Research Article Effects of E-Beam Irradiation on the...

Research ArticleEffects of E-Beam Irradiation on the ChemicalPhysical and Electrochemical Properties of Activated Carbonsfor Electric Double-Layer Capacitors

Min-Jung Jung Mi-Seon Park and Young-Seak Lee

Department of Applied Chemistry and Biological Engineering Chungnam National University Daejeon 305-764 Republic of Korea

Correspondence should be addressed to Young-Seak Lee youngsleecnuackr

Received 5 March 2015 Accepted 27 March 2015

Academic Editor Jae-Ho Kim

Copyright copy 2015 Min-Jung Jung 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

Activated carbons (ACs) were modified via e-beam irradiation at various doses for use as an electrode material in electric double-layer capacitors (EDLCs) The chemical compositions of the AC surfaces were largely unchanged by the e-beam irradiation TheACs treated with the e-beam at radiation doses of 200 kGy exhibited higher nanocrystallinity than the untreated ACs The specificsurface areas and pore volumes of the e-beam irradiated ACs were also higher than those of the untreated ACs These resultswere attributed to the transformation and degradation of the nanocrystallinity of the AC surfaces due to the e-beam irradiationThe specific capacitance of the ACs treated with the e-beam at radiation doses of 200 kGy increased by 24 compared with theuntreated ACs and the charge transfer resistance of the ACs was decreased by the e-beam irradiation The enhancement of theelectrochemical properties of the e-beam irradiated ACs can be attributed to an increase in their specific surface area and surfacecrystallinity

1 Introduction

Electron-beam (e-beam) irradiation has been of interestin many research fields such as polymerization and themodification of polymers lithography and food science[1ndash5] Electron-beam irradiation changes the structures ofpolymer chains which induce chain scission cross-linkingor radical formation [6ndash8] Recently some researchers haveattempted to apply e-beam irradiation to various carbonmaterials (sp3 or sp2 materials) such as carbon nanotubesgraphene and diamond [9ndash11] It is usually intended tostudy a damage or deposition of carbon materials dur-ing analyzing by equipment using the e-beam includingscanning electron microscopy (SEM) transmission electronmicroscopy (TEM) focused ion beam (FIB) and atomic forcemicroscopy (AFM) [12ndash14] Generally e-beam irradiationcauses the hemolytic cleavage of C-C and C-H bonds onpolymer surfaces The resulting alkyl radicals are not stableand undergo a complex series of reactions that lead to cross-linking chain scissions oxidation and the formation of

C=C bonds [15] E-beam irradiation is a simple solvent-freeand ambient-temperature electron-beam-basedmodificationmethod [16]Therefore it is expected that e-beam irradiationis a viable technology for the modification of carbon materialsurfaces for electrochemical applications such as electricaldouble-layer capacitors (EDLCs)

In this study e-beam irradiation was applied to modifyactivated carbons (ACs) for use as electrode materials inEDLCs The changes in the physical and chemical propertiesof the AC surfaces after modification were characterized andanalyzed and the effects of e-beam irradiation on the elec-trochemical performance of the ACs were also investigatedThrough this study the potential use of the electron-beamirradiation was evaluated

2 Materials and Methods

21 E-Beam Irradiation of Activated Carbons In this studyphenol-based AC (MSP-20 Kansai Coke and Chemicals CoLtd Japan) was used For the e-beam treatment 2 g of the

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2015 Article ID 240264 8 pageshttpdxdoiorg1011552015240264

2 Journal of Nanomaterials

AC was poured into sample bottles The sample bottles wereplaced on a tray for e-beam radiation E-beam irradiationwas performed at 100 200 300 and 500 kGy The preparedsamples were named according to the e-beam radiation doseas E100-AC E200-AC E300-AC and E500-AC and theuntreated AC was named R-AC

22 Physicochemical Characterization To investigate thechanges in the functional groups on the surfaces of theuntreated and e-beam irradiated ACs X-ray photoelectronspectroscopy (XPS VGMultilab 2000ThermoVGScientificUK) analysis was performed using Al K120572 radiation XPS ele-mental analysis was used to determine the average elementalcontents in the sample The C1s peaks were deconvolutedinto several pseudo-Voigt functions (sums of a Gaussian-Lorentzian function) using a peak analysis program obtainedfrom Unipress Co USA The pseudo-Voigt function is givenby [17]

119865 (119864) = 119867[(1 minus 119878) exp(minus ln (2) (119864 minus 119864

0

119877FWHM)

2

)

+

119878

1 + ((119864 minus 1198640) 119877FWHM)

2]

(1)

where 119865(119864) is the intensity at energy 119864 119867 is the peakheight 119864

0is the peak center 119877FWHM is the full width at half-

maximum (FWHM) and 119878 is the shape function related tothe symmetry and the Gaussian-Lorentzianmixing ratioTheFWHM of the C1s peak was 13 eV

To characterize the crystalline structure of the ACsthe Raman spectra were recorded using a HORIBA Jobin-Yvon LabRam Aramis spectrometer (HORIBA Jobin-YvonEdison NJ) The 514 nm arrow of an Ar-ion laser was usedas the excitation source The G and D peak positions and the119868D119868G intensity ratio arewidely used for identifying the type ofcarbon and characterizing the carbon structureThe resultingRaman spectra were deconvoluted into G and D bands usingGaussian functions

