cellrdquo International Review of ChemicalEngineering vol 4 pp 263ndash268 2012
[21] A V Churikov I M Gamayunova K V Zapsis M AChurikov and A V Ivanishchev ldquoInfluence of temperature andalkalinity on the hydrolysis rate of borohydride ions in aqueoussolutionrdquo International Journal of Hydrogen Energy vol 37 no1 pp 335ndash344 2012
[22] Z P Li B H Liu K Arai and S Suda ldquoA fuel cell developmentfor using borohydrides as the fuelrdquo Journal of the Electrochemi-cal Society vol 150 no 7 pp A868ndashA872 2003
[23] Y Wang P Hea and H Zhou ldquoA novel direct borohydridefuel cell using an acid-alkaline hybrid electrolyterdquo Energy ampEnvironmental Science vol 3 no 10 pp 1515ndash1518 2010
[24] J Ma N A Choudhury and Y Sahai ldquoA comprehensive reviewof direct borohydride fuel cellsrdquo Renewable and SustainableEnergy Reviews vol 14 no 1 pp 183ndash199 2010
[25] R Bruhlmann and L Piatti ldquoAn improved method for thetitrimetric determination of boron in ironrdquo Chimia vol 11 p203 1957
[26] A Keshan and C Bimba ldquoCobalt-potassium and ammonium-cobalt dodecaboraterdquo Izvestiya Akademii Nauk Latvijskoj SSRp 115 1954
[27] J Czakow T Steciak and O Szczebinska ldquoThe spectral deter-mination of trace amounts of impurities in the solutions withthe metal electrodes in the spark moderdquo Analytical Chemistryvol 3 p 745 1958
[28] R Rosotti ldquoA fast method for the determination of traceamounts of boron in the steelrdquo Analytical Chemistry vol 44 p208 1962
[29] J Varka and A Sklaf ldquoApplication of potentiometric titrationIV Determination of B
2
O3
in glass enamels and boron-containing raw materialsrdquo Keramik vol 7 p 12 1957
[30] D E Williams and J Vilamis ldquoStability of the curcumincomplex in boron determinationrdquoAnalytical Chemistry vol 33pp 1098ndash1100 1961
[31] S Kertes and M Lederer ldquoPaper chromatography of inorganicions Rf values in mixtures of butanol and Hbrrdquo AnalyticaChimica Acta vol 15 no C pp 543ndash547 1956
[32] A A Nemodruk and Z K Karalova The Analytical Chemistryof Boron Nauka 1964
[33] C A Parker ldquoRaman spectra in spectrofluorimetryrdquo The Ana-lyst vol 84 no 1000 pp 446ndash453 1959
[34] C A Parker and W J Barnes ldquoFluorimetric determination ofboron application to silicon sea water and steelrdquo The Analystvol 85 no 1016 pp 828ndash838 1960
[35] M V Akhmanova Methods of Determination and Analysis ofRear Elements Izdat Akademija Nauk SSSR 1961
[36] E H Jensen A Study on Sodium Borohydride Nyt NordiskForlag Amold Busck Copenhagen Denmark 1954
[37] I Fatt and M Tashima Alkali Metal Dispersions D VanNostrand Co Inc Princeton NJ USA 1961
[38] DA Lyttle EH Jensen andWA Struck ldquoA simple volumetricassay for sodium borohydriderdquo Analytical Chemistry vol 24no 11 pp 1843ndash1844 1952
[39] P K Norkus ldquoIodometric determination of borohydriderdquoRussian Journal of Analytical Chemistry vol 23 pp 908ndash9111968
[40] N N Malrsquoceva and V S Khain Sodium Borohydride Propertiesand Application Nauka 1985
10 Journal of Fuels
[41] C Harzdorf and O Steinhauser ldquoZur photometrisehen Titra-tion von Fluorid mit Thoriumnitratrdquo Freseniusrsquo Zeitschrift furAnalytische Chemie vol 210 no 2 pp 106ndash112 1965
[42] W D Davis L S Mason and G Stegeman ldquoThe heats offormation of sodium borohydride lithium borohydride andlithium aluminum hydriderdquo Journal of the American ChemicalSociety vol 71 no 8 pp 2775ndash2781 1949
[43] S W Chaikin ldquoDirect volumetric assay of sodium borohydrideand potassium borohydriderdquo Analytical Chemistry vol 25 no5 pp 831ndash832 1953
[44] U Ulku and G Somer ldquoDetermination of trace borohydride inbasic solutions using differential pulse polarographyrdquo TurkishJournal of Chemistry vol 33 pp 657ndash665 2009
[45] H Celikkan H Aydin and M L Aksu ldquoThe electroanalyticaldetermination of sodium borohydride using a gold electroderdquoTurkish Journal of Chemistry vol 29 pp 519ndash524 2005
[46] M V Mirkin and A J Bard ldquoVoltammetric method forthe determination of borohydride concentration in alkalineaqueous solutionsrdquoAnalytical Chemistry vol 63 no 5 pp 532ndash533 1991
[47] D M F Santos and C A C Sequeira ldquoPotentiometric moni-toring of sodium borohydride in aqueous solutionsrdquo Ciencia sTecnologia dos Materials vol 20 no 3-4 pp 31ndash34 2008
[48] D M F Santos and C A C Sequeira ldquoSodium borohydridedetermination by measurement of open circuit potentialsrdquoJournal of Electroanalytical Chemistry vol 627 pp 1ndash8 2009
[49] H C Brown and A C Boyd Jr ldquoArgentimetric procedure forborohydride determinationrdquo Analytical Chemistry vol 27 no1 pp 156ndash158 1955
[50] V B Breicis A O Berzina and L K Lepin ldquoPotentiomet-ric titration of water solutions of sodium borohydride byhydrochloric acidrdquo Scientific Short Letter of Riga PolytechnicInstitute vol 15 pp 179ndash188 19651966
[51] U U Lurie Handbook on Analytical Chemistry Khimiya 1979[52] R A Lidin L L Andreeva and V A Molochko Hand-
book of Inorganic Chemistry Constants of Inorganic SubstancesKhimiya 1987
[53] R A Robinson and R H Stokes Electrolyte Solutions the Mea-surement and Interpretation of Conductance Chemical Potentialand Diffusion in Solutions of Simple Electrolytes ButterworthsLondon UK 1959
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
StructuresJournal of
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear InstallationsScience and Technology of
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Wind EnergyJournal of
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Nuclear EnergyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
4 Journal of Fuels
[HCO3
minus
] =119862carb
1 + 1198912 [H+] 1198701
+ 1198702
1198914 [H+]
[H2
CO3
] =119862carb
1 + (1198701
1198912 [H+]) (1 + 1198702
1198914 [H+])
(14)
where
[H+] = 119891minus110minuspH (15)
Here the ionic product of water (autoprotolysis constant)is 119870119882
= 1198912 [OH]sdot[H] = 1 times 10
minus14 at 25∘C [52] thedissociation constant of metaboric acid HBO
2
is 119870B =
1198912
(([BO2
] sdot [H])[HBO2
]) the dissociation constant ofcarbonic acid H
2
CO3
at the first stage is 1198701
= 1198912
(([HCO3
] sdot
[H])[H2
CO3
]) = 445 times 10minus7 at 25∘C [52] the dissociation
constant of carbonic acid H2
CO3
at the second stage is 1198702
=
1198914
(([CO3
] sdot [H])[HCO3
]) = 469 times 10minus11 at 25∘C [52]
Moreover processing the titration curves of simple solutionsof a fixed composition (eg 001molsdotLminus1 NaBO
2
) can be usedfor refinement of these dissociation constants
Let us determine the calculated volume 119881calc of thetitrant from the material balance by acid by boron andby carbon only considering the acid consumption by thetitration reactions (5) (7)ndash(9)Thematerial balance equationis thus written as
119862119905
= [H+] + (119862alc minus [OHminus
])
+ [HBO2
] + [HCO3
minus
] + 2 times [H2
CO3
] (16)
(the initial content of acid in an alkaline solution [H+]0 lt10minus11molsdotLminus1 is ignored)The calculated value of119881calc is estimated from the current
pH value and (10) and (15) As a result the calculated pointsof the titration curve of solutions containing a mixture ofanions OHminus BH
4
minus BO2
minus and CO3
2minus are determined by theequation
119881calc =119881
119873HCl([H+] + Calc minus [OH
minus
] + 119862119861
minus [BH4
minus
]
minus [BO2
minus
] + [HCO3
minus
] + 2 times [H2
CO3
])
(17)
where the current equilibrium values ofmolar concentrationsare determined by (14) and (15) Equation (17) is veryconvenient for computer simulations It allows calculatingthe pH minus 119881calc dependence and plotting the whole calculatedtitration curve By means of fitting the calculated curve to theexperimental curve we find the amounts of components inthe sample 119899OHminus 119899BH
4
minus+BO2
minus and 119899CO3
2minus The concentrationof borate is calculated by the difference of total boron minusborohydride that is 119899BO
2
minus = 119899BH4
minus+BO2
minus minus 119899BH4
minus The amountof borohydride in the mixture is selectively determined byiodometric titration
32 Determination of Borohydride in Solution by IodometricTitration As shown in [39] the quantification of BH
4
minus
in solution by direct iodometric titration is based on thereaction proceeding quantitatively in an alkaline medium
4I2
+ BH4
minus
+ 8OHminus = BO2
minus
+ 8Iminus + 6H2
O (18)
Usually the direct titration is made in a low alkaline medium(pH lt 11) because iodine interacts with hydroxide ions toform nonactive iodate ion IO
3
minus in higher alkaline solution[34]
3I2
+ 6OHminus 997888rarr IO3
minus
+ 5Iminus + 3H2
O (19)
However borohydride ions are insufficiently stable atroom temperature when pH lt 11 Table 1 comprises approx-imate rates of BH
4
minus decomposition due to hydrolysis Onecan see that the fuel with alkalinity above 2molsdotLminus1 is almostnot subjected to hydrolysis at 25∘C The same applies to theiodometric redox titrationmethod used by us which requiresa 1molsdotLminus1 NaOH solution In a 1molsdotLminus1 alkaline solutionthe addition of iodine to borohydride is also accompanied byextremely slight hydrogen release as a result of borohydridedecomposition Under these conditions about 05ndash1 ofBH4
minus ions is decomposed while a negligible amount ofiodate is formed by reaction (18) with iodine consumptionof sim05ndash1 Thus any mistakes are compensated and directiodometric titration allows one to obtain the result closest tothe true value of borohydride concentration (the error not toexceed 005)
33 Processing Titration Curves and Estimation of AccuracyThe titration curves pH versus119881
119905
and the appropriate depen-dences 119889pH119889119881
119905
versus 119881119905
obtained by acid-base titration ofaqueous solutions of various anion mixtures are shown inFigure 1 and the analogous curves obtained by iodometrictitration are shown in Figure 2 The first distinct step pre-sented (not always) on the iodometric titration curve reflectsa complex mechanism of the chemical reaction (18) and isneglected The determination of the amount of the titrantis carried out by the second sharp leap within the potentialrange 0 to 600mV (Figure 2)
The titration curves were processed by two ways namelya simple method of differentiation and a more complexmethod of computer simulations For the iodometric deter-mination of borohydride it is enough to use the method ofdifferentiation only while for acid-base titration the bestresults are obtained when both methods (differentiation andsimulation) are used
Themethod of differentiation is based on the equivalencepoints coinciding with the inflections on the pH versus119881119905
curve and with appropriate maxima on the differential119889pH119889119881
119905
versus 119881119905
curve (Figure 1) The positions of themaximum points 119881lowast
119905
are fixed the titrant volume consumedfor titration of the 119894th component Δ119881lowast
119905
= 119881lowast
119905119894
minus 119881lowast
119905119894minus1
ismeasured and the amount of each component is calculatedHowever in few complex cases it is possible to state thatan extreme point on the differential 1198892pH119889(119881
119905
)2 = 0 curve
is close to an equivalence point at sharp changes of pH Ifsmoothed inflections with a small pH difference are observedor two points of inflection are near each other a significantsystematic error arises
The method of simulation is based on the theoryexplained aboveThe program for calculating titration curvesuses the appropriate theoretical equations (10)ndash(17) and com-bines the experimental pH versus119881
119905
curvewith the calculated
Journal of Fuels 5
0
2
4
6
8
10
12
14
0 4 8 12
pH
ExperimentCalculationDifferentiation
Vt (mL)
minus100
900
1900
2900
3900
4900
dpH
dVt
OH minus
(a)
0
20
40
60
80
100
120
0
2
4
6
8
10
12
14
0 2 4 6 8 10 12 14
pH
ExperimentCalculationDifferentiation
Vt (mL)
dpH
dVt
OHminus+ CO3
2minus
(b)
0
20
40
60
80
100
120
0
4
8
12
16
0 1 2 3 4 5 6
pH
ExperimentCalculationDifferentiation
Vt (mL)
dpH
dVt
OHminus+ BH4
minus+ BO2
minus
(c)
20
0
40
60
80
100
120
0
2
4
6
8
10
12
14
0 2 4 6 8
pH
ExperimentCalculationDifferentiation
Vt (mL)
dpH
dVt
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
(d)
Figure 1 Calculated titration curves experimental titration curves and the corresponding 119889pH119889119881119905
versus 119881119905
curves for aqueous solutionsof several mixtures of anions (a) OHminus (b) OHminus + CO
3
2minus (c) OHminus + BH4
minus or OHminus + BO2
minus or OHminus + BH4
minus
+ BO2
minus (d) OHminus + BH4
minus
+
BO2
minus
+ CO3
minus
pH versus 119881calc one The variable parameters are the soughtquantities of components in the aliquot 119899OHminus 119899BH
4
minus+BO2
minus and119899CO3
2minus The criterion of optimum is the minimum dispersion
1198782
=sum119870
119896=1
(pH119896
minus pHcalc119896)2
119870 minus 1
=sum119870
119896=1
((119889pH119889119881119905119896
) (119881119905119896
minus 119881calc119896))2
119870 minus 1
(20)
Here119870 is the number of points on the titration curve Figure 1shows the experimental and calculated titration curves forfew solutions of various multicomponent mixtures It is
visible that the applied computational methods allow exactsimulating experimental curves
Error Analysis and Estimation of AccuracyAnumber of refer-ence solutions of a desired composition were prepared usingKBO2
NaBH4
KBH4
NaOHKOHNa2
CO3
andK2
CO3
forvalidation of our analytical methodology (the concentrationranges of each analyzed ion in the considered samples arepresented in Table 2) In order to detect systematic errorsthe dependences of the ldquomeasuredweightedrdquo ratios on theanionic fraction 120596
119894
were plotted (120596119894
is the mole fraction ofthe 119894th anion in the total amount of the analyzed anions 120596varies from 0 up to 1) The results are given in Figure 3 Theaverage value of the ldquomeasuredweightedrdquo ratio for each ionis presented in Table 3
6 Journal of Fuels
Table 2 Considered concentration ranges of analyzed ions in thesample
Ion Concentration range in the analyzed sample molsdotLminus1
OHminus 002ndash12BH4
minus 002ndash02BO2
minus 005ndash02CO3
2minus 0008ndash01
It is apparent from Table 3 that the simulation methodalso gives a systematic error The causes can be simplificationof the theory the impossibility to consider all side processesthe inability to exactly calculate activity coefficients and soforth so the shape of the calculated curve may not com-pletely coincide with the experimental curve In particularin the titration process of borate solutions the formationof poliborates and their hydrated forms is possible In thecase of simulation the lower branch of the titration curveshould be limitedwhen all equivalence points are passed overAccelerated titration or cold solutionmay cause an additionalerror due to the inhibition of reaction (6) and the failure ofchemical equilibrium
The concentration of OHminus ions is estimated with an accu-racy of 0959 and 0956 for the differentiation and simulationmethods respectivelyThe total of (BH
4
minus
+BO2
minus) is estimatedwith an accuracy of 1023 and 1012 for the differentiationand simulation methods respectively (Table 3) Thus for theOHminus+BH
4
minus
+BO2
minus system the differentiation and simulationmethods give similar results and have no advantages overeach other and the systematic error is small but naturallyincreases with decreasing share of the analyzed ionThe trendof the systematic error is shown in Figure 3(a) by means ofsolid lines Both methods overestimate the content of boronin the sample and underestimate the content of alkali Forcompensation of the systematic error the following equationshave been obtained for the method of differentiation
120573OHminus = [138 minus 04120596minus005
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [120596minus005
BH4
minus+BO2
minus minus 0025]minus1
(21)
and for the method of simulation
120573OHminus = [139 minus 04120596minus008
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [07120596minus005
BH4
minus+BO2
minus + 028]minus1
(22)
