Post on 25-Aug-2021
11NanoEngineering GroupNanoEngineering Group
Hydrogen StorageHydrogen Storage
Gang ChenGang ChenMassachusetts Institute of TechnologyMassachusetts Institute of Technology
Cambridge, MACambridge, MA
Collaborators :
Mildred S. Dresselhaus, MITVincent Berube, MITGregg Radtke, MITCostas Grigoropoulos, UCBSamuel Mao, UC BerkeleyXiao Dong Xiang, IntematixTaofang Zeng, NCSU
Sources :Thomas Audrey, PNNLJames Wang, SNLAndreas Zuttel, IfRES
Department of Energy
ENIC Tutorial
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OutlineOutline
Why hydrogen economy?Why hydrogen economy?
Hydrogen storage requirements/challengesHydrogen storage requirements/challenges
Ways to store hydrogenWays to store hydrogen
NanoscaleNanoscale effects on hydrogen storageeffects on hydrogen storage
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Energy Challenges: Climate ChangeEnergy Challenges: Climate Change
300
400
500
600
700
800
- 8
- 4
0
+ 4
400 300 200 100Thousands of years before present (Ky before present)
0
∆∆ ∆∆T relative to
present (
°C)
CH4(ppmv)
-------- CO2
-------- CH4
-------- ∆∆∆∆T
325
300
275
250
225
200
175
CO2(ppmv)
12001000 1400 1600 1800 2000
240
260
280
300
320
340
360
380
Year AD
Atm
ospheric CO2(ppm
v) Temperature
(°C)
- 1.5
- 1.0
- 0.5
0
0.5
1.0
1.5
-------- CO2
-------- Global Mean Temp
Relaxation times
50% of CO2 pulse to disappear: 50 - 200 years
transport of CO2 or heat to deep ocean: 100 - 200 years
Intergovernmental Panel on Climate Change, 2001http://www.ipcc.ch
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From Patrovic & Milliken (2003) and James WangSandia National Laboratories
StorageProduction Use
.
Distributed Generation
Transportation
ZERO/NEAR ZEROEMISSIONS
Biomass
HydroWindSolar
Coal
Nuclear
Natural Gas
Oil
With
Car
bon
Seq
uest
ratio
n
Storage isBottleneck
HIGH EFFICIENCY& RELIABILITY
.
Distributed Generation
Transportation
ZERO/NEAR ZEROEMISSIONS
Biomass
HydroWindSolar
Coal
Nuclear
Natural Gas
Oil
With
Car
bon
Seq
uest
ratio
n
Biomass
HydroWindSolar
Coal
Nuclear
Natural Gas
Oil
With
Car
bon
Seq
uest
ratio
n
Storage isBottleneck
HIGH EFFICIENCY& RELIABILITY
Hydrogen EconomyHydrogen Economy
Nuclear
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“ Tonight I'm proposing $1.2 billion in research fund ing so
that America can lead the world in developing clean ,
hydrogen-powered automobiles… With a new national
commitment, our scientists and engineers will overc ome
obstacles to taking these cars from laboratory to
showroom, so that the first car driven by a child b orn
today could be powered by hydrogen, and pollution-f ree.”
President Bush, State-of the-Union Address,
January 28, 2003
"America is addicted to oil, which is often importe d from
unstable parts of the world,“
“The best way to break this addiction is through
technology..”
“..better batteries for hybrid and electric cars, an d in
pollution-free cars that run on hydrogen’
President Bush, State-of the-Union Address,
January 31, 2006
Hydrogen: A National InitiativeHydrogen: A National Initiative
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Ways to Store HydrogenWays to Store Hydrogen
Compressed gasCompressed gas
Liquid hydrogenLiquid hydrogen
Condensed stateCondensed state
Volumetric densityVolumetric density
Gravimetric densityGravimetric density
KineticsKinetics
Heat transferHeat transfer
EfficiencyEfficiency
ReversibilityReversibility
Operation temperatureOperation temperature
Key Issues
77NanoEngineering GroupNanoEngineering Group
How large of a gas tank do How large of a gas tank do youyou want?want?
