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 °C, which is 80 °C lower than the onset dehydrogenation temperature of commercial LiAlH4. About 6.3 wt.% H2 can be released isothermally at 100 °C (800 min) or at 120 °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 LiAlH4·4THF, which is obtained by ball milling the dehydrogenated products of TiH2nano-doped LiAlH4 in the presence of THF and 5 MPa H2. This suggests that TiH2 is also an effective catalyst for the formation of LiAlH4·4THF.

► Nano-sized TiH2 prepared by reactive milling is proved for the first time to be an excellent catalyst for LiAlH4. ► Dehydrogenation temperature of LiAlH4 decreased to 75 °C with 6.3 wt.% H2 released. ► Activation energies for the first two dehydrogenations were reduced by 20 and 24 kJ mol−1. ► Regeneration of LiAlH4 was realized in the presence of TiH2 and THF.