After analysis and the determination of the components119899OHminus and 119899BH
4
minus+BO2
minus a correction procedure was carried outby multiplying the values 119899
119894
found by the correspondingcorrection coefficients 120573
119894
calculated from formulae (21) or(22) Finally the corrected amounts of the 119894th component inthe sample 119899
119894cor are
119899119894cor = 120573119894119899119894 (23)
Figure 3(b) shows the result of correction of the data given inFigure 3(a)The systematic error was totally compensated forall the variants of analysis (Table 3)
0 2 4 6 8 10Vt (mL)
minus600
minus200
200
600
1000
E(m
V)
Vlowastt
minus27000
minus18000
minus9000
0
9000
dEdVt
Figure 2 Curve of direct iodometric titration of borohydride ionsin an aqueous solution with the mixture of anions OHminus + BH
4
minus
+
BO2
minus
+ CO3
2minus (119881lowast119905
is equivalence point)
When the value of the anionic fraction 04 lt 120596119894
lt 1 allpoints lie within the ldquomeasuredweightedrdquo range 095ndash105that is the random error does not exceed 5 all points liewithin the range 088ndash112 when 005 lt 120596
119894
lt 04 that isthe random error does not exceed 12 It is only possibleto perform semiquantitative analysis of any component at itsvery small content in the mixture (120596
119894
lt 002) On correctionthe average accuracy parameter of the OHminus concentrationis 1000 for differentiation and 1001 for simulation and theaverage accuracy parameter for the (BH
4
minus
+ BO2
minus
) total is1008 for differentiation and 1004 for simulation (Table 3)
The feature of titration of alkaline-carbonate solutionsis the existence of three leaps on the titration curve(Figure 1(b))The first leap belongs to alkali while the secondand third ones are due to carbonates Correspondingly whenthe quantities of components are determined by the locationof peaks on the differential curve the quantity of CO
3
2minus isincluded twiceThe analysis of carbonate bymeans of the sec-ond peak gives a worse result than by the third one At a verysmall content of carbonate the second peak is not detectedThe average ldquomeasuredweightedrdquo value is 1215 for CO
3
2minus
ions by the second peak on the differential curve and 1115in the case of the third peak and the ldquomeasuredweightedrdquovalue is 1089 for the method of simulation The results ofcontrol determination of the alkali and carbonate contents inthe reference solutions OHminus + CO
3
2minus are shown in Figures3(c) and 3(d) for the two methods as the dependence ofthe accuracy parameter on the anionic fractions 120596
119894
In allcases the points of differentiation are more distant fromthe ldquocorrectrdquo level than those of simulation Consequentlythe method of simulation gives more correct results for theOHminus + CO
3
2minus system while the method of determinationcannot be recommended because of its high systematic errorsin carbonate analysis
The systematic error naturally increases with decreasingfractions of the analyzed ions In Figure 3(c) the trend ofsystematic errors is shown by means of solid lines for the
Journal of Fuels 7
Table 3 Average values of the ldquomeasuredweightedrdquo ratios for each ion in the mixture before and after correction of systematic errors
System Ions Method ldquoMeasuredweightedrdquo ratioBefore correction After correction
OHminus + BH4
minus + BO2
minus
OHminus Differentiation 0959 1000Simulation 0956 1001
BH4
minus + BO2
minus
Differentiation 1023 1008Simulation 1012 1004
OHminus + CO3
2minus
OHminus Simulation 0985 1003CO3
2minus Simulation 1089 0996
OHminus + BH4
minus + BO2
minus + CO3
2minus
OHminus Simulation 0874 0958BH4
minus + BO2
minus Simulation 1040 0992CO3
2minus Simulation 0934 1008
08
09
1
11
12
13
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ BH4
minus+ BO2
minus
OHminus simulationBH4
minus+ BO2
minus simulationNormOHminus differentiationBH4
minus+ BO2
minus differentiation
(a)
08
09
1
11
12
13
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ BH4
minus+ BO2
minus
OHminus simulationBH4
minus+ BO2
minus simulation + correctionNormOHminus differentiation + correctionBH4
minus+ BO2
minus differentiation + correction
(b)
05060708091
1112131415
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ CO3
2minus
OHminus simulation
NormCO3
2minus simulation
(c)
07
08
09
1
11
12
13
14
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ CO3
2minus
simulation + correctionOHminus
Normsimulation + correctionCO3
2minus
(d)
0
02
04
06
08
1
12
14
0 02 04 06 08 1
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
OHminus simulationBH4
minus+ BO2
minus simulationNormOHminus differentiation
CO32minus simulation
CO32minus differentiation
120596i
Measuredweighted
BH4minus+ BO2
minus+ CO3
2minus differentiation
(e)
Measuredweighted
02
04
06
08
1
12
14
0 02 04 06 08 1120596i
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
BH4minus+ BO2
minus simulation + correctionOHminus simulation + correction
Normsimulation + correctionCO3
2minus
(f)
Figure 3 Dependence of the ldquomeasuredweightedrdquo ratios for anions on their mole fraction 120596119894
in the mixture (a) for the OHminus + BH4
minus
+
BO2
minus system before correction of systematic errors (b) for the OHminus + BH4
minus
+ BO2
minus system after correction of systematic errors (c) for theOHminus +CO
3
2minus system before correction of systematic errors (d) for the OHminus +CO3
2minus system after correction of systematic errors (e) for theOHminus + BH
4
minus
+ BO2
minus
+CO3
2minus system before correction of systematic errors (f) for the OHminus + BH4
minus
+ BO2
minus
+CO3
2minus system after correctionof systematic errors The solid lines show the average trend of errors The dotted lines show the error interval for the method of simulation
8 Journal of Fuels
method of simulation The following equations have beensuggested for compensation of this trend
120573OHminus = [29 minus 19120596minus0055
OHminus ]minus1
120573CO3
2minus = [75120596minus001
CO3
2minus minus 65]minus1
(24)
After analysis and the determination of the 119899OHminus and 119899CO3
2minus
values a correction procedure is carried out by formula(24) Figure 3(d) shows the result of such correction Thesystematic error is completely compensated (Table 3) Allpoints lie within the ldquomeasuredweightedrdquo range 095ndash105for the anionic fractions within 04 lt 120596
119894
lt 1 that is therandom error does not exceed 5 and the random scatteringdoes not exceed 12 when 015 lt 120596
119894
lt 04 If the fractionof carbonate is less than 015 the reliability of its analysisdecreases because of the high random dispersion thereforeit is required to increase the number of replicate samplesThedirect titrimetric analysis of carbonate becomes impossiblewhen 120596CO
3
2minus lt 0015A feature of titration of alkaline-borohydride-borate-
carbonate solutions is the existence of three weak leaps onthe titration curve (Figure 1(d)) The first leap belongs toalkali while the second belongs to the ldquoBH
4
minus
+ BO2
minus
+
CO3
2minusrdquo total and the third one belongs to carbonate ionsRespectively at the quantification of components by meansof the position of peaks on the differential curve the totalcontent of boron 119899BH
4
minus+BO2
minus can be only calculated after thedetermination and extraction of the carbonate quantity
The results of our control determination of the anioncontents in the OHminus + BH
4
minus
+ BO2
minus
+ CO3
2minus mixturesby both methods are shown in Figure 3(e) The methodof differentiation gives an unsatisfactory result for car-bonate underestimating its content significantly the meanldquomeasuredweightedrdquo value being 0615 The carbonate peakdisappears when 120596CO
3
2minus lt 015 which leads to incorrectdetermination of the BH
4
minus
+ BO2
minus total Therefore for theOHminus+ BH
4
minus
+ BO2
minus
+ CO3
2minus system (the highly carbonatedand discharged fuel) the method of differentiation cannotbe recommended because of its large systematic errors incarbonate analysis and the method of simulation is onlysuggested for use The mean ldquomeasuredweightedrdquo values areshown in Table 3 The determination accuracy is 0874 forOHminus ions 1040 for the BH
4
minus
+ BO2
minus total and 0934 forCO3
2minus ions After correction these parameters become 09580992 and 1008 respectively The correcting coefficients are
120573OHminus = [198 minus 120596minus005
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [120596minus0085
BH4
minus+BO2
minus minus 003]minus1
120573CO3
2minus = [195 minus 120596minus001
CO3
2minus]minus1
(25)
The systematic error is thus compensated however therandom scattering of the points is higher than with moresimple options The random dispersion for alkali and borondoes not exceed 15 (all points arewithin 085ndash115) howeverit is only fair for carbonatewhen120596CO
3
2minus gt 01 If the carbonate
content is less than 01 its semiquantitative analysis is onlypossible But very small amounts of carbonate will not affectthe functioning of DBFC and only higher concentrations ofcarbonate exceeding the solubility limit can be deposited inthe electrode to hinder the functioning of DBFC
4 Conclusions
Theanalytic technique presented in our paper includes takinga small fuel sample from DBFC and performing two types oftitrations (acid-base and iodometric ones) which supplementeach otherThenecessity of exactly two techniques of titrationis due to the fact that iodometric titration determines theBH4
minus quantity in the sample only while the quantities ofother fuel components are provided by acid-base titration(OHminus BO
2
minus CO3
2minus)Therefore the joint application of thesetitration techniques allows one to most fully quantify thecurrent state of fuel in the process of DBFC functioningThe determination correctness of the technique has beenshown on artificial mixtures with a wide variation of theircomposition The average error depends on the number ofcomponents and their ratio in the mixture The investigationresults show that in the most complex case of highly carbon-ated and discharged fuel the maximal error of determinationdoes not exceed 15
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgment
The authors would like to gratefully acknowledge the RussianFoundation for Basic Research for financial support (Projectno 12-03-31802)
References
[1] J B Lakeman A Rose K D Pointon et al ldquoThe directborohydride fuel cell for UUV propulsion powerrdquo Journal ofPower Sources vol 162 no 2 pp 765ndash772 2006
[2] C P de Leon F C Walsh D Pletcher D J Browning and JB Lakeman ldquoDirect borohydride fuel cellsrdquo Journal of PowerSources vol 155 no 2 pp 172ndash181 2006
[3] R Aiello J H Sharp and M A Matthews ldquoProduction ofhydrogen from chemical hydrides via hydrolysis with steamrdquoInternational Journal of Hydrogen Energy vol 24 no 12 pp1123ndash1130 1999
[4] S C Amendola S L Sharp-Goldman M S Janjua et al ldquoSafeportable hydrogen gas generator using aqueous borohydridesolution and Ru catalystrdquo International Journal of HydrogenEnergy vol 25 no 10 pp 969ndash975 2000
[5] H I Schlesinger H C Brown A E Finholt J R GilbreathH R Hoekstra and E K Hyde ldquoSodium borohydride itshydrolysis and its use as a reducing agent and in the generationof hydrogenrdquo Journal of the American Chemical Society vol 75no 1 pp 215ndash219 1953
Journal of Fuels 9
[6] S C Amendola P Onnerud M T Kelly P J Petillo S LSharp-Goldman and M Binder ldquoNovel high power densityborohydride-air cellrdquo Journal of Power Sources vol 84 no 1 pp130ndash133 1999
[7] B H Liu and Z P Li ldquoCurrent status and progress of directborohydride fuel cell technology developmentrdquo Journal ofPower Sources vol 187 no 2 pp 291ndash297 2009
[8] B H Liu and Z P Li ldquoA review hydrogen generation fromborohydride hydrolysis reactionrdquo Journal of Power Sources vol187 no 2 pp 527ndash534 2009
[9] B Weng Z Wu Z Li H Yang and H Leng ldquoHydrogengeneration from noncatalytic hydrolysis of LiBH4NH3BH3mixture for fuel cell applicationsrdquo International Journal ofHydrogen Energy vol 36 no 17 pp 10870ndash10876 2011
[10] A E Sanli I Kayacan B Z Uysal and M L Aksu ldquoRecoveryof borohydride from metaborate solution using a silver catalystfor application of direct rechargable borohydrideperoxide fuelcellsrdquo Journal of Power Sources vol 195 no 9 pp 2604ndash26072010
[11] R Jamard J Salomon A Martinent-Beaumont and CCoutanceau ldquoLife time test in direct borohydride fuel cellsystemrdquo Journal of Power Sources vol 193 no 2 pp 779ndash7872009
[12] J-H Wee ldquoA comparison of sodium borohydride as a fuel forproton exchange membrane fuel cells and for direct borohy-dride fuel cellsrdquo Journal of Power Sources vol 155 no 2 pp329ndash339 2006
[13] A V Churikov K V Zapsis V V Khramkov M A ChurikovM P Smotrov and I A Kazarinov ldquoPhase diagrams of theternary systems NaBH
4
+ NaOH + H2
O KBH4
+ KOH + H2
ONaBO
2
+ NaOH + H2
O and KBO2
+ KOH + H2
O at minus10∘CrdquoJournal of Chemical and Engineering Data vol 56 no 1 pp 9ndash13 2011
[14] A V Churikov K V Zapsis V V Khramkov M A Churikovand I M Gamayunova ldquoTemperature-induced transformationof the phase diagrams of ternary systems NaBO
2
+ NaOH+ H2
O and KBO2
+ KOH + H2
Ordquo Journal of Chemical andEngineering Data vol 56 no 3 pp 383ndash389 2011
[15] A V Churikov K V Zapsis A V Ivanishchev and V OSychova ldquoTemperature-induced transformation of the phasediagrams of ternary systems NaBH
4
+ NaOH +H2
O and KBH4
+ KOH + H2
Ordquo Journal of Chemical and Engineering Data vol56 no 5 pp 2543ndash2552 2011
[16] G Rostamikiaa and M J Janik ldquoDirect borohydride oxidationmechanism determination and design of alloy catalysts guidedby density functional theoryrdquo Energy amp Environmental Sciencevol 3 pp 1262ndash1274 2010
[17] B Sljuki J Miliki D M F Santosa and C A C SequeiraldquoCarbon-supported Pt
075
M025
(M = Ni or Co) electrocatalystsfor borohydride oxidationrdquo Electrochim Acta vol 107 pp 577ndash583 2013
[18] B H Liu J Q Yang and Z P Li ldquoConcentration ratio of[OHminus][BH
4
minus] a controlling factor for the fuel efficiency ofborohydride electro-oxidationrdquo International Journal of Hydro-gen Energy vol 34 no 23 pp 9436ndash9443 2009
[19] A V Churikov A V Ivanishchev I M Gamayunova andA V Ushakov ldquoDensity calculations for (Na K)BH
4
+ (NaK)BO
2
+ (Na K)OH + H2
O solutions used in hydrogen powerengineeringrdquo Journal of Chemical and Engineering Data vol 56no 11 pp 3984ndash3993 2011
[20] A V Churikov V O Romanova M A Churikov and I MGamayunova ldquoThemodel of fuel transformation at discharge of
direct borohydride fuel cellrdquo International Review of ChemicalEngineering vol 4 pp 263ndash268 2012
[21] A V Churikov I M Gamayunova K V Zapsis M AChurikov and A V Ivanishchev ldquoInfluence of temperature andalkalinity on the hydrolysis rate of borohydride ions in aqueoussolutionrdquo International Journal of Hydrogen Energy vol 37 no1 pp 335ndash344 2012
[22] Z P Li B H Liu K Arai and S Suda ldquoA fuel cell developmentfor using borohydrides as the fuelrdquo Journal of the Electrochemi-cal Society vol 150 no 7 pp A868ndashA872 2003
[23] Y Wang P Hea and H Zhou ldquoA novel direct borohydridefuel cell using an acid-alkaline hybrid electrolyterdquo Energy ampEnvironmental Science vol 3 no 10 pp 1515ndash1518 2010
[24] J Ma N A Choudhury and Y Sahai ldquoA comprehensive reviewof direct borohydride fuel cellsrdquo Renewable and SustainableEnergy Reviews vol 14 no 1 pp 183ndash199 2010
[25] R Bruhlmann and L Piatti ldquoAn improved method for thetitrimetric determination of boron in ironrdquo Chimia vol 11 p203 1957
[26] A Keshan and C Bimba ldquoCobalt-potassium and ammonium-cobalt dodecaboraterdquo Izvestiya Akademii Nauk Latvijskoj SSRp 115 1954
[27] J Czakow T Steciak and O Szczebinska ldquoThe spectral deter-mination of trace amounts of impurities in the solutions withthe metal electrodes in the spark moderdquo Analytical Chemistryvol 3 p 745 1958
[28] R Rosotti ldquoA fast method for the determination of traceamounts of boron in the steelrdquo Analytical Chemistry vol 44 p208 1962
