Magnesium borohydride: A new hydrogen storage material

摘要

Magnesium borohydride (Mg(BH_4)_2) is a promising material for hydrogen storage because of its high gravimetric storage density (15.0mass%). We intended to synthesize Mg(BH_4)_2 by decomposition reaction of LiBH_4 with MgCl_2 by heat treatment without using a solvent, where the product consists of LiCl and a compound of magnesium, boron and hydrogen. Hydrogen desorption temperature of the product is approximately 100 K lower than that of LiBH_4 and the decomposition consists of a two-step reaction. The products of the 1st and 2nd decomposition reactions are MgH_2 and Mg, respectively. This result indicates the following two-step reaction (lst reaction: Mg(BH_4)_2→MgH_2 + 2B + 3H_2, 2nd reaction: MgH_2→Mg + H_2). The first decomposition peak is dominant and is around 563 K. The 2nd decomposition occurs at the temperature greater than 590 K.