Pressure-Induced Engineering of Surface Oxygen Vacancies on Metal Oxides for Heterogeneous Photocatalysis

Abstract

Oxygen vacancies (OVs) spatially confined on the surface of metal oxide semiconductors are advantageous for photocatalysis, in particular, for O₂-involved redox reactions. However, the thermal annealing process used to generate surface OVs often results in undesired bulk OVs within the metal oxides. Herein, a high pressure-assisted thermal annealing strategy has been developed for selectively confining desirable amounts of OVs on the surface of metal oxides, such as tungsten oxide (WO₃). Applying a pressure of 1.2 gigapascal (GPa) on WO₃ induces significant lattice compression, which would strengthen the W–O bonds and increase the diffusion activation energy for the migration of the O migration. This pressure-induced compression effectively inhibits the formation of bulk OVs, resulting in a high density of surface-confined OVs on WO₃. These well-defined surface OVs significantly enhance the photocatalytic activation of O₂, facilitating H₂O₂ production and aerobic oxidative coupling of amines. This strategy holds promise for the defect engineering of other metal oxides, enabling abundant surface OVs for a range of emerged applications.