AlH3 is a metastable hydride with a theoretical hydrogen capacity of 10.01 wt % and is very easy to decompose during ball milling especially in the presence of many catalysts, which will lead to the attenuation of the available hydrogen capacity. In this work, AlH3 was ball milled in air (called "air-milling") with layered Ti3C2 to prepare a Ti3C2-catalyzed AlH3 hydrogen storage material. Such air-milled and Ti3C2-catalyzed AlH3 possesses excellent hydrogen storage performances, with a low initial decomposition temperature of just 61 °C and a high hydrogen release capacity of 8.1 wt %. In addition, 6.9 wt % of hydrogen can be released within 20 min at constantly 100 °C, with a low activation energy as low as 40 kJ mol-1. Air-milling will lead to the formation of an Al2O3 oxide layer on the AlH3 particles, which will prevent continuous decomposition of AlH3 when milling with active layered Ti3C2. The layered Ti3C2 will grip on and intrude into the AlH3 particle oxide layers and then catalyze the decomposition of AlH3 during heating. The strategy employing air-milling as a synthesis method and utilizing layered Ti3C2 as a catalyst in this work can solve the key issue of severe decomposition during ball milling with catalysts economically and conveniently and thus achieve both high-capacity and low-temperature hydrogen storage of AlH3. This air-milling method is also effective for other active catalysts toward both reducing the decomposition temperature and increasing the available hydrogen capacity of AlH3.
Keywords: AlH3; Ti3C2; catalysis; hydrogen storage; stabilization.