Improved reversible hydrogen storage of LiAlH4 by nano-sized TiH2

Transition metal halides are mostly used as dopants to improve the hydrogen storage properties of LiAlH4, but they will cause hydrogen capacity loss because of their relatively high molecular weights and reactions with LiAlH4. To overcome these drawbacks, active nano-sized TiH2 (TiH2nano) prepared by reactive ball milling is used to dope LiAlH4. It shows superior catalytic effect on the dehydrogenation of LiAlH4 compared to commercial TiH2. TiH2nano-doped LiAlH4 starts to release hydrogen at 75 degrees C, which is 80 degrees C lower than the onset dehydrogenation temperature of commercial LiAlH4. About 6.3 wt.% H-2 can be released isothermally at 100 degrees C (800 min) or at 120 degrees C (150 min). The apparent activation energies of the first two dehydrogenation reactions of LiAlH4 are reduced by about 20 and 24 kJ mol(-1), respectively. Meanwhile, the regeneration of LiAlH4 is realized through extracting the solvent from LiAlH4 center dot 4THF, which is obtained by ball milling the dehydrogenated products of TiH2nano-doped LiAlH4 in the presence of THF and 5 MPa H-2. This suggests that TiH2 is also an effective catalyst for the formation of LiAlH4 center dot 4THF. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.