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

Abstract

AlH 3 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-AlH 3 nano-composite. With the addition of TiF 3 , α-AlH 3 nano-composite was formed in a short period by milling of LiH and AlCl 3. Based on XRD and NMR results, the average grain size of the α-AlH 3 in the nano-composite was 45 nm. The reaction pathway as well as the synergistic effect of TiF 3 on the solid state reaction between LiH and AlCl 3 were confirmed. In the α-AlH 3 /LiCl nano-composite, TiF 3 reduced the temperature of dehydriding reaction and improved dehydrogenation rate of α-AlH 3. Within the temperature range between 80 and 160°C, dehydrogenation of the as-milled α-AlH 3 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-AlH 3 .

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