Recent advances in catalyst-modified Mg-based hydrogen storage materials

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.