The roles of conjugations of graphene and Ag in Ag3PO4-based photocatalysts for degradation of sulfamethoxazole

To achieve efficient degradation of sulfamethoxazole (SMX), a typical antibiotic compound that may negatively affect water quality once it enters the environment, three different photocatalysts, namely, silver phosphate (Ag3PO4; AGP), Ag3PO4-graphene (AGP-G) and Ag/Ag3PO4-graphene (AAGP-G), were fabricated by a chemical precipitation approach. The photocatalysts were characterized by field emission scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) analysis and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS). The adsorption and photocatalytic decomposition of SMX by AGP, AGP-G and AAGP-G under simulated solar light irradiation were investigated. It was found that AGP-G and AAGP-G did not exhibit better photocatalytic activities for the degradation of SMX than pure AGP, but the coupling of graphene and Ag enhanced the structural stability of AGP, which indicated that AGP-G and AAGP-G were more practical to use in real treatment processes. The important result of this study is that the pathway of electron transfer for the degradation of SMX was different from that for dye photosensitizers reported in previous studies. This study may provide new insights into composite photocatalytic materials for the design of highly efficient reaction systems.