Magnesium-Based Metal Hydrides for Solid-State Hydrogen Storage: Materials, Methods, and Challenges

Magnesium-based metal hydrides have become attractive options for solid-state hydrogen storage because of their high gravimetric capacity, affordability, environmental friendliness, and natural abundance. According to the paper, one of the most appealing light-metal hydrides is pure magnesium hydroxide (MgH₂), which has a potential hydrogen storage capacity of up to 7.6 wt.%. High thermodynamic stability, slow hydrogen sorption kinetics, and high operating temperatures, however, significantly restrict its practical application. Pure magnesium/MgH₂, magnesium-based alloys, transition metal composites, and complicated hydrides are only a few of the magnesium-based hydrogen storage methods that are covered in this paper. The study methodically looks at many approaches such as alloying, catalytic doping, nanostructuring, and sophisticated production methods that have been developed to get around inherent limits. Alloying with elements such as Ni, Ti, and Fe alters thermodynamic properties and lowers desorption temperatures. Mg₂NiH₄ systems show lower hydrogen release temperatures (~250 °C) compared to MgH₂ (~350 °C). Similarly, by promoting hydrogen dissociation and diffusion, transition metal catalysts like Nb₂O₂ and TiCl₃ greatly improve the kinetics of hydrogen sorption. By boosting defect density, reducing diffusion routes, and increasing surface area, nanostructuring further enhances performance and accelerates absorption/desorption behavior. Key synthesis techniques, including as ball milling, chemical reduction, solution-based procedures, and vapor deposition, are also included in the review, with an emphasis on their impact on microstructure and hydrogen storage qualities. The trade-offs between capacity, kinetics, and thermodynamic stability across several Mg-based systems are illustrated. Overall, this review emphasizes how important it is to optimize Mg-based hydrides using a combination of tactics, namely, alloying, catalysis, and nanoscale engineering. Despite tremendous advancements, issues with operating temperature, cycling stability, and scalability still exist, requiring more investigation for useful hydrogen storage applications.