Defective black Ti3+ self-doped TiO2 and reduced graphene oxide composite nanoparticles for boosting visible-light driven photocatalytic and photoelectrochemical activity

We present a facile and environmentally friendly way to successfully build partially reduced titanium dioxide nanoparticles integrated with reduced graphene oxide composite nanosheets (RGO/TiO2-x) through an environmental solvothermal method at relatively low temperature. The Ti3+ self-doping of TiO2-x is conducive to enhance its visible light absorption, and the existence of RGO as the electron receiver makes the electrons on TiO2-x transport better to its surface, effectively promoting the separation of electrons and holes. Experiments on photocatalytic degradation of methylene blue dye and phenol colorless organic pollutant by visible light demonstrate that the RGO/TiO2-x assemblies exhibit the highest photocatalytic activity, and that methylene blue solution concentration of used in the experiment is 40 mg L-1, which was more higher than the concentration (10 mg L-1) used in many of reported articles. Compared to the pure TiO2 and TiO2-x, the photodegradation efficiency of methylene blue and phenol can be increased to 100% within 120 min and 150 min under visible light. Moreover, the mineralization rates of MB, such as the total organic carbon (TOC) degradation rate, can reach to 75.7%, 86.6% and 89.4% for m-RGO/TiO2-x, respectively. And the reaction efficiency of RGO/TiO2-x is basically not much changed after 4th cycles, suggesting its excellent photocatalytic stability.