Abstract: SiO₂/g-C₃N₄ composite powders were successfully prepared by calcination of proper as-prepared silicon dioxide (SiO₂) and melamine (C₃H₆N₆) composite precursors. The phase composition, morphology,optical absorption performance, and specific surface area of the composite powders were carried out by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), ultraviolet-visible light absorption spectrum (UV-Vis) andBET method. Results show that the average particle size of spherical SiO₂ prepared by modified Stöber method is about 200 nm and it has good dispersibility. When the content of SiO₂ is about 75% (mass fraction) in SiO₂/g-C₃N₄ composite powder, the specific surface area of composite powder is the largest, about 23.7 m²/g. At the same time, the photocatalytic properties of SiO₂/g-C₃N₄ composite powders with different g-C₃N₄ loading content were investigated under visible light irradiation with Rhodamine B and methylene blue as the target pollutants. Results indicate that with the decrease of the content of g-C₃N₄ in the composite powders, the visible light activity of the composite powder increases gradually. The composite powder with about 25% (mass fraction) g-C₃N₄ has the best photocatalytic degradation effect on Rhodamine B and methylene blue. The reason is that the strong absorption of composite powders enhances the visible light photocatalytic property.

Key words: silicon dioxide/graphitic carbon nitride composite powder, photocatalysis, Stöber method, absorption