[29] J Varka and A Sklaf ldquoApplication of potentiometric titrationIV Determination of B
2
O3
in glass enamels and boron-containing raw materialsrdquo Keramik vol 7 p 12 1957
[30] D E Williams and J Vilamis ldquoStability of the curcumincomplex in boron determinationrdquoAnalytical Chemistry vol 33pp 1098ndash1100 1961
[31] S Kertes and M Lederer ldquoPaper chromatography of inorganicions Rf values in mixtures of butanol and Hbrrdquo AnalyticaChimica Acta vol 15 no C pp 543ndash547 1956
[32] A A Nemodruk and Z K Karalova The Analytical Chemistryof Boron Nauka 1964
[33] C A Parker ldquoRaman spectra in spectrofluorimetryrdquo The Ana-lyst vol 84 no 1000 pp 446ndash453 1959
[34] C A Parker and W J Barnes ldquoFluorimetric determination ofboron application to silicon sea water and steelrdquo The Analystvol 85 no 1016 pp 828ndash838 1960
[35] M V Akhmanova Methods of Determination and Analysis ofRear Elements Izdat Akademija Nauk SSSR 1961
[36] E H Jensen A Study on Sodium Borohydride Nyt NordiskForlag Amold Busck Copenhagen Denmark 1954
[37] I Fatt and M Tashima Alkali Metal Dispersions D VanNostrand Co Inc Princeton NJ USA 1961
[38] DA Lyttle EH Jensen andWA Struck ldquoA simple volumetricassay for sodium borohydriderdquo Analytical Chemistry vol 24no 11 pp 1843ndash1844 1952
[39] P K Norkus ldquoIodometric determination of borohydriderdquoRussian Journal of Analytical Chemistry vol 23 pp 908ndash9111968
[40] N N Malrsquoceva and V S Khain Sodium Borohydride Propertiesand Application Nauka 1985
10 Journal of Fuels
[41] C Harzdorf and O Steinhauser ldquoZur photometrisehen Titra-tion von Fluorid mit Thoriumnitratrdquo Freseniusrsquo Zeitschrift furAnalytische Chemie vol 210 no 2 pp 106ndash112 1965
[42] W D Davis L S Mason and G Stegeman ldquoThe heats offormation of sodium borohydride lithium borohydride andlithium aluminum hydriderdquo Journal of the American ChemicalSociety vol 71 no 8 pp 2775ndash2781 1949
[43] S W Chaikin ldquoDirect volumetric assay of sodium borohydrideand potassium borohydriderdquo Analytical Chemistry vol 25 no5 pp 831ndash832 1953
[44] U Ulku and G Somer ldquoDetermination of trace borohydride inbasic solutions using differential pulse polarographyrdquo TurkishJournal of Chemistry vol 33 pp 657ndash665 2009
[45] H Celikkan H Aydin and M L Aksu ldquoThe electroanalyticaldetermination of sodium borohydride using a gold electroderdquoTurkish Journal of Chemistry vol 29 pp 519ndash524 2005
[46] M V Mirkin and A J Bard ldquoVoltammetric method forthe determination of borohydride concentration in alkalineaqueous solutionsrdquoAnalytical Chemistry vol 63 no 5 pp 532ndash533 1991
[47] D M F Santos and C A C Sequeira ldquoPotentiometric moni-toring of sodium borohydride in aqueous solutionsrdquo Ciencia sTecnologia dos Materials vol 20 no 3-4 pp 31ndash34 2008
[48] D M F Santos and C A C Sequeira ldquoSodium borohydridedetermination by measurement of open circuit potentialsrdquoJournal of Electroanalytical Chemistry vol 627 pp 1ndash8 2009
[49] H C Brown and A C Boyd Jr ldquoArgentimetric procedure forborohydride determinationrdquo Analytical Chemistry vol 27 no1 pp 156ndash158 1955
[50] V B Breicis A O Berzina and L K Lepin ldquoPotentiomet-ric titration of water solutions of sodium borohydride byhydrochloric acidrdquo Scientific Short Letter of Riga PolytechnicInstitute vol 15 pp 179ndash188 19651966
[51] U U Lurie Handbook on Analytical Chemistry Khimiya 1979[52] R A Lidin L L Andreeva and V A Molochko Hand-
book of Inorganic Chemistry Constants of Inorganic SubstancesKhimiya 1987
[53] R A Robinson and R H Stokes Electrolyte Solutions the Mea-surement and Interpretation of Conductance Chemical Potentialand Diffusion in Solutions of Simple Electrolytes ButterworthsLondon UK 1959
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
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FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
StructuresJournal of
International Journal of
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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
EnergyJournal of
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Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
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Wind EnergyJournal of
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Nuclear EnergyInternational Journal of
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High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Journal of Fuels 5
0
2
4
6
8
10
12
14
0 4 8 12
pH
ExperimentCalculationDifferentiation
Vt (mL)
minus100
900
1900
2900
3900
4900
dpH
dVt
OH minus
(a)
0
20
40
60
80
100
120
0
2
4
6
8
10
12
14
0 2 4 6 8 10 12 14
pH
ExperimentCalculationDifferentiation
Vt (mL)
dpH
dVt
OHminus+ CO3
2minus
(b)
0
20
40
60
80
100
120
0
4
8
12
16
0 1 2 3 4 5 6
pH
ExperimentCalculationDifferentiation
Vt (mL)
dpH
dVt
OHminus+ BH4
minus+ BO2
minus
(c)
20
0
40
60
80
100
120
0
2
4
6
8
10
12
14
0 2 4 6 8
pH
ExperimentCalculationDifferentiation
Vt (mL)
dpH
dVt
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
(d)
Figure 1 Calculated titration curves experimental titration curves and the corresponding 119889pH119889119881119905
versus 119881119905
curves for aqueous solutionsof several mixtures of anions (a) OHminus (b) OHminus + CO
3
2minus (c) OHminus + BH4
minus or OHminus + BO2
minus or OHminus + BH4
minus
+ BO2
minus (d) OHminus + BH4
minus
+
BO2
minus
+ CO3
minus
pH versus 119881calc one The variable parameters are the soughtquantities of components in the aliquot 119899OHminus 119899BH
4
minus+BO2
minus and119899CO3
2minus The criterion of optimum is the minimum dispersion
1198782
=sum119870
119896=1
(pH119896
minus pHcalc119896)2
119870 minus 1
=sum119870
119896=1
((119889pH119889119881119905119896
) (119881119905119896
minus 119881calc119896))2
119870 minus 1
(20)
Here119870 is the number of points on the titration curve Figure 1shows the experimental and calculated titration curves forfew solutions of various multicomponent mixtures It is
visible that the applied computational methods allow exactsimulating experimental curves
Error Analysis and Estimation of AccuracyAnumber of refer-ence solutions of a desired composition were prepared usingKBO2
NaBH4
KBH4
NaOHKOHNa2
CO3
andK2
CO3
forvalidation of our analytical methodology (the concentrationranges of each analyzed ion in the considered samples arepresented in Table 2) In order to detect systematic errorsthe dependences of the ldquomeasuredweightedrdquo ratios on theanionic fraction 120596
119894
were plotted (120596119894
is the mole fraction ofthe 119894th anion in the total amount of the analyzed anions 120596varies from 0 up to 1) The results are given in Figure 3 Theaverage value of the ldquomeasuredweightedrdquo ratio for each ionis presented in Table 3
6 Journal of Fuels
Table 2 Considered concentration ranges of analyzed ions in thesample
Ion Concentration range in the analyzed sample molsdotLminus1
OHminus 002ndash12BH4
minus 002ndash02BO2
minus 005ndash02CO3
2minus 0008ndash01
It is apparent from Table 3 that the simulation methodalso gives a systematic error The causes can be simplificationof the theory the impossibility to consider all side processesthe inability to exactly calculate activity coefficients and soforth so the shape of the calculated curve may not com-pletely coincide with the experimental curve In particularin the titration process of borate solutions the formationof poliborates and their hydrated forms is possible In thecase of simulation the lower branch of the titration curveshould be limitedwhen all equivalence points are passed overAccelerated titration or cold solutionmay cause an additionalerror due to the inhibition of reaction (6) and the failure ofchemical equilibrium
The concentration of OHminus ions is estimated with an accu-racy of 0959 and 0956 for the differentiation and simulationmethods respectivelyThe total of (BH
4
minus
+BO2
minus) is estimatedwith an accuracy of 1023 and 1012 for the differentiationand simulation methods respectively (Table 3) Thus for theOHminus+BH
4
minus
+BO2
minus system the differentiation and simulationmethods give similar results and have no advantages overeach other and the systematic error is small but naturallyincreases with decreasing share of the analyzed ionThe trendof the systematic error is shown in Figure 3(a) by means ofsolid lines Both methods overestimate the content of boronin the sample and underestimate the content of alkali Forcompensation of the systematic error the following equationshave been obtained for the method of differentiation
120573OHminus = [138 minus 04120596minus005
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [120596minus005
BH4
minus+BO2
minus minus 0025]minus1
(21)
and for the method of simulation
120573OHminus = [139 minus 04120596minus008
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [07120596minus005
BH4
minus+BO2
minus + 028]minus1
(22)
After analysis and the determination of the components119899OHminus and 119899BH
4
minus+BO2
minus a correction procedure was carried outby multiplying the values 119899
119894
found by the correspondingcorrection coefficients 120573
119894
calculated from formulae (21) or(22) Finally the corrected amounts of the 119894th component inthe sample 119899
119894cor are
119899119894cor = 120573119894119899119894 (23)
Figure 3(b) shows the result of correction of the data given inFigure 3(a)The systematic error was totally compensated forall the variants of analysis (Table 3)
0 2 4 6 8 10Vt (mL)
minus600
minus200
200
600
1000
E(m
V)
Vlowastt
minus27000
minus18000
minus9000
0
9000
dEdVt
Figure 2 Curve of direct iodometric titration of borohydride ionsin an aqueous solution with the mixture of anions OHminus + BH
4
minus
+
BO2
minus
+ CO3
2minus (119881lowast119905
is equivalence point)
When the value of the anionic fraction 04 lt 120596119894
lt 1 allpoints lie within the ldquomeasuredweightedrdquo range 095ndash105that is the random error does not exceed 5 all points liewithin the range 088ndash112 when 005 lt 120596
119894
lt 04 that isthe random error does not exceed 12 It is only possibleto perform semiquantitative analysis of any component at itsvery small content in the mixture (120596
119894
lt 002) On correctionthe average accuracy parameter of the OHminus concentrationis 1000 for differentiation and 1001 for simulation and theaverage accuracy parameter for the (BH
4
minus
+ BO2
minus
) total is1008 for differentiation and 1004 for simulation (Table 3)
The feature of titration of alkaline-carbonate solutionsis the existence of three leaps on the titration curve(Figure 1(b))The first leap belongs to alkali while the secondand third ones are due to carbonates Correspondingly whenthe quantities of components are determined by the locationof peaks on the differential curve the quantity of CO
3
2minus isincluded twiceThe analysis of carbonate bymeans of the sec-ond peak gives a worse result than by the third one At a verysmall content of carbonate the second peak is not detectedThe average ldquomeasuredweightedrdquo value is 1215 for CO
3
2minus
ions by the second peak on the differential curve and 1115in the case of the third peak and the ldquomeasuredweightedrdquovalue is 1089 for the method of simulation The results ofcontrol determination of the alkali and carbonate contents inthe reference solutions OHminus + CO
3
2minus are shown in Figures3(c) and 3(d) for the two methods as the dependence ofthe accuracy parameter on the anionic fractions 120596
119894
In allcases the points of differentiation are more distant fromthe ldquocorrectrdquo level than those of simulation Consequentlythe method of simulation gives more correct results for theOHminus + CO
3
2minus system while the method of determinationcannot be recommended because of its high systematic errorsin carbonate analysis
The systematic error naturally increases with decreasingfractions of the analyzed ions In Figure 3(c) the trend ofsystematic errors is shown by means of solid lines for the
Journal of Fuels 7
Table 3 Average values of the ldquomeasuredweightedrdquo ratios for each ion in the mixture before and after correction of systematic errors
System Ions Method ldquoMeasuredweightedrdquo ratioBefore correction After correction
OHminus + BH4
minus + BO2
minus
OHminus Differentiation 0959 1000Simulation 0956 1001
BH4
minus + BO2
minus
Differentiation 1023 1008Simulation 1012 1004
OHminus + CO3
2minus
OHminus Simulation 0985 1003CO3
2minus Simulation 1089 0996
OHminus + BH4
minus + BO2
minus + CO3
2minus
OHminus Simulation 0874 0958BH4
minus + BO2
minus Simulation 1040 0992CO3
2minus Simulation 0934 1008
08
09
1
11
12
13
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ BH4
minus+ BO2
minus
OHminus simulationBH4
minus+ BO2
minus simulationNormOHminus differentiationBH4
minus+ BO2
minus differentiation
(a)
08
09
1
11
12
13
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ BH4
minus+ BO2
minus
OHminus simulationBH4
minus+ BO2
minus simulation + correctionNormOHminus differentiation + correctionBH4
minus+ BO2
minus differentiation + correction
(b)
05060708091
1112131415
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ CO3
2minus
OHminus simulation
NormCO3
2minus simulation
(c)
07
08
09
1
11
12
13
14
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ CO3
2minus
simulation + correctionOHminus
Normsimulation + correctionCO3
2minus
(d)
0
02
04
06
08
1
12
14
0 02 04 06 08 1
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
OHminus simulationBH4
minus+ BO2
minus simulationNormOHminus differentiation
CO32minus simulation
CO32minus differentiation
120596i
Measuredweighted
BH4minus+ BO2
minus+ CO3
2minus differentiation
(e)
Measuredweighted
02
04
06
08
1
12
14
0 02 04 06 08 1120596i
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
BH4minus+ BO2
minus simulation + correctionOHminus simulation + correction
Normsimulation + correctionCO3
2minus
(f)
Figure 3 Dependence of the ldquomeasuredweightedrdquo ratios for anions on their mole fraction 120596119894
in the mixture (a) for the OHminus + BH4
minus
+
BO2
minus system before correction of systematic errors (b) for the OHminus + BH4
minus
+ BO2
minus system after correction of systematic errors (c) for theOHminus +CO
3
2minus system before correction of systematic errors (d) for the OHminus +CO3
2minus system after correction of systematic errors (e) for theOHminus + BH
4
minus
+ BO2
minus
+CO3
2minus system before correction of systematic errors (f) for the OHminus + BH4
minus
+ BO2
minus
+CO3
2minus system after correctionof systematic errors The solid lines show the average trend of errors The dotted lines show the error interval for the method of simulation
8 Journal of Fuels
method of simulation The following equations have beensuggested for compensation of this trend
120573OHminus = [29 minus 19120596minus0055
OHminus ]minus1
120573CO3
2minus = [75120596minus001
CO3
2minus minus 65]minus1
(24)
After analysis and the determination of the 119899OHminus and 119899CO3
2minus
values a correction procedure is carried out by formula(24) Figure 3(d) shows the result of such correction Thesystematic error is completely compensated (Table 3) Allpoints lie within the ldquomeasuredweightedrdquo range 095ndash105for the anionic fractions within 04 lt 120596
119894
lt 1 that is therandom error does not exceed 5 and the random scatteringdoes not exceed 12 when 015 lt 120596
119894
lt 04 If the fractionof carbonate is less than 015 the reliability of its analysisdecreases because of the high random dispersion thereforeit is required to increase the number of replicate samplesThedirect titrimetric analysis of carbonate becomes impossiblewhen 120596CO
3
2minus lt 0015A feature of titration of alkaline-borohydride-borate-
carbonate solutions is the existence of three weak leaps onthe titration curve (Figure 1(d)) The first leap belongs toalkali while the second belongs to the ldquoBH
4
minus
+ BO2
minus
+
CO3
2minusrdquo total and the third one belongs to carbonate ionsRespectively at the quantification of components by meansof the position of peaks on the differential curve the totalcontent of boron 119899BH
