Role of active oxygen species in the liquid-phase photocatalytic degradation of RhB using BiVO4/TiO2 heterostructure under visible light irradiation

Abstract

The systematic clarification of the photocatalytic process is an indispensable basis for the in-depth understanding of the photocatalytic mechanism. Various types of active oxygen species involved into the photocatalytic process have been investigated extensively, including OH and O2−, but still remain obscure and controversial. Herein, the roles of the active oxygen species generated in the liquid-phase photocatalytic degradation of RhB using BiVO4/TiO2 heterostructure under visible light irradiation are discussed in detail. The results revealed that the liquid-phase photocatalytic degradation behavior was greatly affected by the amount of BiVO4. When the loading BiVO4 was less than 9wt%, the de-ethylation of RhB on BiVO4/TiO2 was observed. While, the direct oxidative degradation of RhB took place in the BiVO4/TiO2/RhB system loaded with more BiVO4 (>9wt%). Particularly, 9% BiVO4/TiO2 enhanced the photosensitized degradation of RhB, and the degradation efficiency was 80% which was 1.14 times than that of pure TiO2. Combined with different surface analysis techniques (EPR, photoluminescence technique, etc.), it was found that O2− and OH were the key active species when the loading BiVO4 was less than 9wt%, while in the 50% BiVO4/TiO2/RhB system, O2− and holes played much more roles. Our findings provide certain theoretical guidance in understanding the functional mechanism of heterostructured photocatalysts, which can pave the way to further improve the concentration of the active species and design novel efficient photocatalysts.