Oxygen Vacancy Defect Engineering of Heterophase Junction TiO₂: Interfacial/Surface Oxygen Vacancies Coadjust the Photocatalytic ROS Production

In this study, TiO2 samples are synthesized through two stages including hydrolysis and calcination. It is found that the addition of HCl in the hydrolysis stage could facilitate the formation of heterophase junction TiO2. By annealing at 300 °C in an argon atmosphere, interfacial oxygen vacancies (Vo) and surface Vo (distributed in the anatase phase) can be constructed in the heterophase junction TiO2. After photocatalytic experiments, it can be found that surface Vo and interface Vo have a synergistic effect in the production of photocatalytic reactive oxygen species (ROSs). Surface Vo can enrich O2 and transmit electrons to O2 on the surface of anatase. Therefore, the enriched O2 can be converted into •O2– and 1O2 easily. The interfacial Vo not only facilitate the electron transmission between the two phases but also change the electron transfer mode from I-scheme to Z-scheme. Thus, interfacial Vo make photogenerated electrons transfer to anatase and photogenerated holes leave in the rutile. These holes in the rutile part have high oxidation potential and can better oxidize H2O (or OH–) molecules to •OH. They can also oxidize •O2– to 1O2. This work promotes the further development of defect design and application in photocatalytic materials.