Hydrogen Storage of Mg Under an Ultralow Pressure of 1 Bar

ABSTRACT 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 .