Highly efficient Ag6Si2O7/WO3 photocatalyst based on heterojunction with enhanced visible light photocatalytic activities

Abstract

Ag₆Si₂O₇/WO₃ photocatalysts were prepared by an ultrasound-assisted precipitation method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra (DRS) and photoluminescence (PL) spectroscopy. The effects of Ag₆Si₂O₇/WO₃ mole ratios on photocatalytic activity of Ag₆Si₂O₇/WO₃ were investigated. The results showed that the photocatalytic degradation efficiency of methylene blue (MB) by Ag₆Si₂O₇/WO₃ (1 : 1) attains 97.4%, which is much higher than that (87.3%) by sole Ag₆Si₂O₇ and that (14.0%) by sole WO₃ after visible light irradiation for 30 min, and the apparent rate constant is 1.59 times that of sole Ag₆Si₂O₇ and 44.6 times that of sole WO₃. Photocatalytic activities of different photocatalysts with the same weight of visible-light-active components were compared and showed that the rate constant of Ag₆Si₂O₇/WO₃ (1 : 1) is 2.88 times that of mathematical sum of Ag₆Si₂O₇ and WO₃. Moreover, rhodamine B (RhB), methyl orange (MO) and 2,4-dichlorophenol were also effectively degraded. After 3 recycling runs, the photocatalytic performance of the Ag₆Si₂O₇/WO₃ (1 : 1) was still effectively maintained. In addition, the quenching effects of different scavengers proved that the ˙OH plays important roles in the photocatalytic reaction under visible light irradiation. The visible light photocatalytic activity enhancement of the Ag₆Si₂O₇/WO₃ (1 : 1) came from the efficient separation of electron–hole pairs, which resulted from the heterojunction of Ag₆Si₂O₇/WO₃. These results indicate that Ag₆Si₂O₇/WO₃ heterojunction is highly efficient photocatalyst and there is a significant potential in the degradation of organic contaminants under visible light irradiation.