4
minus+BO2
minus can be only calculated after thedetermination and extraction of the carbonate quantity
The results of our control determination of the anioncontents in the OHminus + BH
4
minus
+ BO2
minus
+ CO3
2minus mixturesby both methods are shown in Figure 3(e) The methodof differentiation gives an unsatisfactory result for car-bonate underestimating its content significantly the meanldquomeasuredweightedrdquo value being 0615 The carbonate peakdisappears when 120596CO
3
2minus lt 015 which leads to incorrectdetermination of the BH
4
minus
+ BO2
minus total Therefore for theOHminus+ BH
4
minus
+ BO2
minus
+ CO3
2minus system (the highly carbonatedand discharged fuel) the method of differentiation cannotbe recommended because of its large systematic errors incarbonate analysis and the method of simulation is onlysuggested for use The mean ldquomeasuredweightedrdquo values areshown in Table 3 The determination accuracy is 0874 forOHminus ions 1040 for the BH
4
minus
+ BO2
minus total and 0934 forCO3
2minus ions After correction these parameters become 09580992 and 1008 respectively The correcting coefficients are
120573OHminus = [198 minus 120596minus005
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [120596minus0085
BH4
minus+BO2
minus minus 003]minus1
120573CO3
2minus = [195 minus 120596minus001
CO3
2minus]minus1
(25)
The systematic error is thus compensated however therandom scattering of the points is higher than with moresimple options The random dispersion for alkali and borondoes not exceed 15 (all points arewithin 085ndash115) howeverit is only fair for carbonatewhen120596CO
3
2minus gt 01 If the carbonate
content is less than 01 its semiquantitative analysis is onlypossible But very small amounts of carbonate will not affectthe functioning of DBFC and only higher concentrations ofcarbonate exceeding the solubility limit can be deposited inthe electrode to hinder the functioning of DBFC
4 Conclusions
Theanalytic technique presented in our paper includes takinga small fuel sample from DBFC and performing two types oftitrations (acid-base and iodometric ones) which supplementeach otherThenecessity of exactly two techniques of titrationis due to the fact that iodometric titration determines theBH4
minus quantity in the sample only while the quantities ofother fuel components are provided by acid-base titration(OHminus BO
2
minus CO3
2minus)Therefore the joint application of thesetitration techniques allows one to most fully quantify thecurrent state of fuel in the process of DBFC functioningThe determination correctness of the technique has beenshown on artificial mixtures with a wide variation of theircomposition The average error depends on the number ofcomponents and their ratio in the mixture The investigationresults show that in the most complex case of highly carbon-ated and discharged fuel the maximal error of determinationdoes not exceed 15
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgment
The authors would like to gratefully acknowledge the RussianFoundation for Basic Research for financial support (Projectno 12-03-31802)
References
[1] J B Lakeman A Rose K D Pointon et al ldquoThe directborohydride fuel cell for UUV propulsion powerrdquo Journal ofPower Sources vol 162 no 2 pp 765ndash772 2006
[2] C P de Leon F C Walsh D Pletcher D J Browning and JB Lakeman ldquoDirect borohydride fuel cellsrdquo Journal of PowerSources vol 155 no 2 pp 172ndash181 2006
[3] R Aiello J H Sharp and M A Matthews ldquoProduction ofhydrogen from chemical hydrides via hydrolysis with steamrdquoInternational Journal of Hydrogen Energy vol 24 no 12 pp1123ndash1130 1999
[4] S C Amendola S L Sharp-Goldman M S Janjua et al ldquoSafeportable hydrogen gas generator using aqueous borohydridesolution and Ru catalystrdquo International Journal of HydrogenEnergy vol 25 no 10 pp 969ndash975 2000
[5] H I Schlesinger H C Brown A E Finholt J R GilbreathH R Hoekstra and E K Hyde ldquoSodium borohydride itshydrolysis and its use as a reducing agent and in the generationof hydrogenrdquo Journal of the American Chemical Society vol 75no 1 pp 215ndash219 1953
Journal of Fuels 9
[6] S C Amendola P Onnerud M T Kelly P J Petillo S LSharp-Goldman and M Binder ldquoNovel high power densityborohydride-air cellrdquo Journal of Power Sources vol 84 no 1 pp130ndash133 1999
[7] B H Liu and Z P Li ldquoCurrent status and progress of directborohydride fuel cell technology developmentrdquo Journal ofPower Sources vol 187 no 2 pp 291ndash297 2009
[8] B H Liu and Z P Li ldquoA review hydrogen generation fromborohydride hydrolysis reactionrdquo Journal of Power Sources vol187 no 2 pp 527ndash534 2009
[9] B Weng Z Wu Z Li H Yang and H Leng ldquoHydrogengeneration from noncatalytic hydrolysis of LiBH4NH3BH3mixture for fuel cell applicationsrdquo International Journal ofHydrogen Energy vol 36 no 17 pp 10870ndash10876 2011
[10] A E Sanli I Kayacan B Z Uysal and M L Aksu ldquoRecoveryof borohydride from metaborate solution using a silver catalystfor application of direct rechargable borohydrideperoxide fuelcellsrdquo Journal of Power Sources vol 195 no 9 pp 2604ndash26072010
[11] R Jamard J Salomon A Martinent-Beaumont and CCoutanceau ldquoLife time test in direct borohydride fuel cellsystemrdquo Journal of Power Sources vol 193 no 2 pp 779ndash7872009
[12] J-H Wee ldquoA comparison of sodium borohydride as a fuel forproton exchange membrane fuel cells and for direct borohy-dride fuel cellsrdquo Journal of Power Sources vol 155 no 2 pp329ndash339 2006
[13] A V Churikov K V Zapsis V V Khramkov M A ChurikovM P Smotrov and I A Kazarinov ldquoPhase diagrams of theternary systems NaBH
4
+ NaOH + H2
O KBH4
+ KOH + H2
ONaBO
2
+ NaOH + H2
O and KBO2
+ KOH + H2
O at minus10∘CrdquoJournal of Chemical and Engineering Data vol 56 no 1 pp 9ndash13 2011
[14] A V Churikov K V Zapsis V V Khramkov M A Churikovand I M Gamayunova ldquoTemperature-induced transformationof the phase diagrams of ternary systems NaBO
2
+ NaOH+ H2
O and KBO2
+ KOH + H2
Ordquo Journal of Chemical andEngineering Data vol 56 no 3 pp 383ndash389 2011
[15] A V Churikov K V Zapsis A V Ivanishchev and V OSychova ldquoTemperature-induced transformation of the phasediagrams of ternary systems NaBH
4
+ NaOH +H2
O and KBH4
+ KOH + H2
Ordquo Journal of Chemical and Engineering Data vol56 no 5 pp 2543ndash2552 2011
[16] G Rostamikiaa and M J Janik ldquoDirect borohydride oxidationmechanism determination and design of alloy catalysts guidedby density functional theoryrdquo Energy amp Environmental Sciencevol 3 pp 1262ndash1274 2010
[17] B Sljuki J Miliki D M F Santosa and C A C SequeiraldquoCarbon-supported Pt
075
M025
(M = Ni or Co) electrocatalystsfor borohydride oxidationrdquo Electrochim Acta vol 107 pp 577ndash583 2013
[18] B H Liu J Q Yang and Z P Li ldquoConcentration ratio of[OHminus][BH
4
minus] a controlling factor for the fuel efficiency ofborohydride electro-oxidationrdquo International Journal of Hydro-gen Energy vol 34 no 23 pp 9436ndash9443 2009
[19] A V Churikov A V Ivanishchev I M Gamayunova andA V Ushakov ldquoDensity calculations for (Na K)BH
4
+ (NaK)BO
2
+ (Na K)OH + H2
O solutions used in hydrogen powerengineeringrdquo Journal of Chemical and Engineering Data vol 56no 11 pp 3984ndash3993 2011
[20] A V Churikov V O Romanova M A Churikov and I MGamayunova ldquoThemodel of fuel transformation at discharge of
direct borohydride fuel cellrdquo International Review of ChemicalEngineering vol 4 pp 263ndash268 2012
[21] A V Churikov I M Gamayunova K V Zapsis M AChurikov and A V Ivanishchev ldquoInfluence of temperature andalkalinity on the hydrolysis rate of borohydride ions in aqueoussolutionrdquo International Journal of Hydrogen Energy vol 37 no1 pp 335ndash344 2012
[22] Z P Li B H Liu K Arai and S Suda ldquoA fuel cell developmentfor using borohydrides as the fuelrdquo Journal of the Electrochemi-cal Society vol 150 no 7 pp A868ndashA872 2003
[23] Y Wang P Hea and H Zhou ldquoA novel direct borohydridefuel cell using an acid-alkaline hybrid electrolyterdquo Energy ampEnvironmental Science vol 3 no 10 pp 1515ndash1518 2010
[24] J Ma N A Choudhury and Y Sahai ldquoA comprehensive reviewof direct borohydride fuel cellsrdquo Renewable and SustainableEnergy Reviews vol 14 no 1 pp 183ndash199 2010
[25] R Bruhlmann and L Piatti ldquoAn improved method for thetitrimetric determination of boron in ironrdquo Chimia vol 11 p203 1957
[26] A Keshan and C Bimba ldquoCobalt-potassium and ammonium-cobalt dodecaboraterdquo Izvestiya Akademii Nauk Latvijskoj SSRp 115 1954
[27] J Czakow T Steciak and O Szczebinska ldquoThe spectral deter-mination of trace amounts of impurities in the solutions withthe metal electrodes in the spark moderdquo Analytical Chemistryvol 3 p 745 1958
[28] R Rosotti ldquoA fast method for the determination of traceamounts of boron in the steelrdquo Analytical Chemistry vol 44 p208 1962
[29] J Varka and A Sklaf ldquoApplication of potentiometric titrationIV Determination of B
2
O3
in glass enamels and boron-containing raw materialsrdquo Keramik vol 7 p 12 1957
[30] D E Williams and J Vilamis ldquoStability of the curcumincomplex in boron determinationrdquoAnalytical Chemistry vol 33pp 1098ndash1100 1961
[31] S Kertes and M Lederer ldquoPaper chromatography of inorganicions Rf values in mixtures of butanol and Hbrrdquo AnalyticaChimica Acta vol 15 no C pp 543ndash547 1956
[32] A A Nemodruk and Z K Karalova The Analytical Chemistryof Boron Nauka 1964
[33] C A Parker ldquoRaman spectra in spectrofluorimetryrdquo The Ana-lyst vol 84 no 1000 pp 446ndash453 1959
[34] C A Parker and W J Barnes ldquoFluorimetric determination ofboron application to silicon sea water and steelrdquo The Analystvol 85 no 1016 pp 828ndash838 1960
[35] M V Akhmanova Methods of Determination and Analysis ofRear Elements Izdat Akademija Nauk SSSR 1961
[36] E H Jensen A Study on Sodium Borohydride Nyt NordiskForlag Amold Busck Copenhagen Denmark 1954
[37] I Fatt and M Tashima Alkali Metal Dispersions D VanNostrand Co Inc Princeton NJ USA 1961
[38] DA Lyttle EH Jensen andWA Struck ldquoA simple volumetricassay for sodium borohydriderdquo Analytical Chemistry vol 24no 11 pp 1843ndash1844 1952
[39] P K Norkus ldquoIodometric determination of borohydriderdquoRussian Journal of Analytical Chemistry vol 23 pp 908ndash9111968
[40] N N Malrsquoceva and V S Khain Sodium Borohydride Propertiesand Application Nauka 1985
10 Journal of Fuels
[41] C Harzdorf and O Steinhauser ldquoZur photometrisehen Titra-tion von Fluorid mit Thoriumnitratrdquo Freseniusrsquo Zeitschrift furAnalytische Chemie vol 210 no 2 pp 106ndash112 1965
[42] W D Davis L S Mason and G Stegeman ldquoThe heats offormation of sodium borohydride lithium borohydride andlithium aluminum hydriderdquo Journal of the American ChemicalSociety vol 71 no 8 pp 2775ndash2781 1949
[43] S W Chaikin ldquoDirect volumetric assay of sodium borohydrideand potassium borohydriderdquo Analytical Chemistry vol 25 no5 pp 831ndash832 1953
[44] U Ulku and G Somer ldquoDetermination of trace borohydride inbasic solutions using differential pulse polarographyrdquo TurkishJournal of Chemistry vol 33 pp 657ndash665 2009
[45] H Celikkan H Aydin and M L Aksu ldquoThe electroanalyticaldetermination of sodium borohydride using a gold electroderdquoTurkish Journal of Chemistry vol 29 pp 519ndash524 2005
[46] M V Mirkin and A J Bard ldquoVoltammetric method forthe determination of borohydride concentration in alkalineaqueous solutionsrdquoAnalytical Chemistry vol 63 no 5 pp 532ndash533 1991
[47] D M F Santos and C A C Sequeira ldquoPotentiometric moni-toring of sodium borohydride in aqueous solutionsrdquo Ciencia sTecnologia dos Materials vol 20 no 3-4 pp 31ndash34 2008
[48] D M F Santos and C A C Sequeira ldquoSodium borohydridedetermination by measurement of open circuit potentialsrdquoJournal of Electroanalytical Chemistry vol 627 pp 1ndash8 2009
[49] H C Brown and A C Boyd Jr ldquoArgentimetric procedure forborohydride determinationrdquo Analytical Chemistry vol 27 no1 pp 156ndash158 1955
[50] V B Breicis A O Berzina and L K Lepin ldquoPotentiomet-ric titration of water solutions of sodium borohydride byhydrochloric acidrdquo Scientific Short Letter of Riga PolytechnicInstitute vol 15 pp 179ndash188 19651966
[51] U U Lurie Handbook on Analytical Chemistry Khimiya 1979[52] R A Lidin L L Andreeva and V A Molochko Hand-
book of Inorganic Chemistry Constants of Inorganic SubstancesKhimiya 1987
[53] R A Robinson and R H Stokes Electrolyte Solutions the Mea-surement and Interpretation of Conductance Chemical Potentialand Diffusion in Solutions of Simple Electrolytes ButterworthsLondon UK 1959
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
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Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Journal ofEngineeringVolume 2014
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Wind EnergyJournal of
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Nuclear EnergyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
6 Journal of Fuels
Table 2 Considered concentration ranges of analyzed ions in thesample
Ion Concentration range in the analyzed sample molsdotLminus1
OHminus 002ndash12BH4
minus 002ndash02BO2
minus 005ndash02CO3
2minus 0008ndash01
It is apparent from Table 3 that the simulation methodalso gives a systematic error The causes can be simplificationof the theory the impossibility to consider all side processesthe inability to exactly calculate activity coefficients and soforth so the shape of the calculated curve may not com-pletely coincide with the experimental curve In particularin the titration process of borate solutions the formationof poliborates and their hydrated forms is possible In thecase of simulation the lower branch of the titration curveshould be limitedwhen all equivalence points are passed overAccelerated titration or cold solutionmay cause an additionalerror due to the inhibition of reaction (6) and the failure ofchemical equilibrium
The concentration of OHminus ions is estimated with an accu-racy of 0959 and 0956 for the differentiation and simulationmethods respectivelyThe total of (BH
4
minus
+BO2
minus) is estimatedwith an accuracy of 1023 and 1012 for the differentiationand simulation methods respectively (Table 3) Thus for theOHminus+BH
4
minus
+BO2
minus system the differentiation and simulationmethods give similar results and have no advantages overeach other and the systematic error is small but naturallyincreases with decreasing share of the analyzed ionThe trendof the systematic error is shown in Figure 3(a) by means ofsolid lines Both methods overestimate the content of boronin the sample and underestimate the content of alkali Forcompensation of the systematic error the following equationshave been obtained for the method of differentiation
120573OHminus = [138 minus 04120596minus005
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [120596minus005
BH4
minus+BO2
minus minus 0025]minus1
(21)
and for the method of simulation
120573OHminus = [139 minus 04120596minus008
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [07120596minus005
BH4
minus+BO2
minus + 028]minus1
(22)
After analysis and the determination of the components119899OHminus and 119899BH
4
minus+BO2
minus a correction procedure was carried outby multiplying the values 119899
119894
found by the correspondingcorrection coefficients 120573
119894
calculated from formulae (21) or(22) Finally the corrected amounts of the 119894th component inthe sample 119899
119894cor are
119899119894cor = 120573119894119899119894 (23)
Figure 3(b) shows the result of correction of the data given inFigure 3(a)The systematic error was totally compensated forall the variants of analysis (Table 3)
0 2 4 6 8 10Vt (mL)
minus600
minus200
200
600
1000
E(m
V)
Vlowastt
minus27000
minus18000
minus9000
0
9000
dEdVt
Figure 2 Curve of direct iodometric titration of borohydride ionsin an aqueous solution with the mixture of anions OHminus + BH
4
minus
+
BO2
minus
+ CO3
2minus (119881lowast119905
