Metal hydride formation and hydrogen storage in al li alloys iri symposium may 22 2003
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Metal hydride formation and hydrogen storage in Al-Li alloys IRI Symposium May 22, 2003. A. Rivera Defects in Materials, IRI, TUDelft Work supported by the Delft Institute for Sustainable Energy (DISE) Contributors at DM:

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Metal hydride formation and hydrogen storage in al li alloys iri symposium may 22 2003

Metal hydride formation and hydrogen storage in Al-Li alloysIRI SymposiumMay 22, 2003

A. Rivera

Defects in Materials, IRI, TUDelft

Work supported by the Delft Institute for Sustainable Energy (DISE)

Contributors at DM:

A. van Veen (head), F. Labohm, J. de Roode, W.J. Legerstee, K.T. Westerduin, S.W.H. Eijt, H. Schut.

External contributors (Materials Science Faculty, TUDelft):

R. Delhez, N. van der Pers


World energy consumption

World energy consumption

To reduce oil dependency  Hydrogen


How to store hydrogen

A 1000 kg car consumes

5-6 kg fuel/100 km

The same car would consume

2 kg H2/100 km in combustion mode or

1 kg H2 /100 km in fuel cell mode

However, at room temperature and atmospheric pressure 1 kg H2 occupies 11 m3

Storage:

Pressurised vessels

Liquified H2

Sorbed at surface or bulk materials

How to store hydrogen?


Contents

Contents

  • Material requirements

    • Examples

  • Non-transition light metal hydrides

  • Experimental developments

  • Al-Li materials

  • Conclusions and further work


Material requirements

Material requirements

  • Storage capacity > 5 wt. %

  • Fast reaction kinetics

  • H2 release: 100 kPa at T < 200 ºC

  • Reversibility in the range 0 – 200 ºC

  • Resistance to degradation

  • Cost

  • Safety


Sources of inefficiencies

Hysteresis between absorption and desorption

Hydride stability

Limited kinetics

Poor heat conduction

Small diffusion constant

Surface reactions

Necessity for initial hydriding activation

Sensitivity to air, impurities or other gases

Volume expansion

Decrepitation into fine powder

Sources of inefficiencies


Storage and release

Hydrogen in solution: α-phase

Hydrogen in hydride: β-phase

Formation of hydride: α & β

M + ½xH2 MHx + ΔQ

Isotherm flat

More plateaux can appear

Storage and release

  • Desorption isotherm is lower due to stress

  • This is undesired for hydrogen storage

  • Formation enthalpy can be obtained


Kinetics

E.g. MgH2 at 600 K

Slow diffusion

Kinetics

1 μm / s


Hydrogen storage materials

Hydrogen storage materials


Key properties

Key properties


Non transition light metal hydrides

LiAlH4, NaAlH4 (in water  irreversible full H2 release)

High capacities (10 and 5 wt.%, respectively)

No reversible due to decomposition

3 LiAlH4Li3AlH6 + 2 Al + 3 H2[150-175 oC]

Li3AlH6 + 2 Al 3 LiH + 3 Al + 1.5 H2[180-220 oC]

3 LiH + 3 Al  3 AlLi + 1.5 H2[387-425 oC]

Slow kinetics

Catalysts, as Fe, Ti and Zr

Make some steps reversible

Improve the kinetics

Non-transition light metal hydrides


Our approach

Our approach

  • Objective: to develop nanostructured light weight alloys for hydrogen storage

  • Choice:Al-Li compounds

  • Preparation

    • Sputtering of Al-Li alloy or LiAlH4

    • Laser ablation of Al-Li alloy or LiAlH4

    • Cathodic charge, ion implantation gas or plasma exposure + annealing

  • Characterisation

    • Volumetric analyses, Permeation, TDS, XRD, NDP, PBA

    • Occasionally ERDA, SEM, TEM


Gas analysis techniques

Gas analysis techniques

  • Hydra

    • Hydrogen absorption and desorption experiments

    • Desorption detection limits 1013 - 1022 H2 molecules

    • Dynamic measurements give direct information on kinetics

    • Appropriate for thin films

  • Permeation

    • of solved molecules or electrochemically introduced atoms

    • in situ after sputtering will become available soon

  • Sensitive thermal desorption spectrometry

    • Detection limit as low as 1011 H2 molecules

    • Significantly lower for D2


Hydra

Hydra


Hydra1

Hydra

Expansion

volume

M1

10-2-10 Pa

M2

10-105 Pa

M0

0.1-6 MPa

Mix volume

Gas inlet

To pumps

Pd filter

Mass analyser

Cell (90-900 K)


Hydra static

Hydra (static)

M1

1015-1017 H2

M2

1017-1022 H2

Expansion

volume

M0

0.1-6 MPa

Mix volume

Gas inlet

To pumps

Pd filter

Mass analyser

Cell (90-900 K)


Hydra dynamic

Hydra (dynamic)

Expansion

volume

M1

M2

M0

0.1-6 MPa

Mix volume

Gas inlet

To pumps

Pd filter

Mass analyser

1012-1015 H2/s

1013-1016 H2

Cell (90-900 K)


Hydra software

Hydra software


Desorption of lialh 4

Desorption of LiAlH4

  • 0.4 mg LiAlH4, 0.1 K/s

  • Total H2: 1.5x1022 g-1

  • Total gas: 3.9x1022 g-1

  • 0: Hydroxide

  • 1: LiAlH4

  • 2: Li3AlH6

  • 3: LiH


Metal hydride formation and hydrogen storage in al li alloys iri symposium may 22 2003

Sputter deposited Al-Li: SEM

  • SEM evidences the formation of columnar structures in the nm range, size increases with distance from substrate

~1 µm sputter deposited Pd layer

Pd

~1 µm sputter deposited Al-Li at room temperature, the layer contains 5at.%Li (NDP)

Al Li


Sputter deposited al li hydrogen

Sputter deposited Al-Li: Hydrogen

  • Dynamic measurements:

    • High sensitivity

    • Easy background estimation

    • Peaks indicate kinetics processes

  • Around 0.5 at.H%

  • Recharging results in low T peak of 0.3 at.H%


Conclusions and further work

Conclusions and further work

  • Effort to fulfil material requirements

  • Successful H2 detection techniques

  • Successful creation of samples by

    • Sputtering

    • Laser ablation

  • Currently:

    • High Li content samples from LiAlH4 targets

    • Study of samples with high porosity

    • Fundamental study of Li nanocrystals in c-Al


Further information

Further information

  • Contact

    • A. Rivera: [email protected]

    • A. van Veen: [email protected]


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