Preparation Of TiO₂-Reduced Graphene Oxide Nanocomposites With Highly Enhanced Photocatalytic Activities

Since the photocatalytic properties of semiconductors have been discovered,titanium dioxide(TiO2)nanoparticles have drawn extensive attention because of their extraordinary properties such as inherent electric,optical,and catalytic properties,easy availability,nontoxicity,and long-term stability.Particularly,the prominent photocatalytic performance of TiO2 leads to a variety of promising applications.However,photogenerated electron-hole recombination and the wide bandgap energy significantly restrict the catalytic efficiency of TiO2.Various approaches have been developed to overcome this problem,yet it remains challenging.Recently,graphene modification of TiO2 has been considered as an effective alternative to enhance the photocatalytic performance of TiO2.This thesis mainly focuses on the TiO2-Reduced Graphene Oxide(RGO)nanocomposites,including the following parts:Firstly,TiO2-RGO and TiO2 hollow shell-RGO binary nanocomposites were prepared by an efficient but simple hydrothermal method.Au-TiO2-RGO nanocomposites were also synthesized by a hydrothermal method based on the binary materials.Secondly,the prepared nanocomposites were characterized by several advanced techniques such as X-Ray Diