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

Abstract

The Li–Mg–B–H system that is prepared from 2LiH + MgB₂ or 2LiBH₄ + 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 + 0.01TiF₃ 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.