Schlapbach & Züttel, Nature, 15 Nov. 2001
Volume Comparisons for 4 kg Vehicular H 2 Storage
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DOE TargetsDOE Targets
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• Type IV all-composite tanks are available at 5000 p si (350 bar)
• 10,000 psi tanks being developed
Compressed Hydrogen GasCompressed Hydrogen Gas
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Liquid Hydrogen StorageLiquid Hydrogen Storage
From Patrovic & Milliken (2003)
dormancy
Linde Tank, GM
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Hydrogen Storage in Condensed StatesHydrogen Storage in Condensed States
PhysisorptionAdsorption on Surface
ChemisorptionAbsorption into Matter
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Potential ElementsPotential Elements
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Hydrogen Density of MaterialsHydrogen Density of Materials
T. Audrey
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J. E.Lennard-Jones, Trans. FaradaySoc. 28 (1932),pp. 333.
Potential energy for molecular and atomic hydrogen absorption
Desired binding energy range
500 0
AlH 3 MgH2 TiH2 LiH H-I H-SH H-CH3 H-OH
Carbon
physorption
Desirable rangeof binding energies:
10-60 kJ/mol(0.1 - 0.6 eV)
2H
PhysisorptionLow temperature
Molecular H2Bond strength [kJ/mol]
ChemisorptionHigh temperature
Atomic H
400300200100
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PhysisorptionPhysisorption
• Langmuir Isotherm
1
Kp
Kpθ =
+
Molecules Adsorbed
Number of Adsorption Siteθ =
1/ 2 expB
K Tk T
ε− ∝
Assumption: Monolayer coverage
0
0.2
0.4
0.6
0.8
1
0 2 104 4 104 6 104 8 104 1 105
θ
PRESSURE
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PhysisorptionPhysisorption
S. Brunauer, P. H. Emmett and E. Teller, J. Am. Chem. Soc., 1938, 60, 309 Multilayer coverage
BET Area
22,414m A
sp
V NA
σ=
Vm cm3/g at STP
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Research DirectionsResearch Directions
Increasing surface areaIncreasing surface area
Increasing binding energyIncreasing binding energy
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Increasing Surface AreaIncreasing Surface Area
Johnson, Chem. & Eng. News, 2002
MOF: Rosi et al., Science, 2003Roswell et al., JACS, 2004
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Increasing Binding EnergyIncreasing Binding Energy
http://www.wag.caltech.edu/fuelcells/index.html
Boron Doping of CNT,Z. Zhou et al., Carbon, 44, 939, 2006
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ChemisorptionChemisorption
A. Zuttel
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ClassificationClassification
Metal hydrides: MgHMetal hydrides: MgH22
Complex hydrides: NaAlHComplex hydrides: NaAlH44
Chemical hydrides: LiBH4, NHChemical hydrides: LiBH4, NH33BHBH33
MgH2 NaAlH4NH3BH3
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The Hydrogen BottleneckThe Hydrogen Bottleneck
From JoAnn Milliken (2002)
<100 <100 atmatm ..Operating Operating pressurepressure
(too high)(too high)--40 40 -- 60 60 °°°°°°°°CCOperating Operating
temperaturetemperature
(too slow)(too slow)30 s/kg30 s/kg --HH22Fueling time Fueling time
(reaction kinetics)(reaction kinetics)
$18/kWh$18/kWh$50/kWh$50/kWh$2/kWh$2/kWhSystem storage System storage costcost
LimitedLimited1500 cycles1500 cyclesReversibility Reversibility (cycle)(cycle)
81 kg/m81 kg/m 33Storage vol. %Storage vol. %
9%9%Storage wt. %Storage wt. %
Chemical Chemical hydridehydride
Metal Metal hydridehydride
DOE goal DOE goal (2015)(2015)
����
����
����������������
����������������
����������������
��������
���� ����
JoAnn Milliken (2002)
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PcTPcT RelationRelation
From A. Zuttel
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ThermodynamicsThermodynamics
A. Zuttel
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Stability of HydridesStability of Hydrides
A. ZuttelThermodynamic Equilibrium
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Energy BarrierEnergy Barrier
MHx
M+H2/2∆E
EnergyBarrier
Energy
Separation
Thermodynamically Favorable Does Not Mean Kinetical ly Favorable
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Reversible Metal Hydride SystemReversible Metal Hydride System
Sodium alanate doped with Ti is a reversible material hydrogen storage approach.
