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Oxygen vacancies (OVs) spatially confined on the surface of metal oxide semiconductors are advantageous for photocatalysis, in particular, for O 2 -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 (WO 3 ). Applying a pressure of 1.2 gigapascal (GPa) on WO 3 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 WO 3 . These well-defined surface OVs significantly enhance the photocatalytic activation of O 2, facilitating H 2 O 2 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.
Wang et al. (Wed,) studied this question.