Improved hydrogen storage property of Li-Mg-B-H system by milling with titanium trifluoride

The Li-Mg-B-H system that is prepared from 2LiH + MgB2 or 2LiBH(4) + MgH2 possesses high hydrogen capacity and relatively favorable thermodynamics, but it is greatly restricted in practical hydrogen storage applications by problematic H-exchange kinetics. In the present study, TiF3 was mechanically milled with a 2LiH + MgB2 mixture and examined with respect to its effect on reversible dehydrogenation of the Li-Mg-B-H system. Experimental study showed that TiF3 is highly effective for promoting the two-step dehydrogenation reaction in the Li-Mg-B-H system. Compared to the neat 2LiH + MgB2 sample, the 2LiH + MgB2 + 0.01TiF(3) sample exhibits significantly reduced dehydrogenation temperature and markedly enhanced dehydriding rate at both steps. Furthermore, the catalytic enhancement arising upon adding TiF3 additive was observed to persist well in the hydrogenation/dehydrogenation cycles. Based on the results of phase analysis and a series of designed experiments, the mechanism underlying the observed property improvement is discussed.