Hydrothermal synthesis of graphitic carbon nitride–BiVO4 composites with enhanced visible light photocatalytic activities and the mechanism study

• C3N4–BiVO4 composites with high photocatalytic activity were successfully synthesized through a facile hydrothermal method.
• C3N4–BiVO4 samples were characterized by various characterization technologies.
• C3N4–BiVO4 samples presented outstanding visible-light-induced photocatalytic performance.

Novel graphitic carbon nitride (C3N4) and bismuth vanadate (BiVO4) composite photocatalysts were successfully synthesized by a facile hydrothermal method. The scanning electron microscopy (SEM) revealed that an intimate interface between C3N4 and BiVO4 formed in the composites. Compared with the pure C3N4 and BiVO4, the C3N4–BiVO4 photocatalysts showed remarkably the higher photocatalytic activities in degrading rhodamine B (Rh B). The best active heterojunction proportion was 0.5C3N4–0.5BiVO4. Over this catalyst, the 100% degradation of Rh B (0.002 mmol L−1) was obtained under visible light irradiation (λ>420 nm) for 40 min. The active species in Rh B degradation were examined by adding a series of scavengers. The study on photocatalytic mechanism revealed that the electrons injected directly from the conduction band of C3N4 to that of BiVO4, resulting in the production of superoxide radical (O2
• −) and hydroxyl radical (OH
• ) in the conduction band of BiVO4. Simultaneously, the rich holes in the valence band of g-C3N4 oxidized Rh B directly to promote the photocatalytic degradation reaction.

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