TiF₃ and Ti(OBu-n)₄-doped MgH₂ and Mg₂NiH₄ were investigated with regard to hydrogen desorption performance. It was found that the onset temperature for hydrogen release was around 420 ℃ for the blank MgH₂, but decrease to 360 and 410 ℃ for the TiF₃- and the Ti(OBu-n)₄-doped MgH₂, respectively. For Mg₂NiH₄, it was reduced from 230 to 220 ℃ after doping with TiF₃, but remained unchanged once doping with Ti(OBu-n)₄. These indicate that TiF₃ is more efficient than Ti(OBu-n)₄ in reducing the stability of MgH₂ and Mg₂NiH₄. The enhanced desorption kinetics is attained in the TiF₃-doped MgH₂, but not in the TiF₃-doped Mg₂NiH₄. Combined with XRD and FTIR techniques, the catalytic activity was thought to be jointly influenced by the crystal structure of the hydride and the electronic structure of the catalyst. The decrease in hydrogen release temperature and the improvement in kinetics are owing to the weakening of the Mg(Ni)—H bonds through the interactions between the catalyst and the hydride, thus facilitating energetically the formation of intra-H…H pairings that further recombine readily towards the molecular hydrogen.

Key words: Ti doping, hydrogen desorption, MgH₂, Mg₂NiH₄