Study on the dehydrogenation properties and reversibility of Mg(BH4)2AlH3 composite under moderate conditions

Mg(BH 4 ) 2 has been considered as one of the promising light metal complex hydrides due to its high hydrogen capacity and low cost. But its higher thermal stability (dehydrogenation at above 300 °C) needs to be improved for the practical application. In this study, the aluminum hydride AlH 3 was introduced into complex borohydride Mg(BH 4 ) 2 to synthesize a new Mg(BH 4 ) 2 AlH 3 composite by ball milling method. It is found that the active Al ∗ formed from the self-decomposition of AlH 3 can effectively improve the dehydrogenation properties of Mg(BH 4 ) 2 , the Mg(BH 4 ) 2 AlH 3 composite starts to release hydrogen at 130.8 °C with a total hydrogen capacity of 11.9 wt.%. The dehydrogenated products of the composite is composed of Mg 2 Al 3 and B at 350 °C, resulting in the improved hydrogen desorption properties of Mg(BH 4 ) 2 AlH 3 composite. The Mg 2 Al 3 and B products would be further transformed into MgAlB 4 and Al at 500 °C. Moreover, the Mg 2 Al 3 and B dehydrogenated products show better reversible hydrogen storage property than that of the MgAlB 4 and Al products. This research shows a way to alter hydrogen de/hydrogenation route and reversibility of Mg(BH 4 ) 2 complex hydride by compositing with AlH 3 and controlling the dehydrogenation temperature.