Designed synthesis of a novel BiVO₄-Cu₂O-TiO₂ as an efficient visible-light-responding photocatalyst.

A novel visible-light-responding BiVO4-Cu2O-TiO2 ternary heterostructure composite was successfully fabricated via the preparation of BiVO4-TiO2 followed by coupling with Cu2O through facile wet chemistry methods based on the strategy of energy gap engineering. The as-fabricated composite was characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, UV-vis diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. Benefited from the rational design and construction, BiVO4-Cu2O-TiO2 exhibits a significantly enhanced photocatalytic activity for the degradation of rhodamine B (RhB) under the visible-light irradiation as compared with Cu2O and Cu2O-TiO2. Specifically, under the irradiation with an ordinary 9 W energy-saving fluorescent lamp for 8h, the photocatalytic degradation ratio of RhB for 5 wt%BiVO4-40 wt%Cu2O-TiO2 reaches 97.8%. The enhanced photocatalytic activity of BiVO4-Cu2O-TiO2 can be ascribed to the matched band edge positions of BiVO4, Cu2O and TiO2, the heterojunction formations among them as well as the lower charge transfer resistance, favoring the separation of the photo-generated electron-hole pairs. A possible mechanism of the visible-light photocatalytic degradation of RhB is also proposed.