Z-scheme mechanism of photogenerated carriers for hybrid photocatalyst Ag3PO4/g-C3N4 in degradation of sulfamethoxazole.

Composite or hybrid photocatalysts are gaining increasing interests due to the unique and enhanced photocatalytic activity. In this study, Ag3PO4/g-C3N4 with different ratios of Ag3PO4 and g-C3N4 were synthesized using a facile in situ precipitation method. The photocatalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction pattern (XRD), Fourier transform infrared spectra (FTIR), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS). The photocatalytic performance was evaluated by the degradation of sulfamethoxazole (SMX), a model antibiotic compound, under visible light irradiation. It was found that the composite photocatalyst Ag3PO4/g-C3N4 with a mass ratio of Ag3PO4:g-C3N4 of 98:2 exhibited a higher photocatalytic activity than Ag3PO4/g-C3N4 with the mass ratio of 2:98 for the degradation of SMX. When Ag3PO4 was the primary part of Ag3PO4/g-C3N4 photocatalyst, the migration of photogenerated electron-hole showed a Z-scheme mechanism with photongenerated holes on the valance band of Ag3PO4 to oxidize pollutants. The separation mechanism was investigated by the photoluminescence technique and the scavengering of reactive oxygen species.