The pore structures of the samples were assessed usingN2adsorption at 77K (ASAP2020 Micromeritics USA)The

specific surface areas of the samples were evaluated usingthe Brunauer-Emmett-Teller (BET) equation In addition thepore size distributions of the samples were determined usingdensity functional theory (DFT)

23 Electrochemical Characterization EDLC electrodes werefabricated by mixing 80wt AC 10wt carbon black(Super P Timcal Ltd Switzerland) and a 10wt solu-tion of polyvinylidene fluoride (PVDF Aldrich USA) inN-methyl pyrrolidone (NMP Aldrich USA) to form aslurry which was then painted onto a titanium plate TheAC-based electrodes were electrochemically characterizedusing a computer-controlled potentiostatgalvanostat (IviumTechnologies Netherlands) equipped with a three-electrodeassembly The AC-based electrode was used as the workingelectrode and Ag|AgCl was used as the reference electrodeA platinum plate was used as the counter electrode Cyclic

Inte

nsity

1000 800 600 400 200

R-AC E100-ACE200-AC E300-ACE500-AC

Binding energy (eV)

Figure 1 XPS wide scan spectra of e-beam irradiated ACs

Table 1 XPS surface elemental analysis parameters of e-beamirradiated ACs

Sample Elemental contents (atomic percent) OC ()C O

R-AC 927 73 787E100-AC 934 66 707E200-AC 929 71 764E300-AC 933 67 718E500-AC 937 63 672

voltammetry (CV) of the electrode materials was performedover a potential range of 0 to 1 V at scan rates of 5 and50mV sminus1 in a 1M H

2SO4electrolyte

An AC impedance spectrum analyzer was employedto measure and analyze the impedance behavior of thecapacitors In this work themeasurements were conducted at0V with an AC potential amplitude of 5mV in the frequencyrange of 10mHz to 100 kHz

3 Results and Discussion

31 Changes in the Surface Chemical Properties of the E-Beam Irradiated Activated Carbons XPS elemental analysiswas conducted to compare the surface chemical propertiesof the ACs before and after e-beam irradiation As canbe observed in Table 1 and Figure 1 two main peaks areidentified marked C1s and O1s The peaks at approximately970ndash1 000 eV are the oxygenAuger peaks [18 19] As shown inTable 1 the samples are almost identical in terms of elementalcomposition The oxygen content of R-AC was found to beapproximately 73 at while the e-beam irradiated ACs hadoxygen contents of 63ndash71 atTherefore it is concluded thate-beam irradiation does not have a significant effect on thechemical composition of the AC surfaces

Journal of Nanomaterials 3

Table 2 C1s peak parameters of e-beam irradiated ACs

Component Peak position (eV) Concentration ()R-AC E100-AC E200-AC E300-AC E500-AC

C(1)CndashC (sp2) 2845 641 732 746 703 663

C(2)CndashC (sp3) 2854 199 165 119 184 239

C(3)CndashO 2864 118 75 104 83 77

C(4)C=O 2874 42 28 31 30 21

Table 3 Structure characteristics of e-beam irradiated ACs obtained by the Raman spectra deconvolution

Intensity ratio119871119886

119868D1119868G1 119868D2119868G2 119868G2119868G1

R-AC 186 116 248 236E200-AC 154 096 236 285E500-AC 175 124 185 251

In particular to investigate the changes in the chemicalbonds of the ACs due to e-beam irradiation untreated and e-beam irradiated ACs were analyzed using C1s deconvolutionThe deconvolution results of the C1s peaks are shown inFigure 2The C1s peaks of all samples were deconvoluted intofour peaks at 2845 2854 2864 and 2874 eV which corre-spond to C-C (sp2) C-C (sp3) C-O and C=O respectively[20]The components peak positions and concentrations arealso summarized in Table 2 In this study E200-AC had thehighest concentration of C-C sp2 bonds The concentrationof C-C sp2 bonds on the AC surfaces increased with e-beamirradiation up to 200 kGy while the concentration of C-Csp3 bonds on the AC surfaces decreased In contrast whenthe e-beam irradiation was performed at above 200 kGy theconcentration of C-C sp2 bonds decreased and the C-C sp3bonds increased Thus e-beam irradiation transformed anddegraded the nanocrystals on the AC surfaces [21]

The Raman spectra were deconvoluted to acquire infor-mation about the changes in the carbon structure of the ACsdue to e-beam irradiation and are shown in Figure 3 TheRaman spectra for the ACs were almost similar thereforeonly the Raman spectra of R-AC E200-AC and E500-ACare shown in Figure 3 Four peaks were observed at approxi-mately 1605 cmminus1 (G1) 1530 cmminus1 (G2) 1340ndash1355 cmminus1 (D1)and 1280 cmminus1 (D2) The D-peaks (D1 and D2) correspondto the amorphous domains while the G-peaks (G1 and G2)correspond to the graphite domains The peak at 1605 cmminus1(G band) is attributed to the typical C-C stretching modesin graphite The peak observed at approximately 1340ndash1355 cmminus1 was assigned to the D band (related to the defectsand disorder in the carbon material) which is typical fordisordered carbon [22] The Raman spectra of R-AC E200-AC and E500-ACwere almost identical however the Ramanspectra of E200-AC had a more intense G1 peak than R-ACand E500-AC

