Structure modification of magnesium hydride for solid hydrogen storage

Hydrogen has received widespread attention as a clean future energy source. However, the key challenge to enable hydrogen as an energy vector is its storage. When comparing the various hydrogen storage methodologies, solid hydrogen storage using metal hydrides is quite attractive due to its high Volumatic energy density and high safety. In this review, we comprehensively discuss the critical importance of structural optimization, such as increasing porosity, for magnesium-based hydrogen storage materials. This aspect has been inadequately addressed and incompletely covered in previous works. Specifically, we present the hydrogen storage mechanisms by solid materials, particularly metal materials, along with their kinetic and thermodynamic principles. Additionally, synthesis methods of these materials using ball milling, thin film deposition, and direct current plasma technology are systematically classified and described. Performance improvements of Mg-based alloys or composites through catalysis, alloying and nanosizing were screened and concluded. Finally, porous-structure based improvements for Mg-based materials are emphasized, including Mg porous films, Mg metal-organic framework sand Mg-based nanoconfined materials. This study concludes that a bio-inspired technique for creating porous magnesium skeletons shows significant potential and advantages. Additionally, a casting method incorporating ultrasound is identified as an efficient solution for large-scale production. These technological innovations can replace expensive rare earth elements while achieving similar effects.