▎ 摘　　要

A transparent TiO2-C@TiO2-graphene free-standing film has been synthesized by electrostatical self-assembling GO nanosheets on a cellulose-TiO2@TiO2 film prepared by a one-step hydrothermal method followed by thermal annealing at 500 degrees C. Scanning and transmission electron microscope observations have shown graphene wrapped flower-like micro/nanostructure TiO2 particles uniformly distribute on TiO2-C fibers that are interconnected with each other to form a 3D reticulate microstructure. X-ray photoelectron spectra have demonstrated that interaction between the TiO2 and graphene facilitates the generation of O-Ti3+ species and Ti-O-C bonds. As a result, the TiO2-C@TiO2-graphene film exhibits a significant enhancement of light absorption within the visible region as compared to the TiO2-C@TiO2 film. Meanwhile, the introduction of a graphene layer slows the recombination of photogenerated electron-hole pairs, increasing the charge transfer rate of electrons. Thus, in the photocatalytic degradation reaction of methylene blue, the photodegradation rate constant for the TiO2-C@TiO2-graphene film is 2.2 times higher than that of the TiO2-C@TiO2 film obtained from thermal treatment of the cellulose-TiO2@TiO2 film. The enhanced photocatalytic property is well consistent with the photoelectrical responses, electrochemical impedance spectroscopy analyses and photoluminescence spectra results. This work may provide a rational and convenient strategy to construct transparent free-standing films with visible light photocatalysis toward environmental purification.