Table 3 shows the peak intensity ratios of 119868D1119868G1 119868D2119868G2119868G2119868G1 and 119871119886 in the investigated spectral range whichprovides important information about the structures of thecarbon materials [20] Based on the following equation thecrystalline size (119871

119886) was calculated [23]

119871119886= 44 times (

119868D1119868G1)

minus1

(2)

It is commonly known that a lower 119868D2119868G2 ratio indicatesa lower amorphous phase content in the carbon materialwhereas a lower 119868G2119868G1 ratio indicates decreasing of thecarbon in forms of clusters [24] According to the Ramanresults E200-AC contained the smallest amount of amor-phous phase

For the e-beam energies employed in this study the pri-mary effect of irradiation in graphitic or sp2 carbonmaterialsis a result of the knock-on collisions of atoms with electronswhich generates vacancies and structural defects (or inter-stitials) [25] In addition the materials are far from thermalequilibrium that is to say nonequilibrium and under cer-tain circumstances they can fulfill the conditions for self-organized structure formation Accordingly the change inhybridization facilitates the structural transformation sp2+120575sp3 harr sp2 sp2+120575 (trigonal harr mixed trigonal tetrahedral)[26]Therefore the nanocrystallinity of the AC surface couldbe increased by e-beam irradiation

32 Changes in the Textural Properties of E-Beam Irradi-ated Activated Carbons Nitrogen adsorption analysis wasperformed at 77K to examine the changes in the poretexture of the ACs after e-beam irradiation at differentradiation doses Table 4 provides detailed information aboutthe textural properties of the e-beam irradiated ACs It wasobserved that the specific surface area and total pore volume


290 288 286 284 2820

1000

2000

3000

4000

5000

6000

Inte

nsity

Binding energy (eV)

C(1)

C(2)

C(3)C(4)

(a)

290 288 286 284 2820

1000

2000

3000

4000

5000

6000

Inte

nsity

Binding energy (eV)

C(1)

C(2)C(3)

C(4)

(b)

0

1000

2000

3000

4000

5000

6000

Inte

nsity

290 288 286 284 282Binding energy (eV)

C(1)

C(2)C(3)

C(4)

(c)

290 288 286 284 2820

1000

2000

3000

4000

5000

6000In

tens

ity

Binding energy (eV)

C(1)

C(2)

C(3)C(4)

(d)

0

1000

2000

3000

4000

5000

6000

Inte

nsity


C(1)

C(2)

C(3)C(4)

(e)

Figure 2 Deconvolution of the core level C1s spectra of (a) R-AC (b) E100-AC (c) E200-AC (d) E300-AC and (e) E500-AC


Table 4 Textual properties of e-beam irradiated ACs

Sample Specific surface area (m2g) Total pore volume (cm3g) Micropore volume (cm3g) Mesopore volume (cm3g)R-AC 1924 087 076 011E100-AC 2300 092 088 004E200-AC 2339 102 099 003E300-AC 2310 097 096 001E500-AC 1902 082 079 003

2000 1800 1600 1400 1200 1000 800

Inte

nsity

(au

)

G2

G1 D1

D2

Raman shift (cmminus1)

(a)

Inte

nsity

(au

)

G2

G1D1

D2

2000 1800 1600 1400 1200 1000 800Raman shift (cmminus1)

(b)

Inte

nsity

(au

)

G2

G1D1

D2


(c)

Figure 3 Raman spectra of (a) R-AC (b) E200-AC and (c) E500-AC

were higher for the e-beam irradiated ACs than for R-ACexcept for E500-AC E200-AC exhibited the highest specificsurface area and total pore volume (2339m2g and 102 ccgresp) These changes in textural properties indicated thatthe nanocrystallinity of the AC surface was transformed anddegraded by the e-beam irradiation As Raman results inSection 32 119868G2119868G1 ratio of ACs which indicated reductionof carbon in form of clusters was decreased as increase ofe-beam irradiation dose As mentioned above the smaller119868G2119868G1 ratio led to decreasing of the carbon in forms of

clusters [24] It was expected that specific surface area of e-beam irradiated ACs could be changed by degradation ofAC surface The specific surface area of ACs was increasedby appropriate e-beam irradiation dose however excessiveirradiation dose could reduce the specific surface area of ACsdue to collapse of the AC surface

Figure 4 depicts the nitrogen adsorption isotherms ofuntreated and e-beam irradiated ACs The isotherms of allsamples were observed to be type I according to the IUPACclassification [27] However e-beam irradiated ACs seem to


00 02 04 06 08 100

100

200

300

400

500

600

700

R-ACE100-AC

E200-AC

E300-ACE500-AC

Qua

ntity

adso

rbed

(cm

2g

STP

)

Relative pressure (PP0)

Figure 4 Nitrogen adsorption isotherms of e-beam irradiated ACs

1 2 3 4 5000

005

010

015

020

025

R-ACE100-ACE200-AC

E300-ACE500-AC

Pore diameter (nm)

Volu

me (

cm3g

)

Figure 5 DFT pore size distribution of e-beam irradiated ACs

be more microporous than R-AC the adsorption of R-ACgradually increased above a 119875119875

0ratio of 01 Figure 5 shows

the DFT pore size distribution and it can clearly be observedthat all of the samples were microporous In addition E100-AC exhibited a larger pore volume than the other sampleswith pore diameters of 15 to 20 nm In general the per-formances of the AC-based EDLCs were determined by thetextural properties of the ACs [28] Changes in the specificsurface areas pore volumes and pore size distributions of theACs after e-beam irradiation were expected to improve theperformances of the prepared AC-based EDLCs

