Enhancing hydrogen storage in Mg alloys: Role of alloying, reinforcements, and severe plastic deformation techniques

Magnesium and its alloys have emerged as potential candidates for solid state storage of hydrogen owing to its higher theoretical capacity of ∼7.6 wt%, abundance and lightweight nature. However, their practical application is hindered by slow hydrogenation kinetics, high thermal stability of hydrides and poor cycling performance. This review comprehensively discusses strategies to overcome these limitations that focusing on alloying, incorporation of catalytic reinforcements and the application of severe plastic deformation (SPD) techniques. Alloying with transition and rare-earth metals modifies thermodynamics and promotes reversible hydrogen storage while nanostructured reinforcements enhance diffusion pathways and catalytic activity. SPD techniques such as Friction Stir Processing (FSP), Accumulative roll bonding (ARB), Equal Channel Angular Pressing (ECAP), High Pressure Torsion (HPT), and cold rolling significantly refines the size of grain and also initiates lattice defects which accelerates the hydrogen sorption kinetics and improves structural stability. Synergistic effects of alloying, reinforcement and SPD are critically analysed along with their influence on thermodynamic destabilization and kinetic enhancement. The review also highlights the key challenges including process scalability, thermal management and long-term stability and also offers future perspectives to the fabrication of high-performance Mg based hydrogen storage systems.