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 Technologymillie@mgm.mit.edu

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

The HThe H22 PathwayPathwayReversible!

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

Safe Hydrogen Storage!Safe Hydrogen Storage!1.5 liter H2 and a lighter…

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

Thank you for your attentionThank you for your attention