33 Electrochemical Properties of the E-Beam Irradiated Acti-vated Carbons Cyclic voltammetry (CV) was used to assess

Table 5 Specific capacitances of e-beam irradiated ACs

Sample Specific capacitance (Fg)5mVs 50mVs

R-AC 247 157E100-AC 277 257E200-AC 306 262E300-AC 250 229E500-AC 169 161

the electrochemical properties of the e-beam irradiated AC-based electrodes Figure 6 shows the CV plots of each sampleacquired at scan rates of 5mVs and 50mVs At a scanrate of 5mVs (Figure 6(a)) the CV profiles of the ACswere approximately rectangular and small redox peaks wereobserved at 03ndash04V which indicated the occurrence ofa pseudo-Faradaic reaction caused by oxygen functionalgroups [29] R-AC had the highest redox peaks in this studybecause the C=O bonds in the ACs were reduced by the e-beam irradiation In the CV profiles of the ACs obtained at50mVs (Figure 6(b)) the CVs also exhibited a rectangularshape with small redox peaks

The discharge capacitances (119862) of the electrodes in theEDLCs were calculated using [30]

119862 =

1

119908Δ119881

int

1

0

119894 119889119905 (3)

where 119862 is the specific capacitance of the cell in Fg 119908 is themass of the activematerial 119894 is the current flowing for time 119889119905and Δ119881 is the potential window in which the current flows

The calculated specific capacitances of the AC-based elec-trodes are listed in Table 5 In this study E200-AC exhibitedthe highest specific capacitances (306 and 262 Fg at scan ratesof 5 and 50mVs resp) The specific capacitances of the e-beam irradiated ACs increased with the e-beam irradiationdose up to 200 kGy and then decreased These results wereexpected because the specific surface areas and pore volumesof the ACs were increased by the e-beam irradiation

Figure 7 depicts the results of the AC impedance mea-surements of the prepared AC-based electrodes The chargetransfer resistance (119877

119862) values for R-AC E100-AC E200-AC

E300-AC and E500-AC were calculated to be 180 061 056075 and 384Ω respectively The impedance results directlyshowed that the e-beam irradiation contributed significantlyto the reduction of the charge transfer resistance of theACs which is in agreement with the change in electricalconductivity [31] As mentioned above the nanocrystallinityof the AC surfaces was increased by the e-beam irradiationTherefore it can be concluded that the increased nanocrys-tallinity of the AC surface induced by the e-beam irradiationalso decreased the charge transfer resistance However thecharge transfer resistance of the ACs increased because thenanocrystallinity of the AC surfaces was destroyed by exces-sive e-beam irradiation (E500-AC) The increasing chargetransfer resistance of the e-beam irradiated ACswas expectedbecause of the decrease in the specific capacitanceThe chargetransfer resistance was generally related to the electroactive


00 02 04 06 08 10minus2

minus1

0

1

2Cu

rren

t (m

Am

g)

Voltage (V versus AgAgCl)


(a)

Voltage (V versus AgAgCl)R-AC E100-ACE200-AC E300-ACE500-AC

00 02 04 06 08 10

minus10

minus5

0

5

10

Curr

ent (

mA

mg)

(b)

Figure 6 Cyclic voltammograms of e-beam irradiated ACs obtained at 5mVs (a) and 50mVs (b)

0 4 8 12 16 20 240

4

8

12

16

20

24

R-ACE100-AC

E200-AC

E300-ACE500-AC

0 1 2 3 4 5 6012345

minusZ998400998400

(Ω)

Z998400(Ω)

Figure 7 Nyquist impedance plots of e-beam irradiated ACs in 1MH2SO4in the frequency range from 10mHz to 100 kHz

surface area of the electrode materials The electroactivesurface areawas a combination of the specific surface area andelectrical conductivity [32] R-AC and E500-AC had similarspecific surface area but the charge transfer resistance ofE500-AC is higher than R-AC It was expected that electricalconductivity of E500-AC decreased which causes a reductionin the specific capacitance

4 Conclusions

To investigate the use of e-beam irradiation for the mod-ification of AC surfaces ACs were treated with e-beamirradiation Based on the XPS results the e-beam irradiation

did not affect the chemical compositions of the AC surfaceshowever the C-C sp2 bonds on the AC surfaces increased asa result of the e-beam irradiation According to the Ramanresults the e-beam irradiated ACs contained lower amountsof amorphous material than the untreated AC The specificsurface areas and total pore volumes of the ACs increasedafter the e-beam irradiation These changes in the chemicaland textural properties indicated that the nanocrystallinity oftheAC surfaceswas transformed and degraded by the e-beamirradiation Accordingly the electrochemical properties ofthe ACs were enhanced by the e-beam irradiation Thespecific capacitance of theAC subjected to e-beam irradiationat a dose of 200 kGy increased by 24 relative to theuntreated AC Furthermore the charge transfer resistance ofthis sample decreased from 180 (untreated AC) to 056 uponirradiation Therefore e-beam irradiation could be used tomodify AC surfaces for electrochemical applications

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

This research was supported by the National Research Foun-dation ofKorea (NRF) funded by theMinistry of Science ICTand Future Planning (no 2013M2A2A6043697)