is equivalence point)
When the value of the anionic fraction 04 lt 120596119894
lt 1 allpoints lie within the ldquomeasuredweightedrdquo range 095ndash105that is the random error does not exceed 5 all points liewithin the range 088ndash112 when 005 lt 120596
119894
lt 04 that isthe random error does not exceed 12 It is only possibleto perform semiquantitative analysis of any component at itsvery small content in the mixture (120596
119894
lt 002) On correctionthe average accuracy parameter of the OHminus concentrationis 1000 for differentiation and 1001 for simulation and theaverage accuracy parameter for the (BH
4
minus
+ BO2
minus
) total is1008 for differentiation and 1004 for simulation (Table 3)
The feature of titration of alkaline-carbonate solutionsis the existence of three leaps on the titration curve(Figure 1(b))The first leap belongs to alkali while the secondand third ones are due to carbonates Correspondingly whenthe quantities of components are determined by the locationof peaks on the differential curve the quantity of CO
3
2minus isincluded twiceThe analysis of carbonate bymeans of the sec-ond peak gives a worse result than by the third one At a verysmall content of carbonate the second peak is not detectedThe average ldquomeasuredweightedrdquo value is 1215 for CO
3
2minus
ions by the second peak on the differential curve and 1115in the case of the third peak and the ldquomeasuredweightedrdquovalue is 1089 for the method of simulation The results ofcontrol determination of the alkali and carbonate contents inthe reference solutions OHminus + CO
3
2minus are shown in Figures3(c) and 3(d) for the two methods as the dependence ofthe accuracy parameter on the anionic fractions 120596
119894
In allcases the points of differentiation are more distant fromthe ldquocorrectrdquo level than those of simulation Consequentlythe method of simulation gives more correct results for theOHminus + CO
3
2minus system while the method of determinationcannot be recommended because of its high systematic errorsin carbonate analysis
The systematic error naturally increases with decreasingfractions of the analyzed ions In Figure 3(c) the trend ofsystematic errors is shown by means of solid lines for the
Journal of Fuels 7
Table 3 Average values of the ldquomeasuredweightedrdquo ratios for each ion in the mixture before and after correction of systematic errors
System Ions Method ldquoMeasuredweightedrdquo ratioBefore correction After correction
OHminus + BH4
minus + BO2
minus
OHminus Differentiation 0959 1000Simulation 0956 1001
BH4
minus + BO2
minus
Differentiation 1023 1008Simulation 1012 1004
OHminus + CO3
2minus
OHminus Simulation 0985 1003CO3
2minus Simulation 1089 0996
OHminus + BH4
minus + BO2
minus + CO3
2minus
OHminus Simulation 0874 0958BH4
minus + BO2
minus Simulation 1040 0992CO3
2minus Simulation 0934 1008
08
09
1
11
12
13
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ BH4
minus+ BO2
minus
OHminus simulationBH4
minus+ BO2
minus simulationNormOHminus differentiationBH4
minus+ BO2
minus differentiation
(a)
08
09
1
11
12
13
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ BH4
minus+ BO2
minus
OHminus simulationBH4
minus+ BO2
minus simulation + correctionNormOHminus differentiation + correctionBH4
minus+ BO2
minus differentiation + correction
(b)
05060708091
1112131415
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ CO3
2minus
OHminus simulation
NormCO3
2minus simulation
(c)
07
08
09
1
11
12
13
14
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ CO3
2minus
simulation + correctionOHminus
Normsimulation + correctionCO3
2minus
(d)
0
02
04
06
08
1
12
14
0 02 04 06 08 1
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
OHminus simulationBH4
minus+ BO2
minus simulationNormOHminus differentiation
CO32minus simulation
CO32minus differentiation
120596i
Measuredweighted
BH4minus+ BO2
minus+ CO3
2minus differentiation
(e)
Measuredweighted
02
04
06
08
1
12
14
0 02 04 06 08 1120596i
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
BH4minus+ BO2
minus simulation + correctionOHminus simulation + correction
Normsimulation + correctionCO3
2minus
(f)
Figure 3 Dependence of the ldquomeasuredweightedrdquo ratios for anions on their mole fraction 120596119894
in the mixture (a) for the OHminus + BH4
minus
+
BO2
minus system before correction of systematic errors (b) for the OHminus + BH4
minus
+ BO2
minus system after correction of systematic errors (c) for theOHminus +CO
3
2minus system before correction of systematic errors (d) for the OHminus +CO3
2minus system after correction of systematic errors (e) for theOHminus + BH
4
minus
+ BO2
minus
+CO3
2minus system before correction of systematic errors (f) for the OHminus + BH4
minus
+ BO2
minus
+CO3
2minus system after correctionof systematic errors The solid lines show the average trend of errors The dotted lines show the error interval for the method of simulation
8 Journal of Fuels
method of simulation The following equations have beensuggested for compensation of this trend
120573OHminus = [29 minus 19120596minus0055
OHminus ]minus1
120573CO3
2minus = [75120596minus001
CO3
2minus minus 65]minus1
(24)
After analysis and the determination of the 119899OHminus and 119899CO3
2minus
values a correction procedure is carried out by formula(24) Figure 3(d) shows the result of such correction Thesystematic error is completely compensated (Table 3) Allpoints lie within the ldquomeasuredweightedrdquo range 095ndash105for the anionic fractions within 04 lt 120596
119894
lt 1 that is therandom error does not exceed 5 and the random scatteringdoes not exceed 12 when 015 lt 120596
119894
lt 04 If the fractionof carbonate is less than 015 the reliability of its analysisdecreases because of the high random dispersion thereforeit is required to increase the number of replicate samplesThedirect titrimetric analysis of carbonate becomes impossiblewhen 120596CO
3
2minus lt 0015A feature of titration of alkaline-borohydride-borate-
carbonate solutions is the existence of three weak leaps onthe titration curve (Figure 1(d)) The first leap belongs toalkali while the second belongs to the ldquoBH
4
minus
+ BO2
minus
+
CO3
2minusrdquo total and the third one belongs to carbonate ionsRespectively at the quantification of components by meansof the position of peaks on the differential curve the totalcontent of boron 119899BH
4
minus+BO2
minus can be only calculated after thedetermination and extraction of the carbonate quantity
The results of our control determination of the anioncontents in the OHminus + BH
4
minus
+ BO2
minus
+ CO3
2minus mixturesby both methods are shown in Figure 3(e) The methodof differentiation gives an unsatisfactory result for car-bonate underestimating its content significantly the meanldquomeasuredweightedrdquo value being 0615 The carbonate peakdisappears when 120596CO
3
2minus lt 015 which leads to incorrectdetermination of the BH
4
minus
+ BO2
minus total Therefore for theOHminus+ BH
4
minus
+ BO2
minus
+ CO3
2minus system (the highly carbonatedand discharged fuel) the method of differentiation cannotbe recommended because of its large systematic errors incarbonate analysis and the method of simulation is onlysuggested for use The mean ldquomeasuredweightedrdquo values areshown in Table 3 The determination accuracy is 0874 forOHminus ions 1040 for the BH
4
minus
+ BO2
minus total and 0934 forCO3
2minus ions After correction these parameters become 09580992 and 1008 respectively The correcting coefficients are
120573OHminus = [198 minus 120596minus005
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [120596minus0085
BH4
minus+BO2
minus minus 003]minus1
120573CO3
2minus = [195 minus 120596minus001
CO3
2minus]minus1
(25)
The systematic error is thus compensated however therandom scattering of the points is higher than with moresimple options The random dispersion for alkali and borondoes not exceed 15 (all points arewithin 085ndash115) howeverit is only fair for carbonatewhen120596CO
3
2minus gt 01 If the carbonate
content is less than 01 its semiquantitative analysis is onlypossible But very small amounts of carbonate will not affectthe functioning of DBFC and only higher concentrations ofcarbonate exceeding the solubility limit can be deposited inthe electrode to hinder the functioning of DBFC
4 Conclusions
Theanalytic technique presented in our paper includes takinga small fuel sample from DBFC and performing two types oftitrations (acid-base and iodometric ones) which supplementeach otherThenecessity of exactly two techniques of titrationis due to the fact that iodometric titration determines theBH4
minus quantity in the sample only while the quantities ofother fuel components are provided by acid-base titration(OHminus BO
2
minus CO3
2minus)Therefore the joint application of thesetitration techniques allows one to most fully quantify thecurrent state of fuel in the process of DBFC functioningThe determination correctness of the technique has beenshown on artificial mixtures with a wide variation of theircomposition The average error depends on the number ofcomponents and their ratio in the mixture The investigationresults show that in the most complex case of highly carbon-ated and discharged fuel the maximal error of determinationdoes not exceed 15
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgment
The authors would like to gratefully acknowledge the RussianFoundation for Basic Research for financial support (Projectno 12-03-31802)
References
[1] J B Lakeman A Rose K D Pointon et al ldquoThe directborohydride fuel cell for UUV propulsion powerrdquo Journal ofPower Sources vol 162 no 2 pp 765ndash772 2006
[2] C P de Leon F C Walsh D Pletcher D J Browning and JB Lakeman ldquoDirect borohydride fuel cellsrdquo Journal of PowerSources vol 155 no 2 pp 172ndash181 2006
[3] R Aiello J H Sharp and M A Matthews ldquoProduction ofhydrogen from chemical hydrides via hydrolysis with steamrdquoInternational Journal of Hydrogen Energy vol 24 no 12 pp1123ndash1130 1999
[4] S C Amendola S L Sharp-Goldman M S Janjua et al ldquoSafeportable hydrogen gas generator using aqueous borohydridesolution and Ru catalystrdquo International Journal of HydrogenEnergy vol 25 no 10 pp 969ndash975 2000
[5] H I Schlesinger H C Brown A E Finholt J R GilbreathH R Hoekstra and E K Hyde ldquoSodium borohydride itshydrolysis and its use as a reducing agent and in the generationof hydrogenrdquo Journal of the American Chemical Society vol 75no 1 pp 215ndash219 1953
Journal of Fuels 9
[6] S C Amendola P Onnerud M T Kelly P J Petillo S LSharp-Goldman and M Binder ldquoNovel high power densityborohydride-air cellrdquo Journal of Power Sources vol 84 no 1 pp130ndash133 1999
[7] B H Liu and Z P Li ldquoCurrent status and progress of directborohydride fuel cell technology developmentrdquo Journal ofPower Sources vol 187 no 2 pp 291ndash297 2009
[8] B H Liu and Z P Li ldquoA review hydrogen generation fromborohydride hydrolysis reactionrdquo Journal of Power Sources vol187 no 2 pp 527ndash534 2009
[9] B Weng Z Wu Z Li H Yang and H Leng ldquoHydrogengeneration from noncatalytic hydrolysis of LiBH4NH3BH3mixture for fuel cell applicationsrdquo International Journal ofHydrogen Energy vol 36 no 17 pp 10870ndash10876 2011
[10] A E Sanli I Kayacan B Z Uysal and M L Aksu ldquoRecoveryof borohydride from metaborate solution using a silver catalystfor application of direct rechargable borohydrideperoxide fuelcellsrdquo Journal of Power Sources vol 195 no 9 pp 2604ndash26072010
[11] R Jamard J Salomon A Martinent-Beaumont and CCoutanceau ldquoLife time test in direct borohydride fuel cellsystemrdquo Journal of Power Sources vol 193 no 2 pp 779ndash7872009
[12] J-H Wee ldquoA comparison of sodium borohydride as a fuel forproton exchange membrane fuel cells and for direct borohy-dride fuel cellsrdquo Journal of Power Sources vol 155 no 2 pp329ndash339 2006
[13] A V Churikov K V Zapsis V V Khramkov M A ChurikovM P Smotrov and I A Kazarinov ldquoPhase diagrams of theternary systems NaBH
4
+ NaOH + H2
O KBH4
+ KOH + H2
ONaBO
2
+ NaOH + H2
O and KBO2
+ KOH + H2
O at minus10∘CrdquoJournal of Chemical and Engineering Data vol 56 no 1 pp 9ndash13 2011
[14] A V Churikov K V Zapsis V V Khramkov M A Churikovand I M Gamayunova ldquoTemperature-induced transformationof the phase diagrams of ternary systems NaBO
2
+ NaOH+ H2
O and KBO2
+ KOH + H2
Ordquo Journal of Chemical andEngineering Data vol 56 no 3 pp 383ndash389 2011
[15] A V Churikov K V Zapsis A V Ivanishchev and V OSychova ldquoTemperature-induced transformation of the phasediagrams of ternary systems NaBH
4
+ NaOH +H2
O and KBH4
+ KOH + H2
Ordquo Journal of Chemical and Engineering Data vol56 no 5 pp 2543ndash2552 2011
[16] G Rostamikiaa and M J Janik ldquoDirect borohydride oxidationmechanism determination and design of alloy catalysts guidedby density functional theoryrdquo Energy amp Environmental Sciencevol 3 pp 1262ndash1274 2010
[17] B Sljuki J Miliki D M F Santosa and C A C SequeiraldquoCarbon-supported Pt
075
M025
(M = Ni or Co) electrocatalystsfor borohydride oxidationrdquo Electrochim Acta vol 107 pp 577ndash583 2013
[18] B H Liu J Q Yang and Z P Li ldquoConcentration ratio of[OHminus][BH
4
minus] a controlling factor for the fuel efficiency ofborohydride electro-oxidationrdquo International Journal of Hydro-gen Energy vol 34 no 23 pp 9436ndash9443 2009
[19] A V Churikov A V Ivanishchev I M Gamayunova andA V Ushakov ldquoDensity calculations for (Na K)BH
4
+ (NaK)BO
2
+ (Na K)OH + H2
O solutions used in hydrogen powerengineeringrdquo Journal of Chemical and Engineering Data vol 56no 11 pp 3984ndash3993 2011
[20] A V Churikov V O Romanova M A Churikov and I MGamayunova ldquoThemodel of fuel transformation at discharge of
direct borohydride fuel cellrdquo International Review of ChemicalEngineering vol 4 pp 263ndash268 2012
[21] A V Churikov I M Gamayunova K V Zapsis M AChurikov and A V Ivanishchev ldquoInfluence of temperature andalkalinity on the hydrolysis rate of borohydride ions in aqueoussolutionrdquo International Journal of Hydrogen Energy vol 37 no1 pp 335ndash344 2012
[22] Z P Li B H Liu K Arai and S Suda ldquoA fuel cell developmentfor using borohydrides as the fuelrdquo Journal of the Electrochemi-cal Society vol 150 no 7 pp A868ndashA872 2003
[23] Y Wang P Hea and H Zhou ldquoA novel direct borohydridefuel cell using an acid-alkaline hybrid electrolyterdquo Energy ampEnvironmental Science vol 3 no 10 pp 1515ndash1518 2010
[24] J Ma N A Choudhury and Y Sahai ldquoA comprehensive reviewof direct borohydride fuel cellsrdquo Renewable and SustainableEnergy Reviews vol 14 no 1 pp 183ndash199 2010
[25] R Bruhlmann and L Piatti ldquoAn improved method for thetitrimetric determination of boron in ironrdquo Chimia vol 11 p203 1957
[26] A Keshan and C Bimba ldquoCobalt-potassium and ammonium-cobalt dodecaboraterdquo Izvestiya Akademii Nauk Latvijskoj SSRp 115 1954
[27] J Czakow T Steciak and O Szczebinska ldquoThe spectral deter-mination of trace amounts of impurities in the solutions withthe metal electrodes in the spark moderdquo Analytical Chemistryvol 3 p 745 1958
[28] R Rosotti ldquoA fast method for the determination of traceamounts of boron in the steelrdquo Analytical Chemistry vol 44 p208 1962
[29] J Varka and A Sklaf ldquoApplication of potentiometric titrationIV Determination of B
2
O3
in glass enamels and boron-containing raw materialsrdquo Keramik vol 7 p 12 1957
[30] D E Williams and J Vilamis ldquoStability of the curcumincomplex in boron determinationrdquoAnalytical Chemistry vol 33pp 1098ndash1100 1961
[31] S Kertes and M Lederer ldquoPaper chromatography of inorganicions Rf values in mixtures of butanol and Hbrrdquo AnalyticaChimica Acta vol 15 no C pp 543ndash547 1956
[32] A A Nemodruk and Z K Karalova The Analytical Chemistryof Boron Nauka 1964
[33] C A Parker ldquoRaman spectra in spectrofluorimetryrdquo The Ana-lyst vol 84 no 1000 pp 446ndash453 1959
[34] C A Parker and W J Barnes ldquoFluorimetric determination ofboron application to silicon sea water and steelrdquo The Analystvol 85 no 1016 pp 828ndash838 1960
