Enhanced dehydrogenation properties of LiAlH₄-Mg₂NiH₄ nanocomposites via doping Ti-based catalysts

Metal alanate and magnesium-based hydride complex has potential to promote the application of hydrogen storage materials in energy storage systems. In this work, the hydrogen storage properties of LiAlH₄-Mg₂NiH₄ destabilized system with Ti-based additives were investigated. Both the dehydrogenation temperature and kinetics of LiAlH₄-Mg₂NiH₄ were significantly improved by doping TiF₃, surpassing those of the Ti- and TiO₂-doped LiAlH₄-Mg₂NiH₄ composites. Particularly, the onset dehydrogenation temperature of the TiF₃ doped LiAlH₄-Mg₂NiH₄ composite was reduced to as low as 50 °C, far superior to that of the undoped sample and the Ti- and TiO₂-doped samples. The hydrogen desorption activation energy of TiF₃-doped LiAlH₄-Mg₂NiH₄ composite was 81.56 kJ mol^-1 fitted by Johnson-Mehl-Avrami model, which was lower than that of the undoped composite (85.30 kJ mol^-1). The XPS results indicated that Al₃Ti (Ti⁰) phase could be in situ formed during dehydrogenation process, exerting positive catalytic effect on the dehydrogenation of the TiF₃-doped LiAlH₄-Mg₂NiH₄ composite. Moreover, the TiF₃-doped LiAlH₄-Mg₂NiH₄ composite also exhibited desirable re-hydrogenation behavior.