Enhanced photocatalytic mechanism of Ag3PO4 nano-sheets using MS2 (M = Mo, W)/rGO hybrids as co-catalysts for 4-nitrophenol degradation in water

A chemically modified Ag3PO4@MS2(M = Mo, W)/rGO composite was firstly synthesized via a liquid-exfoliation solvothermal method. The structure, morphology, optical properties and composition were characterized by Xray diffraction, FT-IR spectroscopy, scanning electron microscopy, UV-vis diffuse reflectance spectra and X-ray photoelectron spectroscopy, respectively. The characterization results indicated that compact structure could be obtained by using this typical method due to in-situ chemical modification, which could also control the sizes of Ag3PO4 nano-sheets by adding MS2/rGO hybrids. More importantly, the resultant Ag3PO4@MS2/rGO composite exhibited higher photocatalytic activity and stability toward the degradation of 4-nitrophenol than pure Ag3PO4 under sunlight irradiation. The stable structure of Ag3PO4@MS2/rGO was closely related with Z-scheme electronic structure and electrical conductivity of MS2/rGO hybrids, leading to a higher consumption and transfer of photogenerated electrons. However, by controlling the amounts of MS2/rGO hybrids, more stable but lower photocatalytic activity composites could be obtained. Further analysis found that the holes and center dot O-2(-) were the main reactive species involved in the photocatalytic degradation of 4-nitrophenol. In addition, possible photo catalytic degradation pathways of 4-nitrophenol were also proposed based on the identified intermediates. The findings of this work may provide a new method to design efficient composites for photocatalytic degradation of organic pollutants.