An efficient mechanochemical synthesis of alpha-aluminum hydride: Synergistic effect of TiF₃ on the crystallization rate and selective formation of alpha-aluminum hydride polymorph

α-AlH₃ is one of the most promising hydrogen storage materials due to its high gravimetric hydrogen capacity and low dehydriding temperature. In present work, a convenient and cost-efficient solid-state mechanochemical reaction is proposed to obtain α-AlH₃ nano-composite. With the addition of TiF₃, α-AlH₃ nano-composite was formed in a short period by milling of LiH and AlCl₃. Based on XRD and NMR results, the average grain size of the α-AlH₃ in the nano-composite was 45 nm. The reaction pathway as well as the synergistic effect of TiF₃ on the solid state reaction between LiH and AlCl₃ were confirmed. In the α-AlH₃/LiCl nano-composite, TiF₃ reduced the temperature of dehydriding reaction and improved dehydrogenation rate of α-AlH₃. Within the temperature range between 80 and 160 °C, dehydrogenation of the as-milled α-AlH₃ nano-composite showed fast kinetics. At 160 °C, a maximum hydrogen desorption of 9.92 wt% was obtained within 750 s, very close to the theoretical hydrogen capacity of α-AlH₃.