[35] M V Akhmanova Methods of Determination and Analysis ofRear Elements Izdat Akademija Nauk SSSR 1961
[36] E H Jensen A Study on Sodium Borohydride Nyt NordiskForlag Amold Busck Copenhagen Denmark 1954
[37] I Fatt and M Tashima Alkali Metal Dispersions D VanNostrand Co Inc Princeton NJ USA 1961
[38] DA Lyttle EH Jensen andWA Struck ldquoA simple volumetricassay for sodium borohydriderdquo Analytical Chemistry vol 24no 11 pp 1843ndash1844 1952
[39] P K Norkus ldquoIodometric determination of borohydriderdquoRussian Journal of Analytical Chemistry vol 23 pp 908ndash9111968
[40] N N Malrsquoceva and V S Khain Sodium Borohydride Propertiesand Application Nauka 1985
10 Journal of Fuels
[41] C Harzdorf and O Steinhauser ldquoZur photometrisehen Titra-tion von Fluorid mit Thoriumnitratrdquo Freseniusrsquo Zeitschrift furAnalytische Chemie vol 210 no 2 pp 106ndash112 1965
[42] W D Davis L S Mason and G Stegeman ldquoThe heats offormation of sodium borohydride lithium borohydride andlithium aluminum hydriderdquo Journal of the American ChemicalSociety vol 71 no 8 pp 2775ndash2781 1949
[43] S W Chaikin ldquoDirect volumetric assay of sodium borohydrideand potassium borohydriderdquo Analytical Chemistry vol 25 no5 pp 831ndash832 1953
[44] U Ulku and G Somer ldquoDetermination of trace borohydride inbasic solutions using differential pulse polarographyrdquo TurkishJournal of Chemistry vol 33 pp 657ndash665 2009
[45] H Celikkan H Aydin and M L Aksu ldquoThe electroanalyticaldetermination of sodium borohydride using a gold electroderdquoTurkish Journal of Chemistry vol 29 pp 519ndash524 2005
[46] M V Mirkin and A J Bard ldquoVoltammetric method forthe determination of borohydride concentration in alkalineaqueous solutionsrdquoAnalytical Chemistry vol 63 no 5 pp 532ndash533 1991
[47] D M F Santos and C A C Sequeira ldquoPotentiometric moni-toring of sodium borohydride in aqueous solutionsrdquo Ciencia sTecnologia dos Materials vol 20 no 3-4 pp 31ndash34 2008
[48] D M F Santos and C A C Sequeira ldquoSodium borohydridedetermination by measurement of open circuit potentialsrdquoJournal of Electroanalytical Chemistry vol 627 pp 1ndash8 2009
[49] H C Brown and A C Boyd Jr ldquoArgentimetric procedure forborohydride determinationrdquo Analytical Chemistry vol 27 no1 pp 156ndash158 1955
[50] V B Breicis A O Berzina and L K Lepin ldquoPotentiomet-ric titration of water solutions of sodium borohydride byhydrochloric acidrdquo Scientific Short Letter of Riga PolytechnicInstitute vol 15 pp 179ndash188 19651966
[51] U U Lurie Handbook on Analytical Chemistry Khimiya 1979[52] R A Lidin L L Andreeva and V A Molochko Hand-
book of Inorganic Chemistry Constants of Inorganic SubstancesKhimiya 1987
[53] R A Robinson and R H Stokes Electrolyte Solutions the Mea-surement and Interpretation of Conductance Chemical Potentialand Diffusion in Solutions of Simple Electrolytes ButterworthsLondon UK 1959
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
CombustionJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
StructuresJournal of
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear InstallationsScience and Technology of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Solar EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Wind EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear EnergyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Journal of Fuels 7
Table 3 Average values of the ldquomeasuredweightedrdquo ratios for each ion in the mixture before and after correction of systematic errors
System Ions Method ldquoMeasuredweightedrdquo ratioBefore correction After correction
OHminus + BH4
minus + BO2
minus
OHminus Differentiation 0959 1000Simulation 0956 1001
BH4
minus + BO2
minus
Differentiation 1023 1008Simulation 1012 1004
OHminus + CO3
2minus
OHminus Simulation 0985 1003CO3
2minus Simulation 1089 0996
OHminus + BH4
minus + BO2
minus + CO3
2minus
OHminus Simulation 0874 0958BH4
minus + BO2
minus Simulation 1040 0992CO3
2minus Simulation 0934 1008
08
09
1
11
12
13
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ BH4
minus+ BO2
minus
OHminus simulationBH4
minus+ BO2
minus simulationNormOHminus differentiationBH4
minus+ BO2
minus differentiation
(a)
08
09
1
11
12
13
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ BH4
minus+ BO2
minus
OHminus simulationBH4
minus+ BO2
minus simulation + correctionNormOHminus differentiation + correctionBH4
minus+ BO2
minus differentiation + correction
(b)
05060708091
1112131415
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ CO3
2minus
OHminus simulation
NormCO3
2minus simulation
(c)
07
08
09
1
11
12
13
14
0 02 04 06 08 1
Measuredweighted
120596i
OHminus+ CO3
2minus
simulation + correctionOHminus
Normsimulation + correctionCO3
2minus
(d)
0
02
04
06
08
1
12
14
0 02 04 06 08 1
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
OHminus simulationBH4
minus+ BO2
minus simulationNormOHminus differentiation
CO32minus simulation
CO32minus differentiation
120596i
Measuredweighted
BH4minus+ BO2
minus+ CO3
2minus differentiation
(e)
Measuredweighted
02
04
06
08
1
12
14
0 02 04 06 08 1120596i
OHminus+ BH4
minus+ BO2
minus+ CO3
2minus
BH4minus+ BO2
minus simulation + correctionOHminus simulation + correction
Normsimulation + correctionCO3
2minus
(f)
Figure 3 Dependence of the ldquomeasuredweightedrdquo ratios for anions on their mole fraction 120596119894
in the mixture (a) for the OHminus + BH4
minus
+
BO2
minus system before correction of systematic errors (b) for the OHminus + BH4
minus
+ BO2
minus system after correction of systematic errors (c) for theOHminus +CO
3
2minus system before correction of systematic errors (d) for the OHminus +CO3
2minus system after correction of systematic errors (e) for theOHminus + BH
4
minus
+ BO2
minus
+CO3
2minus system before correction of systematic errors (f) for the OHminus + BH4
minus
+ BO2
minus
+CO3
2minus system after correctionof systematic errors The solid lines show the average trend of errors The dotted lines show the error interval for the method of simulation
8 Journal of Fuels
method of simulation The following equations have beensuggested for compensation of this trend
120573OHminus = [29 minus 19120596minus0055
OHminus ]minus1
120573CO3
2minus = [75120596minus001
CO3
2minus minus 65]minus1
(24)
After analysis and the determination of the 119899OHminus and 119899CO3
2minus
values a correction procedure is carried out by formula(24) Figure 3(d) shows the result of such correction Thesystematic error is completely compensated (Table 3) Allpoints lie within the ldquomeasuredweightedrdquo range 095ndash105for the anionic fractions within 04 lt 120596
119894
lt 1 that is therandom error does not exceed 5 and the random scatteringdoes not exceed 12 when 015 lt 120596
119894
lt 04 If the fractionof carbonate is less than 015 the reliability of its analysisdecreases because of the high random dispersion thereforeit is required to increase the number of replicate samplesThedirect titrimetric analysis of carbonate becomes impossiblewhen 120596CO
3
2minus lt 0015A feature of titration of alkaline-borohydride-borate-
carbonate solutions is the existence of three weak leaps onthe titration curve (Figure 1(d)) The first leap belongs toalkali while the second belongs to the ldquoBH
4
minus
+ BO2
minus
+
CO3
2minusrdquo total and the third one belongs to carbonate ionsRespectively at the quantification of components by meansof the position of peaks on the differential curve the totalcontent of boron 119899BH
4
minus+BO2
minus can be only calculated after thedetermination and extraction of the carbonate quantity
The results of our control determination of the anioncontents in the OHminus + BH
4
minus
+ BO2
minus
+ CO3
2minus mixturesby both methods are shown in Figure 3(e) The methodof differentiation gives an unsatisfactory result for car-bonate underestimating its content significantly the meanldquomeasuredweightedrdquo value being 0615 The carbonate peakdisappears when 120596CO
3
2minus lt 015 which leads to incorrectdetermination of the BH
4
minus
+ BO2
minus total Therefore for theOHminus+ BH
4
minus
+ BO2
minus
+ CO3
2minus system (the highly carbonatedand discharged fuel) the method of differentiation cannotbe recommended because of its large systematic errors incarbonate analysis and the method of simulation is onlysuggested for use The mean ldquomeasuredweightedrdquo values areshown in Table 3 The determination accuracy is 0874 forOHminus ions 1040 for the BH
4
minus
+ BO2
minus total and 0934 forCO3
2minus ions After correction these parameters become 09580992 and 1008 respectively The correcting coefficients are
120573OHminus = [198 minus 120596minus005
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [120596minus0085
BH4
minus+BO2
minus minus 003]minus1
120573CO3
2minus = [195 minus 120596minus001
CO3
2minus]minus1
(25)
The systematic error is thus compensated however therandom scattering of the points is higher than with moresimple options The random dispersion for alkali and borondoes not exceed 15 (all points arewithin 085ndash115) howeverit is only fair for carbonatewhen120596CO
3
2minus gt 01 If the carbonate
content is less than 01 its semiquantitative analysis is onlypossible But very small amounts of carbonate will not affectthe functioning of DBFC and only higher concentrations ofcarbonate exceeding the solubility limit can be deposited inthe electrode to hinder the functioning of DBFC
4 Conclusions
Theanalytic technique presented in our paper includes takinga small fuel sample from DBFC and performing two types oftitrations (acid-base and iodometric ones) which supplementeach otherThenecessity of exactly two techniques of titrationis due to the fact that iodometric titration determines theBH4
minus quantity in the sample only while the quantities ofother fuel components are provided by acid-base titration(OHminus BO
2
minus CO3
2minus)Therefore the joint application of thesetitration techniques allows one to most fully quantify thecurrent state of fuel in the process of DBFC functioningThe determination correctness of the technique has beenshown on artificial mixtures with a wide variation of theircomposition The average error depends on the number ofcomponents and their ratio in the mixture The investigationresults show that in the most complex case of highly carbon-ated and discharged fuel the maximal error of determinationdoes not exceed 15
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgment
The authors would like to gratefully acknowledge the RussianFoundation for Basic Research for financial support (Projectno 12-03-31802)
References
[1] J B Lakeman A Rose K D Pointon et al ldquoThe directborohydride fuel cell for UUV propulsion powerrdquo Journal ofPower Sources vol 162 no 2 pp 765ndash772 2006
[2] C P de Leon F C Walsh D Pletcher D J Browning and JB Lakeman ldquoDirect borohydride fuel cellsrdquo Journal of PowerSources vol 155 no 2 pp 172ndash181 2006
[3] R Aiello J H Sharp and M A Matthews ldquoProduction ofhydrogen from chemical hydrides via hydrolysis with steamrdquoInternational Journal of Hydrogen Energy vol 24 no 12 pp1123ndash1130 1999
[4] S C Amendola S L Sharp-Goldman M S Janjua et al ldquoSafeportable hydrogen gas generator using aqueous borohydridesolution and Ru catalystrdquo International Journal of HydrogenEnergy vol 25 no 10 pp 969ndash975 2000
[5] H I Schlesinger H C Brown A E Finholt J R GilbreathH R Hoekstra and E K Hyde ldquoSodium borohydride itshydrolysis and its use as a reducing agent and in the generationof hydrogenrdquo Journal of the American Chemical Society vol 75no 1 pp 215ndash219 1953
Journal of Fuels 9
[6] S C Amendola P Onnerud M T Kelly P J Petillo S LSharp-Goldman and M Binder ldquoNovel high power densityborohydride-air cellrdquo Journal of Power Sources vol 84 no 1 pp130ndash133 1999
[7] B H Liu and Z P Li ldquoCurrent status and progress of directborohydride fuel cell technology developmentrdquo Journal ofPower Sources vol 187 no 2 pp 291ndash297 2009
[8] B H Liu and Z P Li ldquoA review hydrogen generation fromborohydride hydrolysis reactionrdquo Journal of Power Sources vol187 no 2 pp 527ndash534 2009
[9] B Weng Z Wu Z Li H Yang and H Leng ldquoHydrogengeneration from noncatalytic hydrolysis of LiBH4NH3BH3mixture for fuel cell applicationsrdquo International Journal ofHydrogen Energy vol 36 no 17 pp 10870ndash10876 2011
[10] A E Sanli I Kayacan B Z Uysal and M L Aksu ldquoRecoveryof borohydride from metaborate solution using a silver catalystfor application of direct rechargable borohydrideperoxide fuelcellsrdquo Journal of Power Sources vol 195 no 9 pp 2604ndash26072010
[11] R Jamard J Salomon A Martinent-Beaumont and CCoutanceau ldquoLife time test in direct borohydride fuel cellsystemrdquo Journal of Power Sources vol 193 no 2 pp 779ndash7872009
[12] J-H Wee ldquoA comparison of sodium borohydride as a fuel forproton exchange membrane fuel cells and for direct borohy-dride fuel cellsrdquo Journal of Power Sources vol 155 no 2 pp329ndash339 2006
[13] A V Churikov K V Zapsis V V Khramkov M A ChurikovM P Smotrov and I A Kazarinov ldquoPhase diagrams of theternary systems NaBH
4
+ NaOH + H2
O KBH4
+ KOH + H2
ONaBO
2
+ NaOH + H2
O and KBO2
+ KOH + H2
O at minus10∘CrdquoJournal of Chemical and Engineering Data vol 56 no 1 pp 9ndash13 2011
[14] A V Churikov K V Zapsis V V Khramkov M A Churikovand I M Gamayunova ldquoTemperature-induced transformationof the phase diagrams of ternary systems NaBO
2
+ NaOH+ H2
O and KBO2
+ KOH + H2
Ordquo Journal of Chemical andEngineering Data vol 56 no 3 pp 383ndash389 2011
[15] A V Churikov K V Zapsis A V Ivanishchev and V OSychova ldquoTemperature-induced transformation of the phasediagrams of ternary systems NaBH
4
+ NaOH +H2
O and KBH4
+ KOH + H2
Ordquo Journal of Chemical and Engineering Data vol56 no 5 pp 2543ndash2552 2011
[16] G Rostamikiaa and M J Janik ldquoDirect borohydride oxidationmechanism determination and design of alloy catalysts guidedby density functional theoryrdquo Energy amp Environmental Sciencevol 3 pp 1262ndash1274 2010
[17] B Sljuki J Miliki D M F Santosa and C A C SequeiraldquoCarbon-supported Pt
075
M025
(M = Ni or Co) electrocatalystsfor borohydride oxidationrdquo Electrochim Acta vol 107 pp 577ndash583 2013
[18] B H Liu J Q Yang and Z P Li ldquoConcentration ratio of[OHminus][BH
4
minus] a controlling factor for the fuel efficiency ofborohydride electro-oxidationrdquo International Journal of Hydro-gen Energy vol 34 no 23 pp 9436ndash9443 2009
[19] A V Churikov A V Ivanishchev I M Gamayunova andA V Ushakov ldquoDensity calculations for (Na K)BH
4
+ (NaK)BO
2
+ (Na K)OH + H2
O solutions used in hydrogen powerengineeringrdquo Journal of Chemical and Engineering Data vol 56no 11 pp 3984ndash3993 2011
[20] A V Churikov V O Romanova M A Churikov and I MGamayunova ldquoThemodel of fuel transformation at discharge of
direct borohydride fuel cellrdquo International Review of ChemicalEngineering vol 4 pp 263ndash268 2012
[21] A V Churikov I M Gamayunova K V Zapsis M AChurikov and A V Ivanishchev ldquoInfluence of temperature andalkalinity on the hydrolysis rate of borohydride ions in aqueoussolutionrdquo International Journal of Hydrogen Energy vol 37 no1 pp 335ndash344 2012
[22] Z P Li B H Liu K Arai and S Suda ldquoA fuel cell developmentfor using borohydrides as the fuelrdquo Journal of the Electrochemi-cal Society vol 150 no 7 pp A868ndashA872 2003
[23] Y Wang P Hea and H Zhou ldquoA novel direct borohydridefuel cell using an acid-alkaline hybrid electrolyterdquo Energy ampEnvironmental Science vol 3 no 10 pp 1515ndash1518 2010
[24] J Ma N A Choudhury and Y Sahai ldquoA comprehensive reviewof direct borohydride fuel cellsrdquo Renewable and SustainableEnergy Reviews vol 14 no 1 pp 183ndash199 2010
[25] R Bruhlmann and L Piatti ldquoAn improved method for thetitrimetric determination of boron in ironrdquo Chimia vol 11 p203 1957
[26] A Keshan and C Bimba ldquoCobalt-potassium and ammonium-cobalt dodecaboraterdquo Izvestiya Akademii Nauk Latvijskoj SSRp 115 1954
