Improved hydrogen storage performance of as-milled Sm–Mg–Ni alloy by adding CeO₂

To investigate the influence of adding CeO₂ on the hydrogen storage characteristics of Sm–Mg–Ni-based SmMg₁₁Ni-type alloy, mechanical milling was utilized to synthesize SmMg₁₁Ni and SmMg₁₁Ni + 5 wt.% CeO₂ (named SmMg₁₁Ni–5CeO₂) alloys. The microstructure of as-cast and as-milled samples was measured via X-ray diffractometer and transmission electron microscope. Sieverts device was utilized to measure the isothermal hydriding and dehydriding kinetics. The non-isothermal dehydrogenation performance was explored by thermogravimetry and differential scanning calorimetry. The hydrogen desorption activation energy of the compound metal hydride can be computed by both Arrhenius and Kissinger methods. The related data show that adding CeO₂ can engender a very slight influence on the hydrogen storage thermodynamics, but it can result in an obvious reduction in hydrogen absorption and desorption capacities. Furthermore, the hydrogen desorption performance of experimental alloys is conspicuously ameliorated by the addition of CeO₂, viz. lowering the initial hydrogen desorption temperature and enhancing hydrogen desorption rate. The hydrogen desorption activation energies with and without CeO₂ addition are 84.28 and 100.31 kJ/mol, respectively, with an obvious decrease of 16.03 kJ/mol. This is thought to be responsible for the ameliorated hydrogen desorption kinetics by adding CeO₂.