Hydrogen Storage in Mg–Ni-Type Alloys with La and Sm Incorporation

The addition of rare earth elements lanthanum and samarium to Mg–Ni-type alloys enhanced the hydrogen absorption and desorption kinetics. The microstructures of these alloys were characterized by using XRD, SEM, TEM, HTREM, and SAED methods. PCT equipment was employed to test the hydrogen storage performance. It was observed that Mg96NiLa3 alloys exhibited a more uniform and refined phase distribution, credited to the grain refinement effect triggered by Mg17La2. Additionally, the Mg96NiLa3 alloy demonstrated a significant hydrogen storage capacity, with hydrogen release reaching 6.2 wt % at 593 K, compared to 5.4 wt % for the Mg96NiSm3 alloy at the same temperature. The activation energies of dehydrogenation for Mg96NiLa3 and Mg96NiSm3 were 99.69 and 97.53 kJ/mol, respectively, with no significant difference considering errors. Similarly, the enthalpies of dehydrogenation were 72.9 kJ/mol of H2 for Mg96NiLa3 and 78 kJ/mol of H2 for Mg96NiSm3, indicating no notable distinction in the thermodynamic properties of the two alloys. Thus, the enhancement of the thermodynamic properties of Mg–Ni-type alloys by rare earth elements La and Sm appears to be insignificant.