Efficient hydrogen storage with nanocrystalline mg–ni alloy: enhanced absorption and kinetics via mechanochemical synthesis

A simple and environmentally friendly flux-free vacuum casting followed by brief high-energy ball milling was employed to produce nanocrystalline Mg–Ni alloys suitable for hydrogen storage. The alloy primarily formed the Mg₂Ni phase, with a crystallite size of 38.6 nm, as confirmed by X-ray diffraction. Upon hydrogenation, Mg2Ni transformed predominantly into Mg2NiH4, with additional MgH2 formation, demonstrating efficient hydrogen absorption. Field emission scanning electron microscopy revealed significant microstructural changes during hydrogenation, enhancing hydrogen diffusion. Nitrogen adsorption/desorption isotherms showed a fourfold increase in specific surface area post-hydrogenation, from 3.85 to 15.32 m2/g. The alloy achieved a maximum hydrogen storage capacity of 3.54 wt.% at 573 K, with enhanced absorption kinetics after activation. These results highlight the potential of Mg–Ni alloys for hydrogen storage, emphasizing the importance of optimized synthesis and activation processes for enhanced performance and stability.