Hydrothermal synthesis and visible light photocatalytic activity enhancement of BiPO4/Ag3PO4 composites for degradation of typical dyes

Abstract

BiPO4/Ag3PO4 composites were synthesized by the hydrothermal method and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), and UV–vis diffuse reflectance spectroscopy (DRS). The effects of Bi/Ag molar ratios and pH values of hydrothermal reaction on photocatalytic activity of BiPO4/Ag3PO4 composites were investigated. The photocatalytic property of BiPO4/Ag3PO4 was evaluated by photocatalytic degradation of methylene blue (MB) and methyl orange (MO) under visible light irradiation (λ>420nm). The results showed that the photocatalytic degradation efficiency of MB by BiPO4/Ag3PO4 composite with Bi/Ag molar ratio of 4:3 synthesized at pH 7 of hydrothermal reaction attains 99.2%, which is much higher than that (83.3%) by mathematical sum of those of Ag3PO4 and BiPO4 containing the same weight of visible-light active component after visible light irradiation for 2h, and the rate constant of the composite is 2.46 times that of sum of those of Ag3PO4 and BiPO4. High stability of the BiPO4/Ag3PO4 composite under visible light was proved. A similar high activity of MO was also found. In addition, the quenching effects of different scavengers proved that reactive h+ and O2− played major role in dye degradation. The visible light photocatalytic activity enhancement of the BiPO4/Ag3PO4 composite came from the sensitization of Ag3PO4 and the efficient separation of electron–hole pairs, which resulted from the p–n heterojunction of BiPO4/Ag3PO4. These results indicate that there is a significant potential for the BiPO4/Ag3PO4 composite as a photocatalyst in the degradation of organic contaminants under visible light.