Hydrogen storage in Mg-LiBH sub(4) composites catalyzed by FeF sub(3)

Mg-10 mol% LiBH sub(4) composite plus small amounts of FeF sub(3) is investigated in the present work. The presence of LiBH sub(4) during the milling process noticeably modifies the size and morphology of the Mg agglomerates, leading to faster hydrogenation and reaching almost the theoretical hydrogen capacity owing to enhanced hydrogen diffusion mechanism. However, the dehydrogenation of the system at low temperatures ([< or =]300 [degrees]C) is still slow. Thus, FeF sub(3) addition is proposed to improve the dehydrogenation kinetic behavior. From experimental results, it is found that the presence of FeF sub(3) results in an additional size reduction of the Mg agglomerates between ~10 and -100 mu m and the formation of stable phases such as MgF sub(2), LiF and FeB. The FeB species might have a catalytic effect upon the MgH sub(2) decomposition. As a further result of the FeF sub(3) addition, the Mg-10 mol%LiBH sub(4)-5 mol% FeF sub(3) material shows improved dehydrogenation properties: reduced dehydrogenation activation energy, faster hydrogen desorption rate and reversible hydrogen capacities of about 5 wt% at 275 [degrees]C.