Mechanical and Thermal Dehydrogenation of Lithium Alanate (LiAlH4) and Lithium Amide (LiNH2) Hydride Composites

Crystals

Robert A. Varin¹ 

[1] Department of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Ave. W., N2L 3G1, Waterloo, Ontario, Canada

关键词: solid state hydrogen storage;    lithium alanate;    lithium amide;    ball milling;    mechanical and thermal dehydrogenation;   

DOI  :  10.3390/cryst2020159

来源: mdpi

【 摘 要 】

Hydrogen storage properties of the (nLiAlH₄ + LiNH₂) hydride composite where n = 1, 3, 11.5 and 30, synthesized by high energy ball milling have been investigated. The composite with the molar ratio n = 1 releases large quantities of H₂ (up to ~5 wt.%) during ball milling up to 100–150 min. The quantity of released H₂ rapidly decreases for the molar ratio n = 3 and is not observed for n = 11.5 and 30. The XRD studies indicate that the H₂ release is a result of a solid state decomposition of LiAlH₄ into (1/3)Li₃AlH₆ + (2/3)Al + H₂ and subsequently decomposition of (1/3)Li₃AlH₆ into LiH + (1/3)Al + 0.5H₂. Apparently, LiAlH₄ is profoundly destabilized during ball milling by the presence of a large quantity of LiNH₂ (37.7 wt.%) in the n = 1 composite. The rate of dehydrogenation at 100–170 °C (at 1 bar H₂) is adversely affected by insufficient microstructural refinement, as observed for the n = 1 composite, which was milled for only 2 min to avoid H₂ discharge during milling. XRD studies show that isothermal dehydrogenation of (nLiAlH₄ + LiNH₂) occurs by the same LiAlH₄ decomposition reactions as those found during ball milling. The ball milled n = 1 composite stored under Ar at 80 °C slowly discharges large quantities of H₂ approaching 3.5 wt.% after 8 days of storage.

【 授权许可】

CC BY   
© 2012 by the authors; licensee MDPI, Basel, Switzerland.