Approaches for air stability, impurity resistance and safe containment of metal hydrides

Metal hydrides (MHs), which store hydrogen within a metal's crystal structure, provide a practical alternative to the extreme conditions needed to store compressed gas and cryogenic liquid, though at the cost of added weight. This review focuses on some critical technical challenges facing MHs in hydrogen storage applications: surface oxidation, pulverization, and the mechanical stresses induced during hydrogen cycling. Pulverization, an unavoidable consequence of hydrogen uptake by many hydrogen storage alloys, leads to powder agglomeration, densification, and compromised container safety while also increasing vulnerability to oxidation and impurity poisoning, which affects performance, kinetics, and capacity. Strategies to mitigate these problems include encapsulation with polymers and inorganic materials to prevent disintegration and shield hydride surfaces from impurity gases. Catalytic additions, alloying, and surface modifications are explored for enhancing oxidation tolerance. Additionally, improvements in hydride tank design are discussed, with attention to mechanical stability and stress management. This work highlights key material and engineering strategies that address the core limitations of MH-based hydrogen storage, with the goal of improving operational efficiency, safety, and overall system practicality. • Air stability, impurity tolerance and safe containment of metal hydrides are reviewed. • Reactivity, structural changes and scalability are discussed. • Material modifications by encapsulation, surface treatments and alloying are evaluated. • System-level interventions, including tank design and the use of additives, are discussed. • Trade-offs between different approaches are examined across hydride types.