Significantly improved hydrogen storage properties of Mg90Al10 catalyzed by TiF3

Magnesium hydride (MgH ₂ ) is one of the most promising materials for solid state hydrogen storage, but overly stable thermodynamics and sluggish kinetics of hydrogenation and dehydrogenation hinders its application. In this study, Mg ₉₀Al ₁₀ was prepared by hydriding combustion synthesis (HCS), and then various Ti-based compounds (Ti, TiH ₂, TiO ₂ and TiF ₃) were introduced into Mg ₉₀Al ₁₀ by ball milling. Mg ₉₀Al ₁₀ + 10 wt% TiF ₃ displays the most excellent dehydrogenation property compared with those doped with other Ti-based compounds. For instance, due to the addition of 10 wt% TiF ₃ , the peak dehydrogenation temperature and the apparent dehydrogenation activation energy of the composite are 86 °C and 77.1 kJ/mol lower than those of Mg ₉₀Al ₁₀ (364 °C and 155.95 kJ/mol). In addition, the catalytic effect of TiF ₃ on the hydrogen storage properties of Mg ₉₀Al ₁₀ has been investigated in detail. Except for the unreacted TiF ₃, Al ₃Ti and MgF ₂ can be found during the first dehydrogenation process and remain stable in the subsequent de/hydrogenation cycles, which can act as the active sites to accelerate the hydrogen dissociation and recombination. Therefore, the excellent hydrogen storage properties of Mg ₉₀Al ₁₀ + 10 wt% TiF ₃ can be attributed to the catalytic effect of TiF ₃, in-situ formed Al ₃Ti and MgF ₂ . Our result is very significant to emphasize the practical application of the Mg-Al hydrogen storage alloys.