Synthesis of Mg-based composite material with in-situ formed LaH3 and its hydrogen storage characteristics

Abstract

In this work, a Mg-based composite material with in-situ formed LaH3, Mg2NiH4-LiBH4 + 20 wt% LaH3, was prepared by ball milling LiBH4 and hydrogenated LaMg2Ni and Mg2Ni powder mixture, followed by heat treatment at 573 K. The onset dehydrogenation temperature of the composite is reduced by 50 K compared with that of Mg2NiH4-LiBH4. The LaH3-doped composite shows faster kinetics, absorbing 1.43 wt% hydrogen within 100 s at 423 K, which is 6.5 times faster than Mg2NiH4-LiBH4. Moreover, the composite releases 1.24 wt% hydrogen within 500 s at 573 K, 0.69 wt% higher than Mg2NiH4-LiBH4. The activation energy of the composite is reduced by 8.2 and 80 kJ/mol compared with that of Mg2NiH4-LiBH4 and commercial MgH2, respectively. The improvement in hydrogen storage properties is attributed to the fact that LaH3 promotes the generation of nano-sized spongy Mg structure, which has good catalytic activity during the subsequent hydrogenation/dehydrogenation process.