Synthesis and hydrogen storage characteristics of Mg-B-H compounds by a gas-solid reaction

摘要

Magnesium borohydride [Mg(BH_4)_2] is an attractive complex hydride for hydrogen storage. In this study, attempts to synthesize Mg(BH_4)_2 were carried out by a solid-gas reaction through MgH_2 and B_2H_6 in the absence of a liquid medium. The source of B_2H_6 was obtained by heating a mixture of NaBH_4 and ZnCl_2. The profile of pressure versus temperature indicated that the absorption kinetics of B_2H_6 by MgH_2 were slow. Structural analysis confirmed the formation of Mg-B-H compounds. The reaction products presented two-step hydrogen release during heating. A small amount of hydrogen could be released from the as-synthesized Mg-B-H compounds at a low temperature of 215 ℃. The slow reaction kinetics were significantly affected by the surface conditions of the MgH_2 powders.