Collaborative Optimization of Hydrogen Storage Properties via Self-Formation of Bimetallic Oxide and Electron Buffering of Sc: An Air-Stable MgSc-TiO₂ Composites

The oxidation resistance is the key to coordinating the high reactivity and environmental sensitivity of Mg-based hydrogen storage materials. Herein, an MgSc-TiO₂ composite is constructed through a strategy combining alloying and compositing. The results indicate that α-Mg phase remains stable without detectable oxidation after 6 months of air exposure, with only a small amount of MgSc₂O₄ being formed, and excellent hydrogen storage performance is obtained. The reversible capacity reaches 5.86 wt.% at 320°C, with the dehydrogenation activation energy significantly reduces to 117.9 kJ/mol from 144.0 kJ/mol. In particular, it can absorb 2.74 wt.% at 200°C under a low hydrogen pressure of 0.2 MPa. The reaction kinetics are markedly improved by the combination effect of stable interfacial catalytic phase, dynamic cyclic Ti valence state and oxygen vacancies. DFT calculations reveal the synergistic oxidation inhibition mechanism between Sc and Ti from the electronic structure level. The electron buffering effect of Sc and the competitive absorption of Ti and Sc sites efficiently prevent the oxidation of Mg. This theory provides an innovative basis for the design of high-stability Mg-based hydrogen storage materials.