In Situ Growth of TiO2 in Interlayers of Expanded Graphite for the Fabrication of TiO2-Graphene with Enhanced Photocatalytic Activity

We present a facile route for the preparation of TiO2-graphene composites by in situ growth of TiO2 in the interlayer of inexpensive expanded graphite (EG) under solvothermal conditions. A vacuum-assisted technique combined with the use of a surfactant (cetyltrimethylammonium bromide) plays a key role in the fabrication of such composites. Firstly, the vacuum environment promotes full infusion of the initial solution containing Ti(OBu)(4) and the surfactant into the interlayers of EG. Subsequently, numerous TiO2 nanoparticles uniformly grow in situ in the interlayers with the help of the surfactant, which facilitates the exfoliation of EG under the solvothermal conditions in ethanol, eventually forming TiO2-graphene composites. The as-prepared samples have been characterized by Raman and FTIR spectroscopies, SEM, TEM, AFM, and thermogravimetic analysis. It is shown that a large number of TiO2 nanoparticles homogeneously cover the surface of high-quality graphene sheets. The graphene exhibits a multi-layered structure (5-7 layers). Notably, the TiO2-graphene composite (only 30 wt% of which is TiO2) synthesized by subsequent thermal treatment at high temperature under nitrogen shows high photocatalytic activity in the degradation of phenol under visible and UV lights in comparison with bare Degussa P25. The enhanced photocatalytic performance is attributed to increased charge separation, improved light absorbance and light absorption width, and high adsorptivity for pollutants.