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.