[27] J Czakow T Steciak and O Szczebinska ldquoThe spectral deter-mination of trace amounts of impurities in the solutions withthe metal electrodes in the spark moderdquo Analytical Chemistryvol 3 p 745 1958
[28] R Rosotti ldquoA fast method for the determination of traceamounts of boron in the steelrdquo Analytical Chemistry vol 44 p208 1962
[29] J Varka and A Sklaf ldquoApplication of potentiometric titrationIV Determination of B
2
O3
in glass enamels and boron-containing raw materialsrdquo Keramik vol 7 p 12 1957
[30] D E Williams and J Vilamis ldquoStability of the curcumincomplex in boron determinationrdquoAnalytical Chemistry vol 33pp 1098ndash1100 1961
[31] S Kertes and M Lederer ldquoPaper chromatography of inorganicions Rf values in mixtures of butanol and Hbrrdquo AnalyticaChimica Acta vol 15 no C pp 543ndash547 1956
[32] A A Nemodruk and Z K Karalova The Analytical Chemistryof Boron Nauka 1964
[33] C A Parker ldquoRaman spectra in spectrofluorimetryrdquo The Ana-lyst vol 84 no 1000 pp 446ndash453 1959
[34] C A Parker and W J Barnes ldquoFluorimetric determination ofboron application to silicon sea water and steelrdquo The Analystvol 85 no 1016 pp 828ndash838 1960
[35] M V Akhmanova Methods of Determination and Analysis ofRear Elements Izdat Akademija Nauk SSSR 1961
[36] E H Jensen A Study on Sodium Borohydride Nyt NordiskForlag Amold Busck Copenhagen Denmark 1954
[37] I Fatt and M Tashima Alkali Metal Dispersions D VanNostrand Co Inc Princeton NJ USA 1961
[38] DA Lyttle EH Jensen andWA Struck ldquoA simple volumetricassay for sodium borohydriderdquo Analytical Chemistry vol 24no 11 pp 1843ndash1844 1952
[39] P K Norkus ldquoIodometric determination of borohydriderdquoRussian Journal of Analytical Chemistry vol 23 pp 908ndash9111968
[40] N N Malrsquoceva and V S Khain Sodium Borohydride Propertiesand Application Nauka 1985
10 Journal of Fuels
[41] C Harzdorf and O Steinhauser ldquoZur photometrisehen Titra-tion von Fluorid mit Thoriumnitratrdquo Freseniusrsquo Zeitschrift furAnalytische Chemie vol 210 no 2 pp 106ndash112 1965
[42] W D Davis L S Mason and G Stegeman ldquoThe heats offormation of sodium borohydride lithium borohydride andlithium aluminum hydriderdquo Journal of the American ChemicalSociety vol 71 no 8 pp 2775ndash2781 1949
[43] S W Chaikin ldquoDirect volumetric assay of sodium borohydrideand potassium borohydriderdquo Analytical Chemistry vol 25 no5 pp 831ndash832 1953
[44] U Ulku and G Somer ldquoDetermination of trace borohydride inbasic solutions using differential pulse polarographyrdquo TurkishJournal of Chemistry vol 33 pp 657ndash665 2009
[45] H Celikkan H Aydin and M L Aksu ldquoThe electroanalyticaldetermination of sodium borohydride using a gold electroderdquoTurkish Journal of Chemistry vol 29 pp 519ndash524 2005
[46] M V Mirkin and A J Bard ldquoVoltammetric method forthe determination of borohydride concentration in alkalineaqueous solutionsrdquoAnalytical Chemistry vol 63 no 5 pp 532ndash533 1991
[47] D M F Santos and C A C Sequeira ldquoPotentiometric moni-toring of sodium borohydride in aqueous solutionsrdquo Ciencia sTecnologia dos Materials vol 20 no 3-4 pp 31ndash34 2008
[48] D M F Santos and C A C Sequeira ldquoSodium borohydridedetermination by measurement of open circuit potentialsrdquoJournal of Electroanalytical Chemistry vol 627 pp 1ndash8 2009
[49] H C Brown and A C Boyd Jr ldquoArgentimetric procedure forborohydride determinationrdquo Analytical Chemistry vol 27 no1 pp 156ndash158 1955
[50] V B Breicis A O Berzina and L K Lepin ldquoPotentiomet-ric titration of water solutions of sodium borohydride byhydrochloric acidrdquo Scientific Short Letter of Riga PolytechnicInstitute vol 15 pp 179ndash188 19651966
[51] U U Lurie Handbook on Analytical Chemistry Khimiya 1979[52] R A Lidin L L Andreeva and V A Molochko Hand-
book of Inorganic Chemistry Constants of Inorganic SubstancesKhimiya 1987
[53] R A Robinson and R H Stokes Electrolyte Solutions the Mea-surement and Interpretation of Conductance Chemical Potentialand Diffusion in Solutions of Simple Electrolytes ButterworthsLondon UK 1959
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
CombustionJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
StructuresJournal of
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear InstallationsScience and Technology of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Solar EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Wind EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear EnergyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
8 Journal of Fuels
method of simulation The following equations have beensuggested for compensation of this trend
120573OHminus = [29 minus 19120596minus0055
OHminus ]minus1
120573CO3
2minus = [75120596minus001
CO3
2minus minus 65]minus1
(24)
After analysis and the determination of the 119899OHminus and 119899CO3
2minus
values a correction procedure is carried out by formula(24) Figure 3(d) shows the result of such correction Thesystematic error is completely compensated (Table 3) Allpoints lie within the ldquomeasuredweightedrdquo range 095ndash105for the anionic fractions within 04 lt 120596
119894
lt 1 that is therandom error does not exceed 5 and the random scatteringdoes not exceed 12 when 015 lt 120596
119894
lt 04 If the fractionof carbonate is less than 015 the reliability of its analysisdecreases because of the high random dispersion thereforeit is required to increase the number of replicate samplesThedirect titrimetric analysis of carbonate becomes impossiblewhen 120596CO
3
2minus lt 0015A feature of titration of alkaline-borohydride-borate-
carbonate solutions is the existence of three weak leaps onthe titration curve (Figure 1(d)) The first leap belongs toalkali while the second belongs to the ldquoBH
4
minus
+ BO2
minus
+
CO3
2minusrdquo total and the third one belongs to carbonate ionsRespectively at the quantification of components by meansof the position of peaks on the differential curve the totalcontent of boron 119899BH
4
minus+BO2
minus can be only calculated after thedetermination and extraction of the carbonate quantity
The results of our control determination of the anioncontents in the OHminus + BH
4
minus
+ BO2
minus
+ CO3
2minus mixturesby both methods are shown in Figure 3(e) The methodof differentiation gives an unsatisfactory result for car-bonate underestimating its content significantly the meanldquomeasuredweightedrdquo value being 0615 The carbonate peakdisappears when 120596CO
3
2minus lt 015 which leads to incorrectdetermination of the BH
4
minus
+ BO2
minus total Therefore for theOHminus+ BH
4
minus
+ BO2
minus
+ CO3
2minus system (the highly carbonatedand discharged fuel) the method of differentiation cannotbe recommended because of its large systematic errors incarbonate analysis and the method of simulation is onlysuggested for use The mean ldquomeasuredweightedrdquo values areshown in Table 3 The determination accuracy is 0874 forOHminus ions 1040 for the BH
4
minus
+ BO2
minus total and 0934 forCO3
2minus ions After correction these parameters become 09580992 and 1008 respectively The correcting coefficients are
120573OHminus = [198 minus 120596minus005
OHminus ]minus1
120573(BH4
minus+BO2
minus)
= [120596minus0085
BH4
minus+BO2
minus minus 003]minus1
120573CO3
2minus = [195 minus 120596minus001
CO3
2minus]minus1
(25)
The systematic error is thus compensated however therandom scattering of the points is higher than with moresimple options The random dispersion for alkali and borondoes not exceed 15 (all points arewithin 085ndash115) howeverit is only fair for carbonatewhen120596CO
3
2minus gt 01 If the carbonate
content is less than 01 its semiquantitative analysis is onlypossible But very small amounts of carbonate will not affectthe functioning of DBFC and only higher concentrations ofcarbonate exceeding the solubility limit can be deposited inthe electrode to hinder the functioning of DBFC
4 Conclusions
Theanalytic technique presented in our paper includes takinga small fuel sample from DBFC and performing two types oftitrations (acid-base and iodometric ones) which supplementeach otherThenecessity of exactly two techniques of titrationis due to the fact that iodometric titration determines theBH4
minus quantity in the sample only while the quantities ofother fuel components are provided by acid-base titration(OHminus BO
2
minus CO3
2minus)Therefore the joint application of thesetitration techniques allows one to most fully quantify thecurrent state of fuel in the process of DBFC functioningThe determination correctness of the technique has beenshown on artificial mixtures with a wide variation of theircomposition The average error depends on the number ofcomponents and their ratio in the mixture The investigationresults show that in the most complex case of highly carbon-ated and discharged fuel the maximal error of determinationdoes not exceed 15
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgment
The authors would like to gratefully acknowledge the RussianFoundation for Basic Research for financial support (Projectno 12-03-31802)
References
[1] J B Lakeman A Rose K D Pointon et al ldquoThe directborohydride fuel cell for UUV propulsion powerrdquo Journal ofPower Sources vol 162 no 2 pp 765ndash772 2006
[2] C P de Leon F C Walsh D Pletcher D J Browning and JB Lakeman ldquoDirect borohydride fuel cellsrdquo Journal of PowerSources vol 155 no 2 pp 172ndash181 2006
[3] R Aiello J H Sharp and M A Matthews ldquoProduction ofhydrogen from chemical hydrides via hydrolysis with steamrdquoInternational Journal of Hydrogen Energy vol 24 no 12 pp1123ndash1130 1999
[4] S C Amendola S L Sharp-Goldman M S Janjua et al ldquoSafeportable hydrogen gas generator using aqueous borohydridesolution and Ru catalystrdquo International Journal of HydrogenEnergy vol 25 no 10 pp 969ndash975 2000
[5] H I Schlesinger H C Brown A E Finholt J R GilbreathH R Hoekstra and E K Hyde ldquoSodium borohydride itshydrolysis and its use as a reducing agent and in the generationof hydrogenrdquo Journal of the American Chemical Society vol 75no 1 pp 215ndash219 1953
Journal of Fuels 9
[6] S C Amendola P Onnerud M T Kelly P J Petillo S LSharp-Goldman and M Binder ldquoNovel high power densityborohydride-air cellrdquo Journal of Power Sources vol 84 no 1 pp130ndash133 1999
[7] B H Liu and Z P Li ldquoCurrent status and progress of directborohydride fuel cell technology developmentrdquo Journal ofPower Sources vol 187 no 2 pp 291ndash297 2009
[8] B H Liu and Z P Li ldquoA review hydrogen generation fromborohydride hydrolysis reactionrdquo Journal of Power Sources vol187 no 2 pp 527ndash534 2009
[9] B Weng Z Wu Z Li H Yang and H Leng ldquoHydrogengeneration from noncatalytic hydrolysis of LiBH4NH3BH3mixture for fuel cell applicationsrdquo International Journal ofHydrogen Energy vol 36 no 17 pp 10870ndash10876 2011
[10] A E Sanli I Kayacan B Z Uysal and M L Aksu ldquoRecoveryof borohydride from metaborate solution using a silver catalystfor application of direct rechargable borohydrideperoxide fuelcellsrdquo Journal of Power Sources vol 195 no 9 pp 2604ndash26072010
[11] R Jamard J Salomon A Martinent-Beaumont and CCoutanceau ldquoLife time test in direct borohydride fuel cellsystemrdquo Journal of Power Sources vol 193 no 2 pp 779ndash7872009
[12] J-H Wee ldquoA comparison of sodium borohydride as a fuel forproton exchange membrane fuel cells and for direct borohy-dride fuel cellsrdquo Journal of Power Sources vol 155 no 2 pp329ndash339 2006
[13] A V Churikov K V Zapsis V V Khramkov M A ChurikovM P Smotrov and I A Kazarinov ldquoPhase diagrams of theternary systems NaBH
4
+ NaOH + H2
O KBH4
+ KOH + H2
ONaBO
2
+ NaOH + H2
O and KBO2
+ KOH + H2
O at minus10∘CrdquoJournal of Chemical and Engineering Data vol 56 no 1 pp 9ndash13 2011
[14] A V Churikov K V Zapsis V V Khramkov M A Churikovand I M Gamayunova ldquoTemperature-induced transformationof the phase diagrams of ternary systems NaBO
2
+ NaOH+ H2
O and KBO2
+ KOH + H2
Ordquo Journal of Chemical andEngineering Data vol 56 no 3 pp 383ndash389 2011
[15] A V Churikov K V Zapsis A V Ivanishchev and V OSychova ldquoTemperature-induced transformation of the phasediagrams of ternary systems NaBH
4
+ NaOH +H2
O and KBH4
+ KOH + H2
Ordquo Journal of Chemical and Engineering Data vol56 no 5 pp 2543ndash2552 2011
[16] G Rostamikiaa and M J Janik ldquoDirect borohydride oxidationmechanism determination and design of alloy catalysts guidedby density functional theoryrdquo Energy amp Environmental Sciencevol 3 pp 1262ndash1274 2010
[17] B Sljuki J Miliki D M F Santosa and C A C SequeiraldquoCarbon-supported Pt
075
M025
(M = Ni or Co) electrocatalystsfor borohydride oxidationrdquo Electrochim Acta vol 107 pp 577ndash583 2013
[18] B H Liu J Q Yang and Z P Li ldquoConcentration ratio of[OHminus][BH
4
minus] a controlling factor for the fuel efficiency ofborohydride electro-oxidationrdquo International Journal of Hydro-gen Energy vol 34 no 23 pp 9436ndash9443 2009
[19] A V Churikov A V Ivanishchev I M Gamayunova andA V Ushakov ldquoDensity calculations for (Na K)BH
4
+ (NaK)BO
2
+ (Na K)OH + H2
O solutions used in hydrogen powerengineeringrdquo Journal of Chemical and Engineering Data vol 56no 11 pp 3984ndash3993 2011
[20] A V Churikov V O Romanova M A Churikov and I MGamayunova ldquoThemodel of fuel transformation at discharge of
direct borohydride fuel cellrdquo International Review of ChemicalEngineering vol 4 pp 263ndash268 2012
[21] A V Churikov I M Gamayunova K V Zapsis M AChurikov and A V Ivanishchev ldquoInfluence of temperature andalkalinity on the hydrolysis rate of borohydride ions in aqueoussolutionrdquo International Journal of Hydrogen Energy vol 37 no1 pp 335ndash344 2012
[22] Z P Li B H Liu K Arai and S Suda ldquoA fuel cell developmentfor using borohydrides as the fuelrdquo Journal of the Electrochemi-cal Society vol 150 no 7 pp A868ndashA872 2003
[23] Y Wang P Hea and H Zhou ldquoA novel direct borohydridefuel cell using an acid-alkaline hybrid electrolyterdquo Energy ampEnvironmental Science vol 3 no 10 pp 1515ndash1518 2010
[24] J Ma N A Choudhury and Y Sahai ldquoA comprehensive reviewof direct borohydride fuel cellsrdquo Renewable and SustainableEnergy Reviews vol 14 no 1 pp 183ndash199 2010
[25] R Bruhlmann and L Piatti ldquoAn improved method for thetitrimetric determination of boron in ironrdquo Chimia vol 11 p203 1957
[26] A Keshan and C Bimba ldquoCobalt-potassium and ammonium-cobalt dodecaboraterdquo Izvestiya Akademii Nauk Latvijskoj SSRp 115 1954
[27] J Czakow T Steciak and O Szczebinska ldquoThe spectral deter-mination of trace amounts of impurities in the solutions withthe metal electrodes in the spark moderdquo Analytical Chemistryvol 3 p 745 1958
[28] R Rosotti ldquoA fast method for the determination of traceamounts of boron in the steelrdquo Analytical Chemistry vol 44 p208 1962
[29] J Varka and A Sklaf ldquoApplication of potentiometric titrationIV Determination of B
2
O3
in glass enamels and boron-containing raw materialsrdquo Keramik vol 7 p 12 1957
[30] D E Williams and J Vilamis ldquoStability of the curcumincomplex in boron determinationrdquoAnalytical Chemistry vol 33pp 1098ndash1100 1961
[31] S Kertes and M Lederer ldquoPaper chromatography of inorganicions Rf values in mixtures of butanol and Hbrrdquo AnalyticaChimica Acta vol 15 no C pp 543ndash547 1956
[32] A A Nemodruk and Z K Karalova The Analytical Chemistryof Boron Nauka 1964
[33] C A Parker ldquoRaman spectra in spectrofluorimetryrdquo The Ana-lyst vol 84 no 1000 pp 446ndash453 1959
[34] C A Parker and W J Barnes ldquoFluorimetric determination ofboron application to silicon sea water and steelrdquo The Analystvol 85 no 1016 pp 828ndash838 1960
[35] M V Akhmanova Methods of Determination and Analysis ofRear Elements Izdat Akademija Nauk SSSR 1961
[36] E H Jensen A Study on Sodium Borohydride Nyt NordiskForlag Amold Busck Copenhagen Denmark 1954
[37] I Fatt and M Tashima Alkali Metal Dispersions D VanNostrand Co Inc Princeton NJ USA 1961
[38] DA Lyttle EH Jensen andWA Struck ldquoA simple volumetricassay for sodium borohydriderdquo Analytical Chemistry vol 24no 11 pp 1843ndash1844 1952
