Abstract:

Bismuth tungstate/graphitic carbon nitride (Bi₂WO₆/g-C₃N₄) composite photocatalyst modified by Bi₂WO₆ quantum dots and nanosheets was prepared through ultrasonic-hydrothermal method using sodium oleate as auxiliary reagent. The compositions, structures and light absorption properties of Bi₂WO₆/g-C₃N₄ were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), Brunauer-Emmett-Teller (BET) and other techniques. The mechanism of synthetic reaction was proposed. Photocatalytic reduction of aqueous rhodamine B (RhB) was employed to assess the visible light photocatalytic activity of Bi₂WO₆/g-C₃N₄. Electrochemical impedance spectroscopy (EIS) and photocurrent characteriations demonstated that Bi₂WO₆/g-C₃N₄ with the heterogeneous interface separated the photo-generated electron-hole paris effectively. Hence, a rapid RhB degradation by Bi₂WO₆/g-C₃N₄-30(the number 30 represents the mass fraction(%) of g-C₃N₄) under visible light irradiation was achieved at 95.8% in 120 min. The results confirmed that the photogenerated holes were main active specie in the photodegradation process. Moreover, the relationship of heterogenrous interface and photocatalytic performance was investigated, and involved photocatalytic mechanism was revealed.

Key words: surface modification, bismuth tungstate/graphitic carbon nitride composite catalyst, visible light photocatalysis, mechanism of synthesis reaction and photocatalytic reaction