Enhanced Photocatalytic Activity and Electron Transfer Mechanisms of Graphene/TiO2 with Exposed {001} Facets

We present a simple and feasible strategy to synthesize the novel anatase TiO2/graphene composites with exposed TiO2 {001} high-energy facets by the hydrofluoric acid and methanol joint assisted solvothermal reactions. During the synthesis process, graphene was uniformly covered with a large number of anatase TiO2 nanoparticles (20-25 nm), exposing the {001} facets. The X-ray photoelectron spectroscopy and X-ray absorption measurements show the presence of electron transfer between TiO2 and graphene. Furthermore, transient photovoltage spectra of the composite also exhibits prolonged mean lifetime of electron-hole pairs compared with pure TiO2. The electron transfer between Ti and C will greatly retard the recombination of photoinduced charge carriers and prolong electron lifetime, which contribute to the enhancement of photocatalytic performance. During the photocatalysis measurement, the TiO2/graphene composites have high photocatalytic activity compared with the P25 under UV light, likely due to the effective separation of photoinduced charge and exposure of high reactive {001} facets.