Oxygen Vacancy-Rich 2D TiO Nanosheets: A Bridge Toward High Stability and Rapid Hydrogen Storage Kinetics of Nano-Confined MgH.

MgH 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 TiO nanosheets with abundant oxygen vacancies are used to fabricate a flower-like MgH/TiO heterostructure with enhanced hydrogen storage performances. Particularly, the onset hydrogen desorption temperature of the MgH/TiO heterostructure is lowered down to 180 °C (295 °C for blank MgH). The initial desorption rate of MgH/TiO reaches 2.116 wt% min at 300 °C, 35 times of the blank MgH 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 MgH-TiO 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 MgH NPs confined by TiO 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.