Low hydrogen capacity and slow kinetics are issues
NaAlH4
3NaAlH4 Na3AlH6 + 2Al + 3H2 3NaH + Al + 3/2H23.7 wt% 1.8 wt%
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System destabilization System destabilization
•Reduce energy (temperature) needed to liberate H2 by forming dehydrogenated alloy •System cycles between the hydrogen-containing state and the metal alloy instead of the pure metal•Reduced energy demand means lower temperature for hydrogen release.
Doping with a catalyst
•Reduces the activation energy.•Allows both exothermic and endothermic reactions to happen at lower temperature.
Forming new alloys
R.A. Zidan et al, J. Alloys and Compounds 285 (1999), pp. 119.
Mechanically Doped NaAlH 4
Gregory L. Olson DOE 2005 Hydrogen Program Annual Review
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A. Zuttel
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ImideImide (NH) and Amide (NH(NH) and Amide (NH 22))First step: LiNHFirst step: LiNH22 + + LiHLiH LiLi22NH + HNH + H22 (6.55% @ 300C,1atm.)(6.55% @ 300C,1atm.)
Li H LiNH
H
LiN H
Li
LiN
Li
Li
HH
HH
Second: LiSecond: Li22NH + NH + LiHLiH LiLi33N + HN + H22 (5% @ 300c 0.05atm)(5% @ 300c 0.05atm)
�� Release temperature too high and low release pressure.Release temperature too high and low release pressure.
LiN H
LiLi H
Partial Mg substitution reduces release temperature
Li 1-xMgxNH2
S. Orimo et al., Appl. Phys. A:Materials Science & Processing, Vol 79, No 7, p. 1765 - 1767.
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Chemical HydridesChemical Hydrides
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Irreversible Chemical HydridesIrreversible Chemical Hydrides
20 - 35% sol.Stabilized with
1-3% NaOH
Borax in NaOHCatalyst
NaBH4 + 2H2O →→→→ NaBO2 + 4H2
2LiH + 2H2O →→→→ 2LiOH + 2H2
Light mineral oil slurry, proprietary stabilizers
Pastebyproduct
2Na + 2H2O →→→→ 2NaOH + H2
Polyethylene-coated pellets, mechanically cut to expose Na
• Hydrogen capacity is high at around 10 wt% hydrogen .• Dehydrogenation kinetics are fast.• Reactions are irreversible on-board vehicle.
Regeneration costs are a major issue
From Patrovic & Milliken (2003)
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Fueling CycleFueling Cycle
From DOE BES Hydrogen Report
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NN--EthylcarbazoleEthylcarbazole (Air Products, Inc.)(Air Products, Inc.)
T. Audrey
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(kg m-3)
110120
Metal ammine complexesMetal ammine complexes
Mg(NHMg(NH33))66ClCl22 = MgCl= MgCl22 + 6NH+ 6NH33 (9.1%) @ T <620K(9.1%) @ T <620K
Ammonia is toxicAmmonia is toxic
Can be used in high T solid oxide fuel cells.Can be used in high T solid oxide fuel cells.
High temperature of hydrogen releaseHigh temperature of hydrogen release
2NH2NH33 3H 3H22+ N+ N22 @ ~600K@ ~600K
Christensen et al., J. Mater. Chem., 2005, 15, 4106–4108
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•• HyridingHyriding reaction: reaction: ~1 MW for 5 min. ~1 MW for 5 min.
