Claus Hviid ChristensenClaus Hviid Christensen
Novel Indirect Hydrogen Storage MaterialsNovel Indirect Hydrogen Storage Materials
www.csg.dtu.dkwww.csg.dtu.dk
March 23, 2004APS March MeetingMontreal, Canada
Presented by:Mildred Dresselhaus
Massachusetts Institute of [email protected]
617-253-6864
Basic Research Needs Basic Research Needs for the Hydrogen Economyfor the Hydrogen Economy
Hydrogen Hydrogen StorageStorage for for VehiclesVehicles
3.59 wt% 1.37 wt%Schlapbach & Züttel, Nature
Direct Hydrogen StorageDirect Hydrogen Storage• Liquefied H2
– Boil-off, cost of liquefying, safety• High pressure H2
– Cost of compression, safety, volumetric density• Metal hydrides, e.g. MgH2
– Low bulk density, kinetics• Complex hydrides, e.g. NaAlH4, LiAlH4
– kinetics/catalyst, synthesis, reversibility• Chemical hydrides, e.g. borane-ammonia adducts
– Expensive materials, reversibility, complex system• Physisorption in porous materials
– Material developments, synthesis, gravimetric and volumetric density
Indirect Hydrogen StorageIndirect Hydrogen Storage• Methane
– reforming, reformate clean-up, volumetric density
• Methanol– reforming, reformate clean-up, safety
• Ethanol– reforming, reformate clean-up, cost
• Ammonia– reforming, safety
Ammonia as Hydrogen CarrierAmmonia as Hydrogen Carrier
• Dense liquid; ∼ 18wt% of hydrogen• Optimized catalyst exist• Relatively easy to reform to H2
• But liq. NH3 is normally considered too dangerous !!??
Ammonia Storage in AmminesAmmonia Storage in Ammines
300 400 500 6000
2x10-5
4x10-5
6x10-5
8x10-5
1x10-4
0
1
2
3
4
5
6
Accu
mul
ated
NH
3 cap
acity
[mol
NH
3 / m
ol M
gCl 2]
NH
3 des
orpt
ion
rate
[mol
/s]
Temperature [Κ]
2nd run
Desorption temperature ramp: 10 K/min
1st run
Mg(NH3)6Cl2 (s) → MgCl2 (s)+ 6NH3(g)
4 : 1 : 1
Christensen et al., J. Mater. Chem. 15 (2005) 4105.
New Concept for Energy Storage:New Concept for Energy Storage:using Metal Ammine Complexesusing Metal Ammine Complexes
Hydrogen
Nitrogen
Integrated ammoniadecomposition catalyst
Release(thermal desorption)
Storage unit
NH3: “largest” chemical in the world
MgCl2
Stored as NH3
Mg(NH3)6Cl2
To fuel cell
Ammonia Decomposition is CentralAmmonia Decomposition is Central
Boisen, Dahl, Nørskov, Christensen, J. Catal. 230 (2005) 318.
2NH3
⇅N2 + 3H2
(nm)
NHNH33 Release from Compact Tablets:Release from Compact Tablets:SelfSelf--generated generated NanoporosityNanoporosity
Sym
met
ry a
xis
R=R0
HeatAmminesalt unit
Porousfront
NH3
2-4nm 15-40nm
Sørensen, Johannessen, Nørskov and Christensen, Catal. Today 111 (2006) 140.
Energy Level DiagramEnergy Level Diagram
Hummelshøj, Sørensen, Kustova, Johannessen, Nørskov and Christensen, J. Am. Chem. Soc. 128 (2006) 16.
Indirect Solid Storage Indirect Solid Storage –– Mg(NHMg(NH33))66ClCl22
E_desorp E_migr. E_H-vac
Mg(NH3)Cl2 ~ 0.5 eV <0.6 eV ~ 0.5 eV
Hummelshøj, Christensen, Honkala, Nørskov, unpublished
DOE 2005DOE 2010
DOE 2015
Details on the Hydrogen CapacityDetails on the Hydrogen Capacity
0 5 10 15 200
20
40
60
80
100
120
140
NH3(l)
Ca(NH3)8Cl2
volu
met
ric H
2 den
sity
[kg
H2 p
r m-3]
gravimetric H2 density [mass %]
liquid H2
Mg(NH3)
6Cl
2 Measured capacity.Not theoretical value
“Virtual” H2-pressure:∼1300 bar!
22ndnd Generation PrototypeGeneration Prototype–– Integrated NHIntegrated NH33 DecompositionDecomposition
Insulate the decomposition reactor with the storage material…
Compact HCompact H22--Producing SystemProducing SystemH2 + N2
H2 + N2
Mg(NH3)6Cl2-cartridge
IntegratedNH3-decomp. reactor
Traces of NH3: Absorption in degassed salt (< 10ppm NH3)
μ-reactor for production of H2:Sørensen, Nielsen, Jensen, Hansen, Johannessen, Quaade, Christensen, Catal. Comm., 6 (2005) 229
SummarySummaryOn-going work
• Heat management– NH3-decomposition
reactor• Purification
– for PEM-FC• Packaging/recycling
Current status• High demonstrated density
– 9.1 wt% H2; 108 kg H2/m3
• Reversible• Fast release kinetics• Simple to handle in open
atmosphere• Inexpensive (ca. 0.5 €/kg)• CO2-free energy carrier