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Catalyzed Nano-Framework Stabilized High Density Reversible Hydrogen
Storage Systems
E. RönnebroT. Boyle
Sandia National Laboratories
F.-J. WuJ. StricklerAlbemarle
Corporation
S. Arsenault, D. Mosher, S. Opalka, X. Tang, T. Vanderspurt, B. Laube, R. BrownUnited Technologies Research Center
DOE Hydrogen Program Annual Merit Review
Arlington, VAJune 9, 2008
Project ID STP16
This presentation does not contain any proprietary, confidential, or otherwise restricted information
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Overview
Timeline7/1/07 Start (signed 9/4/07)7/1/10 End
Budget$1.26M Total Program DOE: $1.01M
SNL: $360kAlbemarle: $90kCost share: 20% (31% UTRC $)
FY07: $80kFY08: $480k
Barriers AddressedP. Lack of Understanding of Hydrogen Physisorption and ChemisorptionA. System Weight and VolumeE. Charging/Discharging Rates
www.eere.energy.gov/hydrogenandfuelcells/mypp
Partner ParticipationSandia National LaboratoriesAlbemarle CorporationAspen Aerogels
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ObjectivesDesign & synthesize hydride / nano-framework combinations to improve:
Reversible capacity Desorption temperature Cyclic life
Build upon successes previously demonstrated in the community and extend to a wider range of doped, functionalized and catalyzed framework chemistries to:Advance the understanding of behavior modification by nano-frameworks Obtain / maintain nano-scale phase domainsTune hydride / framework interactions to
Decrease desorption temperature for highly stable compoundsStabilize high capacity compounds – ligand eliminationInfluence desorption product formation
Activate H2 dissociation on highly dispersed catalytic sites
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High Level Approach
Framework Synthesis
Hydride Synthesis
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5
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Hea
t Flo
w (W
/g)
0 100 200 300 400T em perature (°C )
2007-091D SC .03 LiBH 4 0 .5gr Spex m il led 15m in2007-091D SC .07 Silica 0.25gr L iBH 4 0 .25gr
E xo U p U niversa l V 4.4A TA Ins
Screening CharacterizationChemical reactivities: DSC, TGAFramework morphology: BET
Hydride Incorporation
Structure & PerformanceSEM, TEM, Sievert’s
Atomistic & Thermodynamic ModelingFramework design, Material compatibility
Down-select
HSCVASP
DSCReaction Testing
0 100 200 300 400 5000.00
0.05
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0.15
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C
kmol
Temperature
H2(g)
ZrO2 BLiBH4
Li2ZrO3ZrH2
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0 1 2 3 4 5Time (Hours)
Pres
sure
(bar
)
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400
Tem
pera
ture
(°C
)
LiBH4 + SiO2 (aerogel) Desorption, 290°C, 1bar
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Detailed ApproachPhase
TaskPhase I
Years 1 & 2Phase IIYear 3
First Principles Modeling
Examine hydride / framework interactions.Screen doped / catalyzed / functionalized frameworks.
Evaluate mechanisms of down-selected hydride / framework systems.
Thermodynamic Modeling
Assess chemical compatibility of hydride / framework combinations.
Comparison of bulk scale & nano scale properties.
Hydride Development
Synthesize high capacity hydride materials.
Refine high capacity hydride synthesis methods.
Hydride Incorporation
into NFS
Incorporate hydrides into designed frameworks.Characterize properties.
Maximize hydride incorporation into framework for improved capacity.
Nano-Framework
Development
Synthesize and characterize uncatalyzed and catalyzed frameworks.
Optimize doped / catalyzed / functionalized framework for down-selected systems.
Iterative design and synthesis of high H2 capacity systems.