References

[1] R L Clough ldquoHigh-energy radiation and polymers a reviewof commercial processes and emerging applicationsrdquo NuclearInstruments and Methods in Physics Research B Beam Interac-tions with Materials and Atoms vol 185 no 1ndash4 pp 8ndash33 2001


[2] E H Lee ldquoIon-beam modification of polymeric materialsmdashfundamental principles and applicationsrdquo Nuclear Instrumentsand Methods in Physics Research Section B Beam Interactionswith Materials and Atoms vol 151 no 1ndash4 pp 29ndash41 1999

[3] P M Mendes S Jacke K Critchley et al ldquoGold nanoparticlepatterning of siliconwafers using chemical e-beam lithographyrdquoLangmuir vol 20 no 9 pp 3766ndash3768 2004

[4] M C Cabeza L de la Hoz R Velasco M I Cambero and JA Ordonez ldquoSafety and quality of ready-to-eat dry fermentedsausages subjected to E-beam radiationrdquo Meat Science vol 83no 2 pp 320ndash327 2009

[5] M M Hassan R O Aly J A Hasanen and E S F El SayedldquoThe effect of gamma irradiation on mechanical thermal andmorphological properties of glass fiber reinforced polyethylenewastereclaim rubber compositesrdquo Journal of Industrial andEngineering Chemistry vol 20 no 3 pp 947ndash952 2014

[6] R Chosdu N Hilmy T B Erlinda and B Abbas ldquoRadia-tion and chemical pretreatment of cellulosic wasterdquo RadiationPhysics and Chemistry vol 42 no 4ndash6 pp 695ndash698 1993

[7] J Y Jung M S Park M I Kim and Y S Lee ldquoNovelreforming of pyrolized fuel oil by electron beam radiation forpitch productionrdquo Carbon Letters vol 15 no 4 pp 262ndash2672014

[8] J Jung and Y Lee ldquoPreparation of pitch from pyrolized fueloil by electron beam radiation and its melt-electrospinningpropertyrdquo Carbon Letters vol 15 no 2 pp 129ndash135 2014

[9] D Teweldebrhan andAA Balandin ldquoModification of grapheneproperties due to electron-beam irradiationrdquo Applied PhysicsLetters vol 94 no 1 Article ID 013101 2009

[10] W Ding D A Dikin X Chen et al ldquoMechanics of hydro-genated amorphous carbon deposits from electron-beam-induced deposition of a paraffin precursorrdquo Journal of AppliedPhysics vol 98 no 1 Article ID 014905 2005

[11] S Gupta and R J Patel ldquoChanges in the vibrational modes ofcarbon nanotubes induced by electron-beam irradiation reso-nanceRaman spectroscopyrdquo Journal of Raman Spectroscopy vol38 no 2 pp 188ndash199 2007

[12] F Sola ldquoElectrical properties of pristine and electron irradiatedcarbon nanotube yarns at small length scalesrdquo Modern Chem-istry amp Applications vol 2 no 1 p 116 2014

[13] A Qiu and D F Bahr ldquoModification of the mechanicalproperties of carbon nanotube arrays using electron irradiationinduced oxidationrdquoMeccanica vol 50 no 2 pp 575ndash583 2014

[14] S Prawer and R Kalish ldquoIon-beam-induced transformation ofdiamondrdquo Physical Review B vol 51 no 22 pp 15711ndash157221995

[15] M Slouf H Synkova J Baldrian et al ldquoStructural changes ofUHMWPE after e-beam irradiation and thermal treatmentrdquoJournal of Biomedical Materials Research Part B Applied Bioma-terials vol 85 no 1 pp 240ndash251 2008

[16] S H Kim Y J Noh S N Kwon et al ldquoEfficient modification oftransparent graphene electrodes by electron beam irradiationfor organic solar cellsrdquo Journal of Industrial and EngineeringChemistry 2014

[17] L E Cruz-Barba S Manolache and F Denes ldquoNovel plasmaapproach for the synthesis of highly fluorinated thin surfacelayersrdquo Langmuir vol 18 no 24 pp 9393ndash9400 2002

[18] S Yuan S O Pehkonen B Liang Y P Ting K G Neohand E T Kang ldquoSuperhydrophobic fluoropolymer-modifiedcopper surface via surface graft polymerisation for corrosionprotectionrdquoCorrosion Science vol 53 no 9 pp 2738ndash2747 2011

[19] R V Gelamo R Landers F P M Rouxinol et al ldquoXPSinvestigation of plasma-deposited polysiloxane films irradiatedwith helium ionsrdquo Plasma Processes and Polymers vol 4 no 4pp 482ndash488 2007

[20] S Karthikeyan K Viswanathan R Boopathy P Maharaja andG Sekaran ldquoThree dimensional electro catalytic oxidation ofaniline by boron doped mesoporous activated carbonrdquo Journalof Industrial and Engineering Chemistry vol 21 pp 942ndash9502015

[21] F Banhart ldquoIrradiation effects in carbon nanostructuresrdquoReports on Progress in Physics vol 62 no 8 pp 1181ndash1221 1999

[22] J Qiu Y Li Y Wang C Liang T Wang and DWang ldquoA novelform of carbonmicro-balls from coalrdquoCarbon vol 41 no 4 pp767ndash772 2003

[23] Y Zhang Y Tang L Lin and E Zhang ldquoMicrostructuretransformation of carbon nanofibers during graphitizationrdquoTransactions of Nonferrous Metals Society of China vol 18 no5 pp 1094ndash1099 2008

