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Altering Hydrogen Storage Properties by Hydride Destabilization through Alloy Formation: LiH and MgH_2 Destabilized with Si

Vajo, John J. and Mertens, Florian and Ahn, Channing C. and Bowman, Robert C., Jr. and Fultz, Brent (2004) Altering Hydrogen Storage Properties by Hydride Destabilization through Alloy Formation: LiH and MgH_2 Destabilized with Si. Journal of Physical Chemistry B, 108 (37). pp. 13977-13983. ISSN 1520-6106. doi:10.1021/jp040060h.

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Alloying with Si is shown to destabilize the strongly bound hydrides LiH and MgH_2. For the LiH/Si system, a Li_(2.35)Si alloy forms upon dehydrogenation, causing the equilibrium hydrogen pressure at 490 °C to increase from approximately 5 × 10^(-5) to 1 bar. For the MgH_2/Si system, Mg_2_Si forms upon dehydrogenation, causing the equilibrium pressure at 300 °C to increase from 1.8 to >7.5 bar. Thermodynamic calculations indicate equilibrium pressures of 1 bar at approximately 20 °C and 100 bar at approximately 150 °C. These conditions indicate that the MgH2/Si system, which has a hydrogen capacity of 5.0 wt %, could be practical for hydrogen storage at reduced temperatures. The LiH/Si system is reversible and can be cycled without degradation. Absorption/desorption isotherms, obtained at 400−500 °C, exhibited two distinct flat plateaus with little hysteresis. The plateaus correspond to formation and decomposition of various Li silicides. The MgH2/Si system was not readily reversible. Hydrogenation of Mg2Si appears to be kinetically limited because of the relatively low temperature, <150 °C, required for hydrogenation at 100 bar. These two alloy systems show how hydride destabilization through alloy formation upon dehydrogenation can be used to design and control equilibrium pressures of strongly bound hydrides.

Item Type:Article
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URLURL TypeDescription
Vajo, John J.0000-0002-6271-4899
Bowman, Robert C., Jr.0000-0002-2114-1713
Fultz, Brent0000-0002-6364-8782
Additional Information:© 2004 American Chemical Society. Received 26 January 2004. Published online 19 August 2004. Published in print 1 September 2004. C.C.A. would like to acknowledge partial support for this work by DOE through Energy Efficiency and Renewable Energy Grant No. DE-FC36-01GO11090 and by the Chemical and Environmental Sciences Laboratory of General Motors Research and Development Center. This research was partially performed at the Jet Propulsion Laboratory, which is operated by the California Institute of Technology under contract with the U.S. National Aeronautics and Space Administration (NASA).
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Department of Energy (DOE)DE-FC36-01GO11090
General Motors Research and Development CenterUNSPECIFIED
Issue or Number:37
Record Number:CaltechAUTHORS:20170524-113943677
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Official Citation:Altering Hydrogen Storage Properties by Hydride Destabilization through Alloy Formation:  LiH and MgH2 Destabilized with Si John J. Vajo, Florian Mertens, Channing C. Ahn, Robert C. Bowman, Jr., and Brent Fultz The Journal of Physical Chemistry B 2004 108 (37), 13977-13983 DOI: 10.1021/jp040060h
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:77711
Deposited By: Ruth Sustaita
Deposited On:24 May 2017 21:19
Last Modified:15 Nov 2021 17:33

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