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Milestones
Date Milestone or Go / No Go Decision
2008 Q1 Select advanced nano-framework structure
2008 Q1 Demonstrate synthesis of desired nano-framework structure
2008 Q2 Synthesize top UTRC / Albemarle candidate hydride material
2008 Q4 Evaluate relative performance of catalysts
2008 Q4 Synthesize optimal catalyzed nano-framework structure
2009 Q1 Demonstrate loading of UTRC / Albemarle hydride into catalyzed framework
2009 Q2 Demonstrate loading of Sandia hydride into catalyzed framework
2009 Q3Go / No Go on whether to proceed with original plan or redirect based on:> 50% hydride deposition into the CFSReasonable absorption/desorption behavior for at least one cyclePerformance relative to the state-of-the-art material shows promise
2008 Q1 Synthesize top Sandia candidate hydride material
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Material Focus & Partner Roles
A&TM: Atomistic and Thermodynamic ModelingNFS: Nano Framework Structure
HSM
HSMCSMNFS
CSM
NFS
A&TM
Hydrogen Storage Material (HSM)SNL: Ca(BH4)2 (stable borohydride)UTRC / Albemarle: NaTi(BH4)4*ligand, …Compatibility screening / Baseline modeling: LiBH4
HSM: Hydrogen Storage MaterialCSM: Combined Structure & Material
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Capabilities – Nano-Framework Development
Autoclave System2200 PSI 300°C
Wet Chemistry Laboratory
Process DevelopmentRange of chemistries– Oxides– Non-oxides– Polymers, …
Large Scale Manufacturing– Future cost reduction
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Capabilities – Hydride Synthesis / Incorporation
Autoclave System- Solvated incorporation- 2200 PSI- 300°C
Solid State Processing- Very rapid, low cost
screening- Limited conditions- High cost for high
volume production
Solution Based ProcessingChemical Design & Synthesis- Excellent control- High purity products- Expensive processing- Cost- effective high
volume production
High-Pressure station- Solid state reactions- Wide range of P and T <20,000psi, <500°C- Autoclave with six samples capability
Solvated Hydride Incorporation- Solvents selected for ease of
removal
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Experimental Methods – Characterization
XRD of SBP LiMg(AlH4)3
Monoclinic structurerefinement from PND and SR-PXD ongoingInstitute for Energy, NO.
Inte
nsity
2θ (degrees)
XRD of SBP LiMg(AlH4)3
Monoclinic structurerefinement from PND and SR-PXD ongoingInstitute for Energy, NO.
Inte
nsity
2θ (degrees)
Crystalline structure & phase
X-Ray DiffractionDifferential Scanning Calorimetry
Assess reversibility potential, phase behavior
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0 100 200 300Temperature (°C)
Hea
t Flo
w (W
/g)
168.2°C
140.3°C
192.6°C
132.3 J/g10.5 J/gExo
Endo 158.0 J/g
Thermogravimetry-Mass Spectroscopy
Desorption temperature & species
0.E+00
1.E-09
2.E-09
3.E-09
4.E-09
5.E-09
0 100 200 300 400 500 600Temperature(˚C)
Ion
coun
t /m
g H2
NH3
( )No co-reactant
0.E+00
1.E-09
2.E-09
3.E-09
4.E-09
5.E-09
0 100 200 300 400 500 600Temperature(˚C)
Ion
coun
t /m
g H2
NH3
( )No co-reactant
* Additional characterization support will be provided by other MHCoE partners
Morphology, catalyst dispersion and size, hydride loading
TEM / High Res SEM
Quantify total metal loading
Inductively CoupledPlasma
BET Nitrogen Porosimetry
Surface area, average pore size, and pore size distribution
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Hydride
~5 nm diameter
Pore
Concept Input Models RoleAtomic Modeling of Hydride-NFS Interactions
Al2O3NFSWallSlab
LiBH4HydrideCluster
NFS wall~ 0.6 nm
thick
Interface
Mechanistic simulations guide NFS down-selection, design and modification.
Hydride thermodynamics
Interfacial physi-/chemisorptionreactions influence on hydride stability and dehydrogenation
NFS stability and modification:a) Doping to tune reactivity b) Loading with H2 activation
catalysts for reversibilityc) Surface functionalization
SchematicFilled NFS
Density Functional TheoryGround State Minimization
Direct Method Lattice DynamicsThermodynamic Property Prediction
Conduct atomic modeling toinvestigate and prescreen:
Baseline System
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Adhesion to NFSΔHadh (kJ/mole LiBH4)
(- =favorable)-37 -35 -18
Screening of NFS Stability and Hydride Interactions
ZrO2 NFS predicted to have low reducibility in an H2 atmosphere and weaker tunable interfacial associative interactions with LiBH4.
(strong binding weak binding)
Strategy:Guide experiments by determining promising as well as unfavorable system characteristics.
Baseline System:LiBH4 is highly stable.Balance reversibility by increasing dehydrogenation product interactionwith NFS.