[24] J Srenscek-Nazzal and B Michalkiewicz ldquoThe simplex opti-mization for high porous carbons preparationrdquo Polish Journalof Chemical Technology vol 13 no 4 pp 63ndash70 2011

[25] J Li and F Banhart ldquoThe engineering of hot carbon nanotubeswith a focused electron beamrdquo Nano Letters vol 4 no 6 pp1143ndash1146 2004

[26] S Gupta R J Patel N Smith R E Giedd and D Hui ldquoRoomtemperature dc electrical conductivity studies of electron-beamirradiated carbon nanotubesrdquo Diamond and Related Materialsvol 16 no 2 pp 236ndash242 2007

[27] S J Gregg and K S W Sing Adsorption Surface Area andPorosity Academic Press London UK 2nd edition 1982

[28] O Barbieri M Hahn A Herzog and R Kotz ldquoCapacitancelimits of high surface area activated carbons for double layercapacitorsrdquo Carbon vol 43 no 6 pp 1303ndash1310 2005

[29] S R S Prabaharan R Vimala and Z Zainal ldquoNanostructuredmesoporous carbon as electrodes for supercapacitorsrdquo Journalof Power Sources vol 161 no 1 pp 730ndash736 2006

[30] M Ramani B S Haran R E White and B N PopovldquoSynthesis and characterization of hydrous ruthenium oxide-carbon supercapacitorsrdquo Journal of the Electrochemical Societyvol 148 no 4 pp A374ndashA380 2001

[31] N G Tsierkezos P Szroeder and U Ritter ldquoMulti-walledcarbon nanotubes as electrode materials for electrochemicalstudies of organometallic compounds in organic solventmediardquoMonatshefte fur Chemie vol 142 no 3 pp 233ndash242 2011

[32] M-S Wu and H-H Hsieh ldquoNickel oxidehydroxidenanoplatelets synthesized by chemical precipitation forelectrochemical capacitorsrdquo Electrochimica Acta vol 53 no 8pp 3427ndash3435 2008

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Journal ofNanomaterials


AC was poured into sample bottles The sample bottles wereplaced on a tray for e-beam radiation E-beam irradiationwas performed at 100 200 300 and 500 kGy The preparedsamples were named according to the e-beam radiation doseas E100-AC E200-AC E300-AC and E500-AC and theuntreated AC was named R-AC

22 Physicochemical Characterization To investigate thechanges in the functional groups on the surfaces of theuntreated and e-beam irradiated ACs X-ray photoelectronspectroscopy (XPS VGMultilab 2000ThermoVGScientificUK) analysis was performed using Al K120572 radiation XPS ele-mental analysis was used to determine the average elementalcontents in the sample The C1s peaks were deconvolutedinto several pseudo-Voigt functions (sums of a Gaussian-Lorentzian function) using a peak analysis program obtainedfrom Unipress Co USA The pseudo-Voigt function is givenby [17]

119865 (119864) = 119867[(1 minus 119878) exp(minus ln (2) (119864 minus 119864

0

119877FWHM)

2

)

+

119878

1 + ((119864 minus 1198640) 119877FWHM)

2]

(1)

where 119865(119864) is the intensity at energy 119864 119867 is the peakheight 119864

0is the peak center 119877FWHM is the full width at half-

maximum (FWHM) and 119878 is the shape function related tothe symmetry and the Gaussian-Lorentzianmixing ratioTheFWHM of the C1s peak was 13 eV

To characterize the crystalline structure of the ACsthe Raman spectra were recorded using a HORIBA Jobin-Yvon LabRam Aramis spectrometer (HORIBA Jobin-YvonEdison NJ) The 514 nm arrow of an Ar-ion laser was usedas the excitation source The G and D peak positions and the119868D119868G intensity ratio arewidely used for identifying the type ofcarbon and characterizing the carbon structureThe resultingRaman spectra were deconvoluted into G and D bands usingGaussian functions

The pore structures of the samples were assessed usingN2adsorption at 77K (ASAP2020 Micromeritics USA)The

specific surface areas of the samples were evaluated usingthe Brunauer-Emmett-Teller (BET) equation In addition thepore size distributions of the samples were determined usingdensity functional theory (DFT)

23 Electrochemical Characterization EDLC electrodes werefabricated by mixing 80wt AC 10wt carbon black(Super P Timcal Ltd Switzerland) and a 10wt solu-tion of polyvinylidene fluoride (PVDF Aldrich USA) inN-methyl pyrrolidone (NMP Aldrich USA) to form aslurry which was then painted onto a titanium plate TheAC-based electrodes were electrochemically characterizedusing a computer-controlled potentiostatgalvanostat (IviumTechnologies Netherlands) equipped with a three-electrodeassembly The AC-based electrode was used as the workingelectrode and Ag|AgCl was used as the reference electrodeA platinum plate was used as the counter electrode Cyclic

Inte

nsity

1000 800 600 400 200


Binding energy (eV)

Figure 1 XPS wide scan spectra of e-beam irradiated ACs

Table 1 XPS surface elemental analysis parameters of e-beamirradiated ACs

Sample Elemental contents (atomic percent) OC ()C O

R-AC 927 73 787E100-AC 934 66 707E200-AC 929 71 764E300-AC 933 67 718E500-AC 937 63 672

voltammetry (CV) of the electrode materials was performedover a potential range of 0 to 1 V at scan rates of 5 and50mV sminus1 in a 1M H

