Tuning the thermodynamics and kinetics of magnesium-based materials for hydrogen energy storage: a review

Developing efficient hydrogen storage techniques will be vital in constructing a hydrogen energy society. Magnesium hydride shows massive potential in the hydrogen storage field because of its merits of high hydrogen storage capacity, good cyclic durability, and reasonable cost. However, its stable thermodynamics and sluggish kinetics obstruct the magnesium hydride system's practical application. Numerous attempts have been implemented to improve the hydrogen storage properties of this system, which are reviewed in this work systematically. This work aims to provide a way to evaluate and compare the improvements in hydrogen storage properties of the Mg/MgH₂ system and offer an intuitive perspective for the development of a highly efficient energy storage system. Several methods, such as catalyst additions, complex formation by alloying, composite formation, size reduction, and morphology modification through physicochemical treatment, are summarized and compared. Catalyst additions are the most effective in enhancing kinetics, while complex formation enables hydrogen storage under milder conditions. Physicochemical treatments improve kinetics by reducing reactant size and shortening diffusion pathways. Nanostructuring shows promise but requires further stability improvements. However, no single technique satisfies all requirements for practical applications. Further progress should be considered to combine different methods and adopt a cost-effective and easy way to tune the properties of the Mg/MgH₂ system. Finally, the prospective strategy for the future improvements of the Mg hydride-based hydrogen storage system is discussed.