[39] P K Norkus ldquoIodometric determination of borohydriderdquoRussian Journal of Analytical Chemistry vol 23 pp 908ndash9111968
[40] N N Malrsquoceva and V S Khain Sodium Borohydride Propertiesand Application Nauka 1985
10 Journal of Fuels
[41] C Harzdorf and O Steinhauser ldquoZur photometrisehen Titra-tion von Fluorid mit Thoriumnitratrdquo Freseniusrsquo Zeitschrift furAnalytische Chemie vol 210 no 2 pp 106ndash112 1965
[42] W D Davis L S Mason and G Stegeman ldquoThe heats offormation of sodium borohydride lithium borohydride andlithium aluminum hydriderdquo Journal of the American ChemicalSociety vol 71 no 8 pp 2775ndash2781 1949
[43] S W Chaikin ldquoDirect volumetric assay of sodium borohydrideand potassium borohydriderdquo Analytical Chemistry vol 25 no5 pp 831ndash832 1953
[44] U Ulku and G Somer ldquoDetermination of trace borohydride inbasic solutions using differential pulse polarographyrdquo TurkishJournal of Chemistry vol 33 pp 657ndash665 2009
[45] H Celikkan H Aydin and M L Aksu ldquoThe electroanalyticaldetermination of sodium borohydride using a gold electroderdquoTurkish Journal of Chemistry vol 29 pp 519ndash524 2005
[46] M V Mirkin and A J Bard ldquoVoltammetric method forthe determination of borohydride concentration in alkalineaqueous solutionsrdquoAnalytical Chemistry vol 63 no 5 pp 532ndash533 1991
[47] D M F Santos and C A C Sequeira ldquoPotentiometric moni-toring of sodium borohydride in aqueous solutionsrdquo Ciencia sTecnologia dos Materials vol 20 no 3-4 pp 31ndash34 2008
[48] D M F Santos and C A C Sequeira ldquoSodium borohydridedetermination by measurement of open circuit potentialsrdquoJournal of Electroanalytical Chemistry vol 627 pp 1ndash8 2009
[49] H C Brown and A C Boyd Jr ldquoArgentimetric procedure forborohydride determinationrdquo Analytical Chemistry vol 27 no1 pp 156ndash158 1955
[50] V B Breicis A O Berzina and L K Lepin ldquoPotentiomet-ric titration of water solutions of sodium borohydride byhydrochloric acidrdquo Scientific Short Letter of Riga PolytechnicInstitute vol 15 pp 179ndash188 19651966
[51] U U Lurie Handbook on Analytical Chemistry Khimiya 1979[52] R A Lidin L L Andreeva and V A Molochko Hand-
book of Inorganic Chemistry Constants of Inorganic SubstancesKhimiya 1987
[53] R A Robinson and R H Stokes Electrolyte Solutions the Mea-surement and Interpretation of Conductance Chemical Potentialand Diffusion in Solutions of Simple Electrolytes ButterworthsLondon UK 1959
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
CombustionJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
StructuresJournal of
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear InstallationsScience and Technology of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Solar EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Wind EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear EnergyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Journal of Fuels 9
[6] S C Amendola P Onnerud M T Kelly P J Petillo S LSharp-Goldman and M Binder ldquoNovel high power densityborohydride-air cellrdquo Journal of Power Sources vol 84 no 1 pp130ndash133 1999
[7] B H Liu and Z P Li ldquoCurrent status and progress of directborohydride fuel cell technology developmentrdquo Journal ofPower Sources vol 187 no 2 pp 291ndash297 2009
[8] B H Liu and Z P Li ldquoA review hydrogen generation fromborohydride hydrolysis reactionrdquo Journal of Power Sources vol187 no 2 pp 527ndash534 2009
[9] B Weng Z Wu Z Li H Yang and H Leng ldquoHydrogengeneration from noncatalytic hydrolysis of LiBH4NH3BH3mixture for fuel cell applicationsrdquo International Journal ofHydrogen Energy vol 36 no 17 pp 10870ndash10876 2011
[10] A E Sanli I Kayacan B Z Uysal and M L Aksu ldquoRecoveryof borohydride from metaborate solution using a silver catalystfor application of direct rechargable borohydrideperoxide fuelcellsrdquo Journal of Power Sources vol 195 no 9 pp 2604ndash26072010
[11] R Jamard J Salomon A Martinent-Beaumont and CCoutanceau ldquoLife time test in direct borohydride fuel cellsystemrdquo Journal of Power Sources vol 193 no 2 pp 779ndash7872009
[12] J-H Wee ldquoA comparison of sodium borohydride as a fuel forproton exchange membrane fuel cells and for direct borohy-dride fuel cellsrdquo Journal of Power Sources vol 155 no 2 pp329ndash339 2006
[13] A V Churikov K V Zapsis V V Khramkov M A ChurikovM P Smotrov and I A Kazarinov ldquoPhase diagrams of theternary systems NaBH
4
+ NaOH + H2
O KBH4
+ KOH + H2
ONaBO
2
+ NaOH + H2
O and KBO2
+ KOH + H2
O at minus10∘CrdquoJournal of Chemical and Engineering Data vol 56 no 1 pp 9ndash13 2011
[14] A V Churikov K V Zapsis V V Khramkov M A Churikovand I M Gamayunova ldquoTemperature-induced transformationof the phase diagrams of ternary systems NaBO
2
+ NaOH+ H2
O and KBO2
+ KOH + H2
Ordquo Journal of Chemical andEngineering Data vol 56 no 3 pp 383ndash389 2011
[15] A V Churikov K V Zapsis A V Ivanishchev and V OSychova ldquoTemperature-induced transformation of the phasediagrams of ternary systems NaBH
4
+ NaOH +H2
O and KBH4
+ KOH + H2
Ordquo Journal of Chemical and Engineering Data vol56 no 5 pp 2543ndash2552 2011
[16] G Rostamikiaa and M J Janik ldquoDirect borohydride oxidationmechanism determination and design of alloy catalysts guidedby density functional theoryrdquo Energy amp Environmental Sciencevol 3 pp 1262ndash1274 2010
[17] B Sljuki J Miliki D M F Santosa and C A C SequeiraldquoCarbon-supported Pt
075
M025
(M = Ni or Co) electrocatalystsfor borohydride oxidationrdquo Electrochim Acta vol 107 pp 577ndash583 2013
[18] B H Liu J Q Yang and Z P Li ldquoConcentration ratio of[OHminus][BH
4
minus] a controlling factor for the fuel efficiency ofborohydride electro-oxidationrdquo International Journal of Hydro-gen Energy vol 34 no 23 pp 9436ndash9443 2009
[19] A V Churikov A V Ivanishchev I M Gamayunova andA V Ushakov ldquoDensity calculations for (Na K)BH
4
+ (NaK)BO
2
+ (Na K)OH + H2
O solutions used in hydrogen powerengineeringrdquo Journal of Chemical and Engineering Data vol 56no 11 pp 3984ndash3993 2011
[20] A V Churikov V O Romanova M A Churikov and I MGamayunova ldquoThemodel of fuel transformation at discharge of
direct borohydride fuel cellrdquo International Review of ChemicalEngineering vol 4 pp 263ndash268 2012
[21] A V Churikov I M Gamayunova K V Zapsis M AChurikov and A V Ivanishchev ldquoInfluence of temperature andalkalinity on the hydrolysis rate of borohydride ions in aqueoussolutionrdquo International Journal of Hydrogen Energy vol 37 no1 pp 335ndash344 2012
[22] Z P Li B H Liu K Arai and S Suda ldquoA fuel cell developmentfor using borohydrides as the fuelrdquo Journal of the Electrochemi-cal Society vol 150 no 7 pp A868ndashA872 2003
[23] Y Wang P Hea and H Zhou ldquoA novel direct borohydridefuel cell using an acid-alkaline hybrid electrolyterdquo Energy ampEnvironmental Science vol 3 no 10 pp 1515ndash1518 2010
[24] J Ma N A Choudhury and Y Sahai ldquoA comprehensive reviewof direct borohydride fuel cellsrdquo Renewable and SustainableEnergy Reviews vol 14 no 1 pp 183ndash199 2010
[25] R Bruhlmann and L Piatti ldquoAn improved method for thetitrimetric determination of boron in ironrdquo Chimia vol 11 p203 1957
[26] A Keshan and C Bimba ldquoCobalt-potassium and ammonium-cobalt dodecaboraterdquo Izvestiya Akademii Nauk Latvijskoj SSRp 115 1954
[27] J Czakow T Steciak and O Szczebinska ldquoThe spectral deter-mination of trace amounts of impurities in the solutions withthe metal electrodes in the spark moderdquo Analytical Chemistryvol 3 p 745 1958
[28] R Rosotti ldquoA fast method for the determination of traceamounts of boron in the steelrdquo Analytical Chemistry vol 44 p208 1962
[29] J Varka and A Sklaf ldquoApplication of potentiometric titrationIV Determination of B
2
O3
in glass enamels and boron-containing raw materialsrdquo Keramik vol 7 p 12 1957
[30] D E Williams and J Vilamis ldquoStability of the curcumincomplex in boron determinationrdquoAnalytical Chemistry vol 33pp 1098ndash1100 1961
[31] S Kertes and M Lederer ldquoPaper chromatography of inorganicions Rf values in mixtures of butanol and Hbrrdquo AnalyticaChimica Acta vol 15 no C pp 543ndash547 1956
[32] A A Nemodruk and Z K Karalova The Analytical Chemistryof Boron Nauka 1964
[33] C A Parker ldquoRaman spectra in spectrofluorimetryrdquo The Ana-lyst vol 84 no 1000 pp 446ndash453 1959
[34] C A Parker and W J Barnes ldquoFluorimetric determination ofboron application to silicon sea water and steelrdquo The Analystvol 85 no 1016 pp 828ndash838 1960
[35] M V Akhmanova Methods of Determination and Analysis ofRear Elements Izdat Akademija Nauk SSSR 1961
[36] E H Jensen A Study on Sodium Borohydride Nyt NordiskForlag Amold Busck Copenhagen Denmark 1954
[37] I Fatt and M Tashima Alkali Metal Dispersions D VanNostrand Co Inc Princeton NJ USA 1961
[38] DA Lyttle EH Jensen andWA Struck ldquoA simple volumetricassay for sodium borohydriderdquo Analytical Chemistry vol 24no 11 pp 1843ndash1844 1952
[39] P K Norkus ldquoIodometric determination of borohydriderdquoRussian Journal of Analytical Chemistry vol 23 pp 908ndash9111968
[40] N N Malrsquoceva and V S Khain Sodium Borohydride Propertiesand Application Nauka 1985
10 Journal of Fuels
[41] C Harzdorf and O Steinhauser ldquoZur photometrisehen Titra-tion von Fluorid mit Thoriumnitratrdquo Freseniusrsquo Zeitschrift furAnalytische Chemie vol 210 no 2 pp 106ndash112 1965
[42] W D Davis L S Mason and G Stegeman ldquoThe heats offormation of sodium borohydride lithium borohydride andlithium aluminum hydriderdquo Journal of the American ChemicalSociety vol 71 no 8 pp 2775ndash2781 1949
[43] S W Chaikin ldquoDirect volumetric assay of sodium borohydrideand potassium borohydriderdquo Analytical Chemistry vol 25 no5 pp 831ndash832 1953
[44] U Ulku and G Somer ldquoDetermination of trace borohydride inbasic solutions using differential pulse polarographyrdquo TurkishJournal of Chemistry vol 33 pp 657ndash665 2009
[45] H Celikkan H Aydin and M L Aksu ldquoThe electroanalyticaldetermination of sodium borohydride using a gold electroderdquoTurkish Journal of Chemistry vol 29 pp 519ndash524 2005
[46] M V Mirkin and A J Bard ldquoVoltammetric method forthe determination of borohydride concentration in alkalineaqueous solutionsrdquoAnalytical Chemistry vol 63 no 5 pp 532ndash533 1991
[47] D M F Santos and C A C Sequeira ldquoPotentiometric moni-toring of sodium borohydride in aqueous solutionsrdquo Ciencia sTecnologia dos Materials vol 20 no 3-4 pp 31ndash34 2008
[48] D M F Santos and C A C Sequeira ldquoSodium borohydridedetermination by measurement of open circuit potentialsrdquoJournal of Electroanalytical Chemistry vol 627 pp 1ndash8 2009
[49] H C Brown and A C Boyd Jr ldquoArgentimetric procedure forborohydride determinationrdquo Analytical Chemistry vol 27 no1 pp 156ndash158 1955
[50] V B Breicis A O Berzina and L K Lepin ldquoPotentiomet-ric titration of water solutions of sodium borohydride byhydrochloric acidrdquo Scientific Short Letter of Riga PolytechnicInstitute vol 15 pp 179ndash188 19651966
[51] U U Lurie Handbook on Analytical Chemistry Khimiya 1979[52] R A Lidin L L Andreeva and V A Molochko Hand-
book of Inorganic Chemistry Constants of Inorganic SubstancesKhimiya 1987
[53] R A Robinson and R H Stokes Electrolyte Solutions the Mea-surement and Interpretation of Conductance Chemical Potentialand Diffusion in Solutions of Simple Electrolytes ButterworthsLondon UK 1959
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
CombustionJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
StructuresJournal of
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear InstallationsScience and Technology of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Solar EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Wind EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear EnergyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
10 Journal of Fuels
[41] C Harzdorf and O Steinhauser ldquoZur photometrisehen Titra-tion von Fluorid mit Thoriumnitratrdquo Freseniusrsquo Zeitschrift furAnalytische Chemie vol 210 no 2 pp 106ndash112 1965
[42] W D Davis L S Mason and G Stegeman ldquoThe heats offormation of sodium borohydride lithium borohydride andlithium aluminum hydriderdquo Journal of the American ChemicalSociety vol 71 no 8 pp 2775ndash2781 1949
[43] S W Chaikin ldquoDirect volumetric assay of sodium borohydrideand potassium borohydriderdquo Analytical Chemistry vol 25 no5 pp 831ndash832 1953
[44] U Ulku and G Somer ldquoDetermination of trace borohydride inbasic solutions using differential pulse polarographyrdquo TurkishJournal of Chemistry vol 33 pp 657ndash665 2009
[45] H Celikkan H Aydin and M L Aksu ldquoThe electroanalyticaldetermination of sodium borohydride using a gold electroderdquoTurkish Journal of Chemistry vol 29 pp 519ndash524 2005
[46] M V Mirkin and A J Bard ldquoVoltammetric method forthe determination of borohydride concentration in alkalineaqueous solutionsrdquoAnalytical Chemistry vol 63 no 5 pp 532ndash533 1991
[47] D M F Santos and C A C Sequeira ldquoPotentiometric moni-toring of sodium borohydride in aqueous solutionsrdquo Ciencia sTecnologia dos Materials vol 20 no 3-4 pp 31ndash34 2008
[48] D M F Santos and C A C Sequeira ldquoSodium borohydridedetermination by measurement of open circuit potentialsrdquoJournal of Electroanalytical Chemistry vol 627 pp 1ndash8 2009
[49] H C Brown and A C Boyd Jr ldquoArgentimetric procedure forborohydride determinationrdquo Analytical Chemistry vol 27 no1 pp 156ndash158 1955
[50] V B Breicis A O Berzina and L K Lepin ldquoPotentiomet-ric titration of water solutions of sodium borohydride byhydrochloric acidrdquo Scientific Short Letter of Riga PolytechnicInstitute vol 15 pp 179ndash188 19651966
[51] U U Lurie Handbook on Analytical Chemistry Khimiya 1979[52] R A Lidin L L Andreeva and V A Molochko Hand-
book of Inorganic Chemistry Constants of Inorganic SubstancesKhimiya 1987
[53] R A Robinson and R H Stokes Electrolyte Solutions the Mea-surement and Interpretation of Conductance Chemical Potentialand Diffusion in Solutions of Simple Electrolytes ButterworthsLondon UK 1959
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
CombustionJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
StructuresJournal of
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear InstallationsScience and Technology of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Solar EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Wind EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear EnergyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
TribologyAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
FuelsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal ofPetroleum Engineering
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Industrial EngineeringJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Advances in
CombustionJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Renewable Energy
Submit your manuscripts athttpwwwhindawicom
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
StructuresJournal of
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Hindawi Publishing Corporation httpwwwhindawicom Volume 2014
International Journal ofPhotoenergy
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear InstallationsScience and Technology of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Solar EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Wind EnergyJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Nuclear EnergyInternational Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
High Energy PhysicsAdvances in
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
![The question of determination of grain size in …...In standards GOST 5639-82 [1], ISO 643:2012 [2] for determination of grain size, grains of metals are separate crystals of polycrystalline](https://static.fdocuments.in/doc/165x107/5f08ecf27e708231d4246406/the-question-of-determination-of-grain-size-in-in-standards-gost-5639-82-1.jpg)