2SO4electrolyte

An AC impedance spectrum analyzer was employedto measure and analyze the impedance behavior of thecapacitors In this work themeasurements were conducted at0V with an AC potential amplitude of 5mV in the frequencyrange of 10mHz to 100 kHz

3 Results and Discussion

31 Changes in the Surface Chemical Properties of the E-Beam Irradiated Activated Carbons XPS elemental analysiswas conducted to compare the surface chemical propertiesof the ACs before and after e-beam irradiation As canbe observed in Table 1 and Figure 1 two main peaks areidentified marked C1s and O1s The peaks at approximately970ndash1 000 eV are the oxygenAuger peaks [18 19] As shown inTable 1 the samples are almost identical in terms of elementalcomposition The oxygen content of R-AC was found to beapproximately 73 at while the e-beam irradiated ACs hadoxygen contents of 63ndash71 atTherefore it is concluded thate-beam irradiation does not have a significant effect on thechemical composition of the AC surfaces




C(1)CndashC (sp2) 2845 641 732 746 703 663

C(2)CndashC (sp3) 2854 199 165 119 184 239

C(3)CndashO 2864 118 75 104 83 77

C(4)C=O 2874 42 28 31 30 21



119868D1119868G1 119868D2119868G2 119868G2119868G1

R-AC 186 116 248 236E200-AC 154 096 236 285E500-AC 175 124 185 251





119871119886= 44 times (

119868D1119868G1)

minus1

(2)





290 288 286 284 2820

1000

2000

3000

4000

5000

6000

Inte

nsity

Binding energy (eV)

C(1)

C(2)

C(3)C(4)

(a)

290 288 286 284 2820

1000

2000

3000

4000

5000

6000

Inte

nsity

Binding energy (eV)

C(1)

C(2)C(3)

C(4)

(b)

0

1000

2000

3000

4000

5000

6000

Inte

nsity


C(1)

C(2)C(3)

C(4)

(c)

290 288 286 284 2820

1000

2000

3000

4000

5000

6000In

tens

ity

Binding energy (eV)

C(1)

C(2)

C(3)C(4)

(d)

0

1000

2000

3000

4000

5000

6000

Inte

nsity


C(1)

C(2)

C(3)C(4)

(e)





2000 1800 1600 1400 1200 1000 800

Inte

nsity

(au

)

G2

G1 D1

D2


(a)

Inte

nsity

(au

)

G2

G1D1

D2


(b)

Inte

nsity

(au

)

G2

G1D1

D2


(c)






00 02 04 06 08 100

100

200

300

400

500

600

700

R-ACE100-AC

E200-AC

E300-ACE500-AC

Qua

ntity

adso

rbed

(cm

2g

STP

)



1 2 3 4 5000

005

010

015

020

025

R-ACE100-ACE200-AC

E300-ACE500-AC

Pore diameter (nm)

Volu

me (

cm3g

)











119862 =

1

119908Δ119881

int

1

0

119894 119889119905 (3)







00 02 04 06 08 10minus2

minus1

0

1

2Cu

rren

t (m

Am

g)



(a)


00 02 04 06 08 10

minus10

minus5

0

5

10

Curr

ent (

mA

mg)

(b)


0 4 8 12 16 20 240

4

8

12

16

20

24

R-ACE100-AC

E200-AC

E300-ACE500-AC

0 1 2 3 4 5 6012345

minusZ998400998400

(Ω)

Z998400(Ω)



4 Conclusions





Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






C(1)CndashC (sp2) 2845 641 732 746 703 663

C(2)CndashC (sp3) 2854 199 165 119 184 239

C(3)CndashO 2864 118 75 104 83 77

C(4)C=O 2874 42 28 31 30 21



119868D1119868G1 119868D2119868G2 119868G2119868G1

R-AC 186 116 248 236E200-AC 154 096 236 285E500-AC 175 124 185 251





119871119886= 44 times (

119868D1119868G1)

minus1

(2)





290 288 286 284 2820

1000

2000

3000

4000

5000

6000

Inte

nsity

Binding energy (eV)

C(1)

C(2)

C(3)C(4)

(a)

290 288 286 284 2820

1000

2000

3000

4000

5000

6000

Inte

nsity

Binding energy (eV)

C(1)

C(2)C(3)

C(4)

(b)

0

1000

2000

3000

4000

5000

6000

Inte

nsity


C(1)

C(2)C(3)

C(4)

(c)

290 288 286 284 2820

1000

2000

3000

4000

5000

6000In

tens

ity

Binding energy (eV)

C(1)

C(2)

C(3)C(4)

(d)

0

1000

2000

3000

4000

5000

6000

Inte

nsity


C(1)

C(2)

C(3)C(4)

(e)





2000 1800 1600 1400 1200 1000 800

Inte

nsity

(au

)

G2

G1 D1

D2


(a)

Inte

nsity

(au

)

G2

G1D1

D2


(b)

Inte

nsity

(au

)

G2

G1D1

D2


(c)






00 02 04 06 08 100

100

200

300

400

500

600

700

R-ACE100-AC

E200-AC

E300-ACE500-AC

Qua

ntity

adso

rbed

(cm

2g

STP

)



1 2 3 4 5000

005

010

015

020

025

R-ACE100-ACE200-AC

E300-ACE500-AC

Pore diameter (nm)

