A new type of Mg-based metal hydride with promising hydrogen storage properties

Three Mg 3 RE (rare earth abbreviated as RE) compounds were prepared in Mg–La, Mg–Nd and Mg–misch metal (abbreviated as Mg–Mm) systems by induction melting. XRD patterns show that the as melted Mg 3 RE compounds have the D 0 3 structure. The lattice constants of Mg 3 La , Mg 3 Mm and Mg 3 Nd phases are 0.7498, 0.7451 and 0.7390 nm, respectively. The lattice constants of the new hydride phases formed from Mg 3 La and Mg 3 Nd during the hydrogenation process with fcc structure are 0.5607 and 0.5598 nm, respectively. The alloys have good hydrogen storage properties and could absorb hydrogen at room temperature with rapid hydriding and dehydriding kinetics. The maximum hydrogen absorption content of Mg 3 La , Mg 3 Mm and Mg 3 Nd alloys are 2.89, 2.58 and 1.95 wt%, respectively. The enthalpy ( Δ H ) and entropy ( Δ S ) of Mg 3 RE – H dehydriding reaction were also determined. Hydrogen absorption kinetic curves measured at room temperature could be well fitted by the Avrami–Erofeev equation.