Catalytic Enhancement of Hydrogen Storage in MgH₂ Using Metal Oxide Catalysts: Recent Advances and Future Perspectives

In recent decades, significant efforts have been directed toward developing efficient hydrogen storage materials for sustainable energy applications. Magnesium hydride (MgH₂) is considered one of the most promising solid-state hydrogen storage materials due to its high theoretical hydrogen capacity (~7.6 wt%), abundance, low cost, and good reversibility. However, its practical application is limited by strong thermodynamic stability and sluggish hydrogen absorption/desorption kinetics, typically requiring temperatures above 300°C and exhibiting activation energies of ~200-210 kJ/mol. Among various strategies, catalyst incorporation has proven to be an effective approach to enhance hydrogen storage performance. In particular, metal oxide catalysts have attracted considerable attention due to their stability, availability, and strong catalytic activity. This review highlights recent advances in the catalytic enhancement of MgH₂ using metal oxide catalysts, with emphasis on transition metal oxides such as TiO₂, Fe₂O₃, NiO, Co₃O₄, and V₂O₅. The incorporation of these catalysts significantly improves hydrogen sorption behavior, reducing activation energy to ~114-136 kJ/mol (≈30-45% reduction) and lowering desorption temperatures by ~50-150°C. Optimized systems demonstrate hydrogen release capacities of ~4-6 wt% within 10-15 minutes at 250-300°C, while some catalysts (e.g., TiO₂-based systems) enable rapid hydrogen uptake of ~5.5 wt% within 5 minutes at 250°C. The key mechanisms, including enhanced hydrogen diffusion, defect formation, oxygen vacancy generation, and interfacial catalytic effects, are discussed. Furthermore, synthesis and modification strategies such as high-energy ball milling, nanostructuring, defect engineering, and hybrid catalyst design are examined in relation to their impact on performance. Recent developments in nanostructured, defect-rich, and multi-component catalyst systems demonstrate substantial improvements in kinetics, reversibility, and cycling stability. Despite these advancements, challenges related to scalability, cost, and long-term durability remain. Future research should focus on achieving hydrogen desorption below 200°C, reducing activation energy below 100 kJ/mol, and developing scalable synthesis routes, along with integration into renewable energy systems for practical MgH₂-based hydrogen storage applications.