Volu

me (

cm3g

)











119862 =

1

119908Δ119881

int

1

0

119894 119889119905 (3)







00 02 04 06 08 10minus2

minus1

0

1

2Cu

rren

t (m

Am

g)



(a)


00 02 04 06 08 10

minus10

minus5

0

5

10

Curr

ent (

mA

mg)

(b)


0 4 8 12 16 20 240

4

8

12

16

20

24

R-ACE100-AC

E200-AC

E300-ACE500-AC

0 1 2 3 4 5 6012345

minusZ998400998400

(Ω)

Z998400(Ω)



4 Conclusions





Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




290 288 286 284 2820

1000

2000

3000

4000

5000

6000

Inte

nsity

Binding energy (eV)

C(1)

C(2)

C(3)C(4)

(a)

290 288 286 284 2820

1000

2000

3000

4000

5000

6000

Inte

nsity

Binding energy (eV)

C(1)

C(2)C(3)

C(4)

(b)

0

1000

2000

3000

4000

5000

6000

Inte

nsity


C(1)

C(2)C(3)

C(4)

(c)

290 288 286 284 2820

1000

2000

3000

4000

5000

6000In

tens

ity

Binding energy (eV)

C(1)

C(2)

C(3)C(4)

(d)

0

1000

2000

3000

4000

5000

6000

Inte

nsity


C(1)

C(2)

C(3)C(4)

(e)





2000 1800 1600 1400 1200 1000 800

Inte

nsity

(au

)

G2

G1 D1

D2


(a)

Inte

nsity

(au

)

G2

G1D1

D2


(b)

Inte

nsity

(au

)

G2

G1D1

D2


(c)






00 02 04 06 08 100

100

200

300

400

500

600

700

R-ACE100-AC

E200-AC

E300-ACE500-AC

Qua

ntity

adso

rbed

(cm

2g

STP

)



1 2 3 4 5000

005

010

015

020

025

R-ACE100-ACE200-AC

E300-ACE500-AC

Pore diameter (nm)

Volu

me (

cm3g

)











119862 =

1

119908Δ119881

int

1

0

119894 119889119905 (3)







00 02 04 06 08 10minus2

minus1

0

1

2Cu

rren

t (m

Am

g)



(a)


00 02 04 06 08 10

minus10

minus5

0

5

10

Curr

ent (

mA

mg)

(b)


0 4 8 12 16 20 240

4

8

12

16

20

24

R-ACE100-AC

E200-AC

E300-ACE500-AC

0 1 2 3 4 5 6012345

minusZ998400998400

(Ω)

Z998400(Ω)



4 Conclusions





Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






2000 1800 1600 1400 1200 1000 800

Inte

nsity

(au

)

G2

G1 D1

D2


(a)

Inte

nsity

(au

)

G2

G1D1

D2


(b)

Inte

nsity

(au

)

G2

G1D1

D2


(c)






00 02 04 06 08 100

100

200

300

400

500

600

700

R-ACE100-AC

E200-AC

E300-ACE500-AC

Qua

ntity

adso

rbed

(cm

2g

STP

)



1 2 3 4 5000

005

010

015

020

025

R-ACE100-ACE200-AC

E300-ACE500-AC

Pore diameter (nm)

Volu

me (

cm3g

)











119862 =

1

119908Δ119881

int

1

0

119894 119889119905 (3)







00 02 04 06 08 10minus2

minus1

0

1

2Cu

rren

t (m

Am

g)



(a)


00 02 04 06 08 10

minus10

minus5

0

5

10

Curr

ent (

mA

mg)

(b)


0 4 8 12 16 20 240

4

8

12

16

20

24

R-ACE100-AC

E200-AC

E300-ACE500-AC

0 1 2 3 4 5 6012345

minusZ998400998400

(Ω)

Z998400(Ω)



4 Conclusions





Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




00 02 04 06 08 100

100

200

300

400

500

600

700

R-ACE100-AC

E200-AC

E300-ACE500-AC

Qua

ntity

adso

rbed

(cm

2g

STP

)



1 2 3 4 5000

005

010

015

020

025

R-ACE100-ACE200-AC

E300-ACE500-AC

Pore diameter (nm)

Volu

me (

cm3g

)











119862 =

1

119908Δ119881

int

1

0

119894 119889119905 (3)







00 02 04 06 08 10minus2

minus1

0

1

2Cu

rren

t (m

Am

g)



(a)


00 02 04 06 08 10

minus10

minus5

0

5

10

Curr

ent (

mA

mg)

(b)


0 4 8 12 16 20 240

4

8

12

16

20

24

R-ACE100-AC

E200-AC

E300-ACE500-AC

0 1 2 3 4 5 6012345

minusZ998400998400

(Ω)

Z998400(Ω)



4 Conclusions





Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




00 02 04 06 08 10minus2

minus1

0

1

2Cu

rren

t (m

Am

g)



(a)


00 02 04 06 08 10

minus10

minus5

0

5

10

Curr

ent (

mA

mg)

(b)


0 4 8 12 16 20 240

4

8

12

16

20

24

R-ACE100-AC

E200-AC

E300-ACE500-AC

0 1 2 3 4 5 6012345

minusZ998400998400

(Ω)

Z998400(Ω)



4 Conclusions





Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Research Article Effects of E-Beam Irradiation on the...

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