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

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 (lambda > 420 nm). 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 2 h, 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 O-2(-) 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. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.