Mechanism of UV-assisted TiO2/reduced graphene oxide composites with variable photodegradation of methyl orange

Abstract

TiO₂/reduced graphene oxide (TiO₂/rGO) composites with variable photodegradation efficiency of methyl orange (MO) were synthesized by combining TiO₂ and graphene oxide (GO) under ultraviolet (UV) irradiation. In this study, the influences of TiO₂ content and UV irradiation time on the reduction degree of GO during fabrication of the TiO₂/rGO composite were investigated and characterized by X-ray diffraction (XRD), Raman spectrum, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The experimental results showed that the maximum reduction degree of GO can be achieved by controlling the weight ratio (TiO₂/GO) of 10 under 15 min UV irradiation, and the corresponding composite showed 1.71 times the higher photodegradation efficiency of MO over pure TiO₂, which results from the newly generated rGO with high electrical conductivity that decreases the recombination rate of excited electrons–holes in TiO₂. The results also demonstrated that the photodegradation efficiency of the TiO₂/rGO composite was closely related to the reduction of GO during fabrication of the composite. The more UV irradiation during fabrication of the composite, the higher reduction degree of GO, and therefore higher photodegradation efficiency of the TiO₂/rGO composite can be achieved, but excessive UV irradiation plays a negative effect on the photodegradation efficiency of the composite. Finally, the mechanism of UV-assisted TiO₂/rGO composites with variable photodegradation efficiency was proposed in terms of the reduction degree of GO.