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

摘要

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 cOH 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.