Highlights A comprehensive discussion of the recent advances in the nanostructure engineering of Mg-based hydrogen storage materials is presented. The fundamental theories of hydrogen storage in nanostructured Mg-based hydrogen storage materials and their practical applications are reviewed. The challenges and recommendations of current nanostructured hydrogen storage materials are pointed out.

MgH₂ has attracted intensive interests as one of the most promising hydrogen storage materials. Nevertheless, the high desorption temperature, sluggish kinetics, and rapid capacity decay hamper its commercial application. Herein, 2D TiO₂ nanosheets with abundant oxygen vacancies are used to fabricate a flower-like MgH₂/TiO₂ heterostructure with enhanced hydrogen storage performances. Particularly, the onset hydrogen desorption temperature of the MgH₂/TiO₂ heterostructure is lowered down to 180 °C (295 °C for blank MgH₂). The initial desorption rate of MgH₂/TiO₂ reaches 2.116 wt% min⁻¹ at 300 °C, 35 times of the blank MgH₂ under the same conditions. Moreover, the capacity retention is as high as 98.5% after 100 cycles at 300 °C, remarkably higher than those of the previously reported MgH₂-TiO₂ composites. Both in situ HRTEM observations and ex situ XPS analyses confirm that the synergistic effects from multi-valance of Ti species, accelerated electron transportation caused by oxygen vacancies, formation of catalytic Mg-Ti oxides, and stabilized MgH₂ NPs confined by TiO₂ nanosheets contribute to the high stability and kinetically accelerated hydrogen storage performances of the composite. The strategy of using 2D substrates with abundant defects to support nano-sized energy storage materials to build heterostructure is therefore promising for the design of high-performance energy materials.

MgH₂ is a promising high-capacity solid-state hydrogen storage material, while its application is greatly hindered by the high desorption temperature and sluggish kinetics. Herein, intertwined 2D oxygen vacancy-rich V₂O₅ nanosheets (H-V₂O₅) are specifically designed and used as catalysts to improve the hydrogen storage properties of MgH₂. The as-prepared MgH₂-H-V₂O₅ composites exhibit low desorption temperatures (T_onset = 185 °C) with a hydrogen capacity of 6.54 wt%, fast kinetics (E_a = 84.55 ± 1.37 kJ mol⁻¹ H₂ for desorption), and long cycling stability. Impressively, hydrogen absorption can be achieved at a temperature as low as 30 °C with a capacity of 2.38 wt% within 60 min. Moreover, the composites maintain a capacity retention rate of ~ 99% after 100 cycles at 275 °C. Experimental studies and theoretical calculations demonstrate that the in-situ formed VH₂/V catalysts, unique 2D structure of H-V₂O₅ nanosheets, and abundant oxygen vacancies positively contribute to the improved hydrogen sorption properties. Notably, the existence of oxygen vacancies plays a double role, which could not only directly accelerate the hydrogen ab/de-sorption rate of MgH₂, but also indirectly affect the activity of the catalytic phase VH₂/V, thereby further boosting the hydrogen storage performance of MgH₂. This work highlights an oxygen vacancy excited “hydrogen pump” effect of VH₂/V on the hydrogen sorption of Mg/MgH₂. The strategy developed here may pave a new way toward the development of oxygen vacancy-rich transition metal oxides catalyzed hydride systems.

A core–shell nanostructured Mg@Pt composite, consisting many of icosahedral Mg particles as the core with nano-sized Pt particles distributed homogeneously on different surfaces, was synthesized through an arc plasma method followed by the generic solid-state method. The microstructures and hydrogen sorption properties of the Mg@Pt composite were carefully investigated and compared to that of pure Mg powder. In particular, the dehydrogenation behaviors of the hydrogenated Mg@Pt composite were observed in situ via high-resolution transmission electron microscopy (HRTEM). The results revealed that the Pt on Mg particles showed a “spillover” effect to improve the hydrogen absorption kinetics in the early stage. It then transformed into H-stabilized Mg₃Pt, followed by the formation of MgH₂. DFT calculation and in situ TEM observations demonstrated that the H-stabilized Mg₃Pt acted as a “hydrogen pump” for the dehydrogenation of MgH₂ and then transformed into Pt after desorption. Through this effect, the dehydriding kinetics of the hydrogenated Mg@Pt composite was improved and the onset dehydrogenation temperature was reduced compared to that of the pure MgH₂ powder.