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

Graphical abstract: - Highlights: • BiPO₄/BiVO₄ composites were successfully prepared by the hydrothermal method. • BiPO₄/BiVO₄ composites exhibited broad absorption in the visible region. • Visible-light photocatalytic activities of BiPO₄/BiVO₄ composites were enhanced. • P/V molar ratio and pH value of the reaction affect photocatalytic activity. • The mechanism of enhanced visible-light photocatalytic activities was discussed. - Abstract: 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