Enhanced photocatalytic activity of a TiO₂/graphene composite by improving the reduction degree of graphene

Two kinds of graphene prepared by a high-temperature exfoliation and a solvothermal method were used as supports of a TiO₂ catalyst (P25) from Degussa, Inc to prepare TiO₂/graphene composites. The photocatalytic activities of the composites were evaluated by their degradation of Rhodamine B in aqueous solutions under visible light. Results indicate that the composites prepared by high-temperature exfoliation have much higher photocatalytic activities than those produced by the solvothermal method or the unsupported P25. Both the adsorption capacity of Rhodamine B on the composites and their light absorption characteristics are independent of the kind of graphene used. The activity increases with exfoliation temperature and reduction degree of the graphene regardless of the methods and conditions used, indicating that a high degree of reduction of graphene can inhibit the recombination of electron-hole pairs generated by light irradiation by increasing electron transfer from TiO₂ to the graphene layer.