Room-Temperature Transient Hydrogen Uptake of MgH₂ Induced by Nb-Doped TiO₂ Solid-Solution Catalysts

The practical applications of MgH₂ as a high-density hydrogen carrier depend heavily on efficient and low-cost catalysts to accelerate the dehydriding/hydriding reactions at moderate temperatures. In the present work, this issue is addressed by synthesizing Nb-doped TiO₂ solid-solution-type catalysts that dramatically improve the hydrogen sorption performances of MgH₂. The catalyzed MgH₂ can absorb 5 wt % of H₂ even at room temperature for 20 s, release 6 wt % of H₂ at 225 °C within 12 min, and the complete dehydrogenation can be achieved at 150 °C under a dynamic vacuum atmosphere. Density functional theory calculations reveal that Nb doping introduces Nb 4d orbitals with stronger interaction with H 1s into the density of states of TiO₂. This considerably enhances both the adsorption and dissociation ability of the H₂ molecule on the catalysts surface and the hydrogen diffusion across the specific Mg/Ti(Nb)O₂ interface. The successful implementation of solid solution-type catalysts in MgH₂ offers a demonstration and inspiration for the development of high-performance catalysts and solid-state hydrogen storage materials.