Surface-Adsorbed Oxygen-Triggered Luminescence-Guided Defect Engineering of Oxygen Vacancy

Oxygen vacancies (O_v) in metal oxide-based materials can regulate their surface chemical and electronic properties, and thus the amount of O_v is crucial to exert their photo-, electro-, and thermocatalytic performances. Defect engineering has been introduced to prepare metal oxide-based materials with sufficient O_v. However, the current efforts have been hampered due to the failure to quantify the absolute values of O_v in metal oxide-based materials. In this work, we have prepared ZnFe oxides with varied O_v through the calcination of a ZnFe hydroxide precursor under the guidance of reaction-triggered luminescence induced by O_v. Hydrogen sulfide (H₂S), with the dual functionality of specific affinity toward metal oxides and low-temperature reducibility, has been utilized to react with O_v and interpret the O_v contents in ZnFe oxides. A stoichiometric relationship has been established between H₂S and surface-adsorbed oxygen (O_ad), leveraging the reversible interconversion between O_ad and O_v. Accordingly, the O_v contents in ZnFe oxides have been regulated, guided by the total luminescence integral areas of H₂S oxidation. The universality of the proposed luminescence strategy was verified by other metal oxide-based materials, such as ZnCo and MgFe oxides. Our work demonstrates a simple and rapid strategy to quantify the O_v contents in metal oxide-based materials, providing guidance for the precise modulation of O_v in metal oxide-based materials with a high catalytic performance.