Hydrogen Storage of Mg Under an Ultralow Pressure of 1 Bar

Magnesium hydride (MgH 2 ) has been regarded as an attractive candidate for solid-state hydrogen storage, yet its practical applications are limited by the requirement of elevated temperatures and sluggish hydrogen uptake and release kinetics. Herein, TiO 2 polyhedral frameworks with uniformly distributed V 2 O 5 (denoted as V 2 O 5 /TiO 2 ) are constructed to improve hydrogen storage performance of Mg/MgH 2 . During the reversible hydrogenation and dehydrogenation process, metallic V and Ti along with low-valent Ti- and V-based oxides are in situ formed. Among them, metallic V supported on TiO 2 exhibits the lowest hydrogen adsorption energy, enabling superior catalytic performance over TiO 2 and V 2 O 5 . As a result, the peak dehydrogenation temperature of MgH 2 decreases to 215°C, 105°C lower than that of pristine MgH 2 , with a decrease of the apparent activation energy from 139.50 kJ·mol −1 to 68.99 kJ·mol −1 . Moreover, electron migration from V toward TiO 2 leads to charge accumulation around Ti and O atoms, shifting the V 3 d -band center toward the Fermi level and thereby improving the catalytic function of V's d-electrons, facilitating hydrogen dissociation without energy barriers. Therefore, the V 2 O 5 /TiO 2 -catalyzed Mg absorbs 4.12 wt% H 2 under an ultralow pressure of 1 bar at 25°C. This provides a new strategy for developing advanced Ti and V-based catalysts for mild-condition hydrogen storage of MgH 2 .