LiBH4 LiBH4 LiBH4
Al2O3SiO2 ZrO2
LiBH4 on Al2O3 LiBH4 on ZrO2LiBH4 on SiO2
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Hydride Physi-/Chemisorption Interactions w/ NFS
• Dehydrogenation influenced by product adsorption on NFS surface. • Ca(BH4)2/NFS under investigation.
Fully Charged DischargedGround State Dehydrogenation Reaction Predictions
ΔHdeh
kJ/mole LiBH4
8LiBH4 w/o NFS 8 LiH + 8B + 12H2 +1148LiBH4 / Al2O3
Al2O3∗2Li∗2H + 6LiH+8B +12H2 +1008LiBH4 / ZrO2
ZrO2∗Li+ 7LiH + 8B + 12.5H2 +112Equally strong Li-Obond in charged and
discharged states
LiBH4 on Al2O3
Adsorbed Li & H enhance discharge
LiBH4 on ZrO2
2Li & 2H on Al2O3
∗ = AdsorbedExperimental thermodynamic ΔHdeh at 298 K:100 kJ/(mole LiBH4), HSC v. 5.1.104 kJ/(mole LiBH4), Smith and Bass,
J. Chem. Eng. Data 8 (1963) 8.
Li on ZrO2
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NFS Doping Alters Hydride DehydrogenationLiBH4 on
Sc-doped ZrO2
LiBH4 onTi-doped ZrO2
LiBH4 onV-doped ZrO2
Ground State LiBH4Dehydrogenation Reaction Predictions on NFS
ΔHdeh
kJ/mole LiBH4
Zr0.92Ti0.08O2 +125
ZrO2 +112Zr0.92Sc0.08O2 +85
Zr0.92V0.08O2 +120
NFS dopants used to balance both lattice stability and electronic NFS/hydride interfacial interactions. Sc predicted to enhance LiBH4 dehydrogenation.
Dopants substituted in most favorable position. Increased hydride interactions with increased typical formal dopant valence.
Calculated for favorable discharge to single adsorbed *Li on surface.
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Thermodynamic Modeling - NFS / Hydride Compatibility
Objective: Use thermodynamic modeling in combination with experimentation to guide design of stable framework compositions.
Predicted reaction from thermodynamics motivates additional modeling and experimental efforts.
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F
C
Temperature
H2(g)
ZrO2 B
LiBH4Li2ZrO3
ZrH2
Km
ol
Examined additional compositions to determine NFS stability and system reversibility with borohydrides:
5 Oxides3 Carbides1 Nitrides
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Thermodynamic Modeling – Potential Oxide Reduction
Only LiBH4 thermodynamic data initially available in HSC SoftwareOxides may be susceptible to reductionSiO2 was reported as catalyst for LiBH4 dehydrogenation1, but has shown thermodynamic instability
Currently conducting thermodynamic evaluations of Ca(BH4)2 / NFS interactions
Methods to prevent oxide reduction and examine the possibility of boronic acid formation are being explored.
4LiBH4 + 3SiO2 = 2Li2O*SiO2 + Si + 4B + 8H2(g)ΔG298K = -49.286 kJ
Example: Possible hydride reactivity with NFS
1. A. Züttel, S. Rentsch, P. Fischer, P. Wenger, P. Sudan, Ph. Mauron, Ch. Emmenegger, “Hydrogen Storage Properties of LiBH4”, J. Alloys and Compounds 356 (2003)
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XerogelInitial focus on oxide and carbon materials:
Xerogels (SiO2, Al2O3, ZrO2): 5nm & >300m2/g
Cryogels (Al2O3): 5 - 20nm & >300m2/g
SiO2 Aerogels: 17nm & > 550m2/g
Carbon Aerogel: 10 - 25nm & >600m2/g
Nano-Framework Materials Development
Cryogel
SiO2Aerogel
CarbonAerogel
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Hydride DevelopmentMetal borohydrides, Alkaline (Ak)-Transition metal (Tm)-B-H, were developed under contract DE-FC36-04GO14012.Multistep reactions significantly lower dehydrogenation onset temperatures and improved kinetics. Only trace B2H6/B3H9detected in the outgas.
