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Hydrogen Sorption Behavior of the ScH_2−LiBH_4 System: Experimental Assesment of Chemical Destabilization Effects

Purewal, Justin and Hwang, Son-Jong and Bowman, Robert C., Jr. and Rönnebro, Ewa and Fultz, Brent and Ahn, Channing (2008) Hydrogen Sorption Behavior of the ScH_2−LiBH_4 System: Experimental Assesment of Chemical Destabilization Effects. Journal of Physical Chemistry C, 112 (22). pp. 8481-8485. ISSN 1932-7447. doi:10.1021/jp800486n.

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The hydrogen storage reaction ScH_2 + 2LiBH_4 → ScB_2 + 2LiH + 4H_2 (8.91 wt %), based on the thermodynamic destabilization of LiBH_4, is predicted to have a reaction enthalpy of ΔH_(300K) = 34.1 kJ/mol H_2. The isothermal kinetic desorption behavior in this system was measured. At temperatures up to 450 °C, less than 5 wt % H_2 is released, which is only half of the theoretical capacity. Powder X-ray diffraction data indicate that LiBH_4 has decomposed into LiH in the final desorption product, but the data provide no evidence that ScH_2 has participated in the reaction. Magic angle spinning NMR (MAS NMR) results do not show that the expected ScB_2 equilibrium product phase has formed during desorption. While the addition of 2 mol % TiCl_3 catalyst does improve desorption kinetics at 280 °C, it does not otherwise assist the destabilization reaction. The calculated reaction enthalpy suggests that this system should be of interest at moderate temperatures, but the large heats of formation of the reactant phases in this system appear to play a critical role in determining overall kinetics. Furthermore, the formation of a Li_2B_(12)H_(12) intermediate phase was determined by MAS NMR, which is an undesirable stable product if reaction reversibility is to be accomplished.

Item Type:Article
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URLURL TypeDescription
Hwang, Son-Jong0000-0002-3210-466X
Bowman, Robert C., Jr.0000-0002-2114-1713
Fultz, Brent0000-0002-6364-8782
Additional Information:© 2008 American Chemical Society. Received: January 17, 2008; Revised Manuscript Received: February 27, 2008. The authors thank J. W. Reiter (J.P.L.), P. R. Wilson (J.P.L.), H. Kabbour (Caltech), L. Miura (Caltech), and C. Kim (Caltech) for their contributions to these studies. We acknowledge discussions with Hui Wu and T. Udovic. This work was partially supported by the DOE through Award Nos. DE-AI-01-05EE11105 and DE-FC36-05GO15065. This research was partially performed at the Jet Propulsion Laboratory, which is operated by the California Institute of Technology under contract with NASA. The NMR facility at Caltech was supported by the National Science Foundation (NSF) under Grant No. 9724240 and partially supported by the MRSEC Program of the NSF under Award No. DMR-0520565.
Funding AgencyGrant Number
Department of Energy (DOE)DE-AI-01-05EE11105
Department of Energy (DOE)DE-FC36-05GO15065
Issue or Number:22
Record Number:CaltechAUTHORS:20170426-140106425
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Official Citation:Hydrogen Sorption Behavior of the ScH2−LiBH4 System: Experimental Assesment of Chemical Destabilization Effects Justin Purewal, Son-Jong Hwang, Robert C. Bowman, Jr., Ewa Rönnebro, Brent Fultz, and Channing Ahn The Journal of Physical Chemistry C 2008 112 (22), 8481-8485 DOI: 10.1021/jp800486n
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:76956
Deposited By: Tony Diaz
Deposited On:26 Apr 2017 21:14
Last Modified:15 Nov 2021 17:04

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