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

Three Mg3REMg3RE (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 Mg3REMg3RE compounds have the D03D03 structure. The lattice constants of Mg3LaMg3La, Mg3MmMg3Mm and Mg3NdMg3Nd phases are 0.7498, 0.7451 and 0.7390 nm, respectively. The lattice constants of the new hydride phases formed from Mg3LaMg3La and Mg3NdMg3Nd 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 Mg3LaMg3La, Mg3MmMg3Mm and Mg3NdMg3Nd alloys are 2.89, 2.58 and 1.95 wt%, respectively. The enthalpy (ΔH)(ΔH) and entropy (ΔS)(ΔS) of Mg3RE–HMg3RE–H dehydriding reaction were also determined. Hydrogen absorption kinetic curves measured at room temperature could be well fitted by the Avrami–Erofeev equation.