Enhanced visible-light photoactivity of g-C3N4 via Zn2SnO4 modification

The objective of this research was to prepare, characterize and evaluate the photocatalytic activity of Zn2SnO4/g-C3N4 composite in RhB degradation under visible light irradiation. The composite was synthesized by simple calcination of Zn2SnO4-melamine mixture, and was characterized by various techniques including Brunauer-Emmett-Teller method (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), and photoluminescence spectroscopy (PL). Characterization results indicated that the decoration of Zn2SnO4 on g-C3N4 showed nearly no effect on its light absorption performance, but promoted the surface area of the composite, which benefited the adsorption of dyes and the subsequent photocatalytic process. However, more significant was the formation of hetero-junction structure between Zn2SnO4 and g-C3N4, which efficiently promoted the separation of electron-hole pairs and enhanced the photocatalytic performance of Zn2SnO4/g-C3N4. The optimal Zn2SnO4/g-C3N4 photocatalyst showed a degradation rate of 0.038 min−1, which was 3.2 times higher than that of g-C3N4. In addition, the Zn2SnO4/g-C3N4 composite shows high stability. O2− and h+ were the main reactive species.