Enhanced dehydrogenation properties of LiBH4 compositing with hydrogenated magnesium-rare earth compounds

LiBH4 is regarded as a promising hydrogen storage material due to its high hydrogen density. In this study, the dehydrogenation properties of LiBH4 were remarkably enhanced by doping hydrogenated Mg3RE compounds (RE denotes La, Ce, Nd rare earth metals), which are composed of nanostructured MgH2 and REH2+x (denoted as H − Mg3RE). For the LiBH4 + H − Mg3La mixture, the component LiBH4 desorbed 6 wt.% hydrogen even at a relatively low temperature of 340 °C, far lower than the desorption temperature of pure LiBH4 or the 2LiBH4 + MgH2 system. This kinetic improvement is attributed to the hydrogen exchange mechanism between the H − Mg3La and LiBH4, in the sense that the decomposition of MgH2 and LaH2+x catalyzed the dehydrogenation of LiBH4 through hydrogen exchange effect rather than mutual chemical reaction requiring higher temperature and hydrogen pressure. However, prior to fast hydrogen release, the hydrogen exchange effect suppressed the dehydriding of MgH2 and elevated its desorption temperature. It is expected to strengthen the hydrogen exchange effect by compositing the LiBH4 with other nanosized metal hydrides and to obtain better dehydrogenation properties.

► Hydrogenated magnesium-rare earth compounds improved the dehydrogenation of LiBH4. ► A hydrogen exchange effect existed between MgH2 and LiBH4 in the dehydrogenation. ► Hydrogen exchange promoted the decomposition of LiBH4 at 340 °C. ► Hydrogen exchange increased the desorption temperature of MgH2.