•• NanostructuredNanostructuredmaterials impair heat materials impair heat transfertransfer
•• Temperature rise Temperature rise suppresses suppresses hydridinghydridingreactionreaction
•• Typical hydride Typical hydride conductivity: k~0.1 conductivity: k~0.1 W/mW/m--KK
Conductive foams, fins and meshes
Expanded Graphite Compacts
Klein et. al., Int. J. Hydrogen Energy 29 (2003) 1503-1511
See: Zhang et. al., J. Heat Transfer, 127 (2005) 1391-1399
Foams: Al, C, etc.Foams: Al, C, etc.
Wire meshWire mesh
SOLUTIONS
Thermal ManagementThermal Management
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Benefits of NanostructuresBenefits of Nanostructures
Increase kinetics: diffusion time ~ radius square/diffusivityIncrease kinetics: diffusion time ~ radius square/diffusivity
Possibility of coPossibility of co--existence of existence of chemichemi-- and and physiphysi--sorptionsorption
Possibility of changing thermodynamic propertiesPossibility of changing thermodynamic properties
• Yang’s Equation:
MHxMHx
2i op p
r
σ− = Surface Tension
Radius
pi
po
• Kelvin Theory:� For multiphase system, transition
temperature, equilibrium pressure and enthalpy of reaction change with radius.
� For hydride, we can expect similar dependence in release temperature, equilibrium pressure and enthalpy of formation.
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Simultaneous Simultaneous PhysisorptionPhysisorption and and ChemisorptionChemisorption
0 5 10 15 200.0
0.5
1.0
1.5
2.0
2.5
3.0
hydr
ogen
upt
ake
(wt.%
)
pressure (bar)
MgNi:SiO2 sorption
MgNi:SiO2 desorption
MgNi:SiO2 sorption (7 days)
MgNi:SiO2 desorption (7 days)
SiO2 sorption
SiO2 desorption
target material
laser pulse expanding
metal vapor
nanoporous sample
S.Mao, LBNL
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Size Effects on Thermodynamic PropertiesSize Effects on Thermodynamic Properties
Assuming the following reactionAssuming the following reaction
M + HM + H22 MHMH22 2
ln( )MHo
M H
aG G RT
a P∆ = ∆ +
2ln eq o o
H
H SP
RT R
∆ ∆= −
2
( ) ( ) ln( )
3 ( , )
MHo
M H
M M MH
aG r G r RT
a P
V r
r
γ→
∆ = ∆ +
∆+
2/ 3
( , ) ( ( ) ( ))MHM MH MH M adsoption
M
Vr r r E
Vγ γ γ→
∆ = − +
Bulk molar free energy of formation
Nanoparticle molar free energy of formation
At At nanoscalenanoscale, surface and size , surface and size affect reaction enthalpy.affect reaction enthalpy.�� Increase the surface to Increase the surface to
volume ratio.volume ratio.�� Increase adsorption sites due Increase adsorption sites due
to low coordination surface to low coordination surface atoms.atoms.
�� Lower binding energy in Lower binding energy in small metallic clusters.small metallic clusters.
Van’t Hoff relation
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Modeling DFT ResultsModeling DFT Results
If internal energy dependence on If internal energy dependence on radius is all contained in the radius is all contained in the surface energy termsurface energy term
3 ( , )( ) M M MH
Bulk
V rE r E
r
γ→∆∆ ≈ ∆ +
Following Following Tolman’sTolman’s work, surface work, surface tension is allowed to vary with tension is allowed to vary with radiusradius
1
o
a
r
∆∆ =+ DFT values of internal energy DFT values of internal energy
calculated by calculated by WagemansWagemans et al. et al. J.AmJ.Am. Chem. Soc. 2005, 127. Chem. Soc. 2005, 127
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• Nanoparticles with positive ∆∆∆∆ will have
Enthalpy of ReactionEnthalpy of Reaction
2
3ln eq o M M MH o
H
H V SP
RT rRT R→∆ ∆ ∆= + −
3 M M MHeff o
VH H
r→∆∆ = ∆ +
Lower equilibrium temperatureLess heat release during hydrogenation
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Improving Improving sorptionssorptions properties with nanotechnologyproperties with nanotechnology
The bulk hydride sorption rate is prohibitively sma ll and releasThe bulk hydride sorption rate is prohibitively sma ll and releas e temperature is e temperature is too high.too high.Reducing grain and particle size increases kinetics and uptake.Reducing grain and particle size increases kinetics and uptake.Surface energies and material properties at nanosca le offer ways to tune the energetics of absorption and desorption.
