Recent progress on enhancing the hydrogen storage properties of Mg-based materials via fabricating nanostructures: A critical review

The on-board hydrogen storage needs light, compact, and affordable system to replace the compressed hydrogen tanks. MgH₂ is regarded as one of the most promising candidates for solid-state hydrogen storage. Due to the thermodynamically stable Mg-H bond, the poor dissociation ability of H₂ molecules and recombination ability of H atoms on Mg surface, and the low diffusion coefficient of H atoms in Mg, especially in MgH₂, there remains a challenge to design a material capable of absorbing and desorbing hydrogen rapidly at moderate temperatures. Herein, common strategies to improve the hydrogen storage properties of Mg-based materials are introduced. Some recent studies for overcoming the thermodynamic and kinetic barriers are reviewed, especially the approaches to fabricate nanostructure in Mg-based materials. The nanometric crystals or particles are synthesized by mechanical deformation, reduction in solution, physical/chemical vapor deposition, interface confinement. The nano-catalyst can be decorated by external doping or in-situ synthesis. In particular, the thermodynamic/kinetic parameters for hydrogenation and dehydrogenation are provided, and the mechanisms for the enhanced properties are summarized. The principles of structural design and catalytic decoration are discussed, and challenges and perspectives of fabricating nanostructures in Mg-based hydrogen storage materials are proposed.