Abstract: The storage of hydrogen in a compact, safe and cost-effective manner can be one of the key enabling technologies to power a more sustainable society. Magnesium hydride (MgH₂) has attracted strong research interest as a hydrogen carrier because of its high gravimetric and volumetric hydrogen densities. However, the practical use of MgH₂ for hydrogen storage has been limited due to high operation temperatures and sluggish kinetics. Catalysis is of crucial importance for the enhancement of hydrogen cycling kinetics of Mg/MgH₂ and considerable work has been focused on designing, fabricating and optimizing catalysts. This review covers the recent advances in catalyzed Mg-based hydrogen storage materials. The fundamental properties and the syntheses of MgH₂ as a hydrogen carrier are first briefly reviewed. After that, the general catalysis mechanisms and the catalysts developed for hydrogen storage in MgH₂ are summarized in detail. Finally, the challenges and future research focus are discussed. Literature studies indicate that transition metals, rare-earth metals and their compounds are quite effective in catalyzing hydrogen storage in Mg/MgH₂. Most metal-containing compounds were converted in situ to elemental metal or their magnesium alloys, and their particle sizes and dispersion affect their catalytic activity. The in-situ construction of catalyzed ultrasmall Mg/MgH₂ nanostructures (< 10 nm in size) is believed to be the future research focus. These important insights will help with the design and development of high-performance catalysts for hydrogen storage in Mg/MgH₂.

Key words: Hydrogen storage, Magnesium hydride, Kinetics, Catalysts, Reversibility