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NanoscafoldingNanoscafolding to improve kinetics and change to improve kinetics and change thermodynamics: thermodynamics: BorazaneBorazane (NH(NH33BHBH33))
Scaffolding decreases H wtScaffolding decreases H wt--% % by half.by half.
Reversibility is still an issueReversibility is still an issue
T. T. AutreyAutrey et al., et al., AngewAngew. Chem. Int. Ed. 2005, 44, 3578 . Chem. Int. Ed. 2005, 44, 3578 ––3582.3582.
NanoscaffoldingNanoscaffolding improves improves kinetics and reduces enthalpy kinetics and reduces enthalpy of formation (catalytic effect)of formation (catalytic effect)
Reduces Reduces emmissionsemmissions of of unwanted chemicalsunwanted chemicals
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Mass and Heat TransferMass and Heat Transfer
αααα ββββ
Hydriding/dehydridingReaction
H2 mass diffusion
Nanoscaleheat transfer
Nanostructuredmaterial
• The strongly exothermic hydridingreaction increases the sample’s temperature which reduces the reaction rate or even stops the reaction altogether.
• Rapid hydriding reaction thus requires effective heat removal solution.
• Nanostructures usually have poor heat transfer characteristics. Therefore, we need to balance mass diffusion kinetics with heat transfer.
• Diffusion limited hydride reaction.
• Optimal pore and particle sizes: balance pore diffusion and diffusion in the solid particle to control kinetics.
100
101
102
103
80 120 160 200 240 280
KX,BULK (FOURIER LAW)
KZ,BULK (FOURIER LAW)
KZ,FILM, EXPERIMENTAL
KX,FILM, EXPERIMENTALT
HE
RM
AL
CO
ND
UC
TIV
ITY
(W
/mK
)
TEMPERATURE (K)
Si0.5Ge0.5
BULK ALLOY (300K)
Lines--Fitting with Chen’s Model
P=0.6
P=0.5
P=0.6
Cross-Plane
In-Plane
100
101
102
103
80 120 160 200 240 280
KX,BULK (FOURIER LAW)
KZ,BULK (FOURIER LAW)
KZ,FILM, EXPERIMENTAL
KX,FILM, EXPERIMENTAL
100
101
102
103
80 120 160 200 240 280
KX,BULK (FOURIER LAW)
KZ,BULK (FOURIER LAW)
KZ,FILM, EXPERIMENTAL
KX,FILM, EXPERIMENTALT
HE
RM
AL
CO
ND
UC
TIV
ITY
(W
/mK
)T
HE
RM
AL
CO
ND
UC
TIV
ITY
(W
/mK
)
TEMPERATURE (K)
Si0.5Ge0.5
BULK ALLOY (300K)
Lines--Fitting with Chen’s Model
P=0.6
P=0.5
P=0.6
Cross-Plane
In-Plane
100
101
102
103
80 120 160 200 240 280
KX,BULK (FOURIER LAW)
KZ,BULK (FOURIER LAW)
KZ,FILM, EXPERIMENTAL
KX,FILM, EXPERIMENTAL
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SummarySummary
Key issues: Key issues: volumetric and gravimetric density.volumetric and gravimetric density.
Thermodynamics: Thermodynamics: sorption/sorption/desorptiondesorption temperature.temperature.
Kinetics, mass and heat transfer: Kinetics, mass and heat transfer: pumping timepumping time
Reversibility: Reversibility: cycling timecycling time
NanoscaleNanoscale effects on storage density, effects on storage density, thermodynamics, kinetics, and heat transferthermodynamics, kinetics, and heat transfer