400ºC
2E-10
2.5E-10
3E-10
3.5E-10
4E-10
4.5E-10
5E-10
0 100 200 300 400 500 600Temperature (˚C)
H2
ion
Cur
rent
/mg
of A
kBH
4
Ak-Tm-B-H-1
AkBH4
Ak-Tm-B-H-2
Ak-Tm-B-H-4
TGA/MS
For compounds with limited reversibility, the NFS will inhibit irreversible segregation thus improving reversibility.
H2 Desorption
0.0%
4.0%
8.0%
12.0%
0 1 2 3 4 5 6Time (hour)
H2
wt%
Ak-Tm-B-H-2b, 400˚C
Ak-Tm-B-H-4, ˚
Ak-Tm-B-H-1, 500˚C
Ak-Tm-B-H-6, 400˚C
H2 Desorption
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NaTi(BH4)4∗ligand – Up to 7.3 wt% H2 Endothermic
Down-selected NaTi(BH4)4 based on potential for reversibility, low desorption temperature and possible solution based incorporation.
Wavenumbers (cm-1)
Starting complex
Starting complex (fully charged)
60ºC Discharge, 20ºC Recharge100ºC Discharge
B-H peak range (1900 – 2500 cm-1)
*
*
*Starting complex (fully charged)
60ºC Discharge, 20ºC Recharge100ºC Discharge
B-H peak range (1900 – 2500 cm-1)
*
*
*
Abs
orba
nce
Diffuse Reflectance Infrared Fourier Transform Spectra
Starting complex (fully charged)60ºC Discharged, 20ºC recharged100ºC Discharged
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11B MAS NMR and XRD show re-formation of Ca(BH4)2 after re-hydriding at 330°C and 100 bar
Bowman, Hwang,
Kim, Reiter, ZanRönnebro
Ca(BH4)2
Ca(BH4)2 as made
Desorbed at 450°C
Desorption at 320°C
Re-hydrided at 330°C
ppm
+H2 CaB6
a-B
* * likely B12H12
Hydride Material – Ca(BH4)2
See more details on Ca(BH4)2 in ST36, Ronnebro, Majzoub
CaB6 + 2CaH2 + 10 H2 → 3Ca(BH4)2 @700bar, 400°C, 48hours
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Sc
B
N
H
C
Solvated Synthesis of Metal Borohydridessolv
MXn = ScCl3, TiCl4, ZrBr4,CaI2;; solv = THF, DME or MeOH
MXn + n NaBH4 M(BH4)n(solv)x
THF
Solution deposition of MBH onto silica substrate illustrates that deposition by this method will be possible. However, contamination with NaX by product appears to be
problematic. Schemes to further purify the MBH from the NaX are underway.
Ca
BOH
C
Ca(BH4)2(DME)2Sc(BH4)3(py)3
CaI2 +2NaBH4 Ca(BH4)2(solv)xsolv
• single crystal X-ray diffraction confirms Ca(BH4)2(DME)2 was synthesized. Used for deposition studies, with THF adduct
looking the most promising
DME
MeOH
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AlBr3 + 3 NaBH4 Al(BH4)3 + 3 NaBr
2 Al(BH3)3 + 3 Ca(NR2)2 3 Ca(BH4)2 + 2 Al(NR2)3
2 Al(BH3)3 + 3 MgR2 3 Mg(BH4)2 + 2 AlR3
tol
tol
tol
Zanella et al. Inorganic Chemistry 2007 (ASAP).
Solvent-free Synthesis of Metal Borohydrides
Identification of final materials not consistent with known PXRD patterns of Mg(BH4)2or Ca(BH4)2. Contamination by Br indicates additional work to purify final product
necessary. Sequential stepwise characterization of intermediates underway.
AlBr3 + 3 LiBH4 + 2/3 Ca(NR2)2 in tol/reflux
20 25 30 352-Theta(°)
x10^3
5.0
10.0
15.0
Inte
nsity
(Cou
nts)
[MgBH4.xy]
2 Al(BH3)3 + 3 MgR2 in tol
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Hydride / Framework Compatibility Screening
Compatibility screening ⇒ DSC
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Rev
Hea
t Flo
w (W
/g)
0 100 200 300 400 500Temperature (°C)
2008-014DSC.003 LiBH4_ZrO2 50-502008-014DSC.001 LiBH4
Exo Up Universal V4.5A TA Ins
ZrO2 + LiBH4
LiBH4
LiBH4
Xerogel
Ball Mill
Press Pellet Melt LiBH4(290°C, 190Bar)
LiBH4 use for initial compatibility screening because of high reactivity, availability, and existing thermodynamic data.
