Oxygen vacancy mediated charge transfer expediting over GQDs/TiO2 for enhancing photocatalytic removal of Cr (VI) and RhB synchronously

Abstract Understanding the underlying transport mechanism of photogenerated carriers is crucial in designing active heterojunctions in the field of photocatalysis. In this study, the redox activity of Graphene quantum dots/TiO2 (GQDs/TiO2) hybrid was investigated through water treatment under visible light irradiation. The corresponding findings showed that the charge transfer between GQDs and TiO2 accompanied with oxygen vacancy (Vo) was expedited, resulting in enhanced redox activity in the Cr (VI) and RhB co-removing system. Further investigation revealed that Vo introduced a defect level in TiO2 just below its conduction band that could induce visible light excitation while leading to quick charge separation and effective transmission from GQDs to TiO2. Therefore, carrying out photocatalytic Cr (VI) reduction and RhB degradation synchronously over GQDs/TiO2 can roughly enhance 2 and 3 times pure TiO2 nanosheets under visible light irradiation. The findings of this study may provide novel insight into heterojunction engineering and defect level controlling in order to attain efficient photocatalyst and offer additional prospects for photocatalytic applications.