Study of the role of oxygen vacancies as active sites in reduced graphene oxide-modified TiO₂

In recent years, substantial efforts have been devoted to exploring reduced graphene oxide/TiO₂ (RGO/TiO₂) composite materials; however, there is still a paucity of reports on the construction of reduced graphene oxide/TiO₂ with oxygen vacancies (RGO/TiO₂-OV) via a facile two-step wet chemistry approach. In this work, we show a proof-of-concept study follow RGO introduced into TiO₂ with oxygen vacancies, the role of oxygen vacancies as active sites in reduced graphene oxide-modified TiO₂. The photocatalytic performance and related properties of blank-TiO₂, blank-TiO₂ with oxygen vacancies (blank-TiO₂-OV), RGO/TiO₂, and RGO/TiO₂-OV were comparatively studied. It was found that due to the incorporation of RGO, RGO/TiO₂ and RGO/TiO₂-OV exhibit a higher photocatalytic performance under simulated solar light irradiation than their counterparts without rGO. More importantly, it was found that blank-TiO₂ has a higher photocatalytic activity than blank-TiO₂-OV under simulated solar light irradiation. However, RGO/TiO₂ shows a lower photocatalytic activity than rGO/TiO₂-OV. By a series of combined techniques, we found that the introduction of a component, such as RGO, with the matched energy band to TiO₂ could lead to the formation of a long-lived electron-transfer state, thus prolonging the lifetime of the photogenerated charge carriers. Furthermore, during the photocatalytic process, RGO could tune the role of oxygen vacancies in TiO₂ from recombination centers to active sites. These findings are of great significance for the design of effective photocatalytic materials in the field of solar energy conversion.