DSC screening to determine reaction compatability of framework with hydride.
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Compatibility Screening – SiO2 + LiBH4
Possible non-reversibility suggested via thermodynamic assessment. DSC shows split peak at 280-300°C suggesting reaction event.
Potential Reaction Pathway4LiBH4 + 3SiO2 → 2Li2O*SiO2 + 4B + Si + 8H2(g)
ΔG298K = - 49.286 KJ
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t Flo
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0 50 100 150 200 250 300 350 400 450Temperature (°C)
2008-045DSC.002 Silica sol-gel (Xerogel)+LiBH42008-045DSC.007 LiBH4
Exo Up Universal V4.5A TA In
Hea
t Flo
w (W
/g)
Temperature (C)
SiO2 + LiBH4
LiBH4
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Compatibility Screening – SiO2 + LiBH4
After discharge LiBH4 is decomposed but unidentified peaks exist.Conclusion: SiO2 is reactive with hydride and unsuitable for NFS.
10 15 20 25 30 35 40 450
500
1000
1500
50 55 60 65 70 75 80 85Two-Theta (deg)
0
500
1000
1500
[ ] g g y pp97-000-0853> Li 2SiO 3 - Lithium Catena-silicate
97-001-5414> Li 2(Si 2O5) - Dilithium Phyllo-disilicate97-006-1753> LiD - Lithium Deuteride
97-009-0849> Li 4(B4Si8O24) - Tetralithium Tetraborooctasilicate
Inte
nsity
(Cou
nts)
theta cal
Bkd, Ka2, DSeal Subtd
XRD data after 290°C, 1 bar, 6 hours
No LiBH4 (RT, HT)Unidentified Peaks
Li2SiO3Li2(Si2O5)LiHLi4(B4Si8O24)
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Compatibility Screening – ZrO2 + LiBH4
DSC of ZrO2 + LiBH4 is similar to LiBH4, suggesting that ZrO2 is stable and non-reactive in the presence of this strongly reducing hydride.
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2H
eat F
low
(W/g
)
0 100 200 300 400 500 600Temperature (°C)
2008-045DSC.007 LiBH42008-045DSC.005 Zirconia (HS) (Xerogel)+LiBH4
Exo Up Universal V4.5A TA In
Hea
t Flo
w (W
/g)
Temperature (C)
ZrO2 + LiBH4
LiBH4
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Solution coating of ceramic (SiO2 initially) substrate with metal borohydride.
Solvent selection is critical:Stability in synthesis and depositionBinding to surface is appropriate
Analyze air-sensitive materials.
base
O-ring
Berylliumdome
Specimenplate assemblyVacuum port
(sealed)
Specimenplate
BeD-XRD
Solvated Hydride Incorporation
Volatile enough to be removed prior to BH4 decomposition
Solution Deposition
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Project Summary
ModelingSimulations show interfacial NFS interactions can alter stability of hydride and discharged products.Dopants balance both NFS lattice stability and electronic NFS/hydride interfacial interactions.
Framework and HydrideInitial nano-framework structures have been synthesized (ZrO2, Al2O3, SiO2, TiO2, Carbon).Multiple suitable oxide candidates have been identified. ZrO2 selected because of low reducibility.Compatibility screening reactions with LiBH4 have been performed.UTRC / Albemarle focus on ligand stabilized: NaTi(BH4)4∗ligand Sandia focus on stable borohydride: Ca(BH4)2
Improve reversibility of high capacity hydride candidates by developing advanced NFS chemistries through combined modeling and experimentation.
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Atomistic ModelingSimulate Ca(BH4)2 and NaTi(BH4)4∗ligand hydride interactions with ZrO2 NFS. Virtually tune doped NFS to balance hydride stability and dehydrogenation. Virtually develop doped, functionalized, catalyzed NFS to enhance reversibility.
Framework and HydrideEvaluate initial oxide (ZrO2) aerogel.Continue to assess oxide, modified carbon and other alternative framework materials. Examine support interactions with selected NaTi(BH4)4∗ligand and Ca(BH4)2.Evaluate doped, heterogeneously catalyzed and functionalized nano-frameworks.
Future Plans
Ca(BH4)2 on ZrO2