Preparation, characterization and enhanced visible-light photocatalytic activities of BiPO4/BiVO4 composites

BiPO4/BiVO4 composites with different P/V molar ratios were prepared by the hydrothermal method and the effect of pH values of hydrothermal reaction on photocatalytic activity of BiPO4/BiVO4 composite was investigated. The photocatalysts were characterized by X-ray diffraction, field emission scanning electron microscopy, energy-dispersive spectroscopy, X-ray photoelectron spectroscopy and UV–vis diffuse reflectance spectroscopy. The photocatalytic property of BiPO4/BiVO4 was evaluated by photocatalytic degradation of Methylene blue under visible light irradiation. The results showed that the photocatalytic activity of the composites was much higher than that of pure BiPO4 and BiVO4. The rate constant of Methylene blue degradation over BiPO4/BiVO4 (P/V molar ratio of 5:1 and hydrothermal reaction pH value of 1.5) is 1.7 times that of pure BiVO4. The photocatalytic activity enhancement of BiPO4/BiVO4 composite is closely related to the BiVO4 functioning as a sensitizer to adsorb visible light and the heterojunction of BiPO4/BiVO4 acting as an active center for hindering the rapid recombination of electron–hole pairs during the photocatalytic reaction.