MgH₂ shows significant potential for a solid-state hydrogen storage medium due to the advantages of high hydrogen capacity, excellent reversibility, and low cost. However, its large-scale application still requires overcoming significant thermodynamic and kinetic hurdles. Catalyst design and optimization enhancements are crucial for the hydrogen storage properties of MgH₂, wherein single-atom catalysts, characterized by their small size and high proportion of unsaturated coordination sites, have recently demonstrated a significant advance and considerable promise in this regard. This review presents recent progress on state-of-the-art single-atom catalysts for enhancing MgH₂ hydrogen storage, examining both supported and unsupported catalyst types, i.e., transition metal @ N-modified carbon materials and transition metal @ transition metal compounds, and metallene-derived compounds and single-atom alloys, respectively. We systematically discussed the single-atom catalysts in MgH₂ hydrogen storage systems, focusing on synthesis strategies, characterization techniques, catalytic mechanisms, as well as existing challenges and future perspectives. We aimed to provide a comprehensive and cohesive understanding for researchers in the field, and promote the development of single-atom catalysts and their significant optimization of the hydrogen storage performance of MgH₂.

Hydrogen storage is a key link in hydrogen economy, where solid-state hydrogen storage is considered as the most promising approach because it can meet the requirement of high density and safety. Thereinto, magnesium-based materials (MgH₂) are currently deemed as an attractive candidate due to the potentially high hydrogen storage density (7.6 wt%), however, the stable thermodynamics and slow kinetics limit the practical application. In this study, we design a ternary transition metal sulfide FeNi₂S₄ with a hollow balloon structure as a catalyst of MgH₂ to address the above issues by constructing a MgH₂/Mg₂NiH₄-MgS/Fe system. Notably, the dehydrogenation/hydrogenation of MgH₂ has been significantly improved due to the synergistic catalysis of active species of Mg₂Ni/Mg₂NiH₄, MgS and Fe originated from the MgH₂-FeNi₂S₄ composite. The hydrogen absorption capacity of the MgH₂-FeNi₂S₄ composite reaches to 4.02 wt% at 373 K for 1 h, a sharp contrast to the milled-MgH₂ (0.67 wt%). In terms of dehydrogenation process, the initial dehydrogenation temperature of the composite is 80 K lower than that of the milled-MgH₂, and the dehydrogenation activation energy decreases by 95.7 kJ·mol^–1 compared with the milled-MgH₂ (161.2 kJ·mol^–1). This method provides a new strategy for improving the dehydrogenation/hydrogenation performance of the MgH₂ material.