Enhanced sunlight photocatalytic activity and recycled Ag–N co-doped TiO2 supported by expanded graphite C/C composites for degradation of organic pollutants

Abstract

Removing organic pollutants from wastewater is urgent for developing a sustainable ecological environment. A highly efficient visible light photocatalyst was synthesized through a sol–gel method using C/C composites (expanded graphite dipping in the phenol formaldehyde resin, EGC) coated with Ag, N co-doped TiO2. The as-prepared composites were characterized through scanning electron microscopy (SEM), X-ray diffraction (XRD), N2 adsorption–desorption (BET), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible light diffuse reflectance spectroscopy (UV–Vis-DRS). The XRD and N2 adsorption–desorption (BET) results revealed that the photocatalysts were composed of mesoporous structures mainly with anatase TiO2. The effects of Ag content and calcination temperature on the photocatalytic activity of Ag–N-TiO2/EGC photocatalysts were studied. The results showed that under visible light, the photocatalytic efficiencies of Ag1.0-N-TiO2/EGC (550 °C) obtained for the degradation of Rhodamine B (RB) and diesel are 7.4 times and 3.9 times higher, respectively, than those of N-TiO2/EGC with high mineralization. The enhanced photocatalytic activity of the Ag–N-TiO2/EGC composites was attributed to the porosity and flexible electron transport paths for formation of superoxide radicals. These characteristics assured Ag–N-TiO2/EGC photocatalyst as a high-efficiency photocatalytic material for organic pollutant degradation under visible light.