Synergistic enhancement of hydrogen storage performance in Mg2Ni alloys via Sm doping and hierarchical porosity

Mg 2 Ni alloys face sluggish kinetics and high operating temperatures for hydrogen storage. This study employs a synergistic strategy of porosity engineering and Sm doping. Porous Mg 2 Ni and Sm x Mg 2- x Ni alloys are synthesized using NH 4 HCO 3 as a pore-forming agent. The optimized porous Mg 2 Ni achieves rapid absorption (3.1 wt% within 100 s at 200 °C) and lowers the initial desorption temperature to 223 °C without ball milling. Sm doping forms catalytic Sm 3 H 7 , enhancing hydrogen transport and reducing the dehydrogenation barrier. The best composition, Sm 0.05 Mg 1.95 Ni, exhibits initial and peak desorption temperatures of 220 °C and 306 °C, an activation energy of 51.24 kJ mol −1 , and >95% capacity retention after 10 cycles. This work demonstrates that combining porous structure with Sm doping catalysis is an effective strategy to enhance Mg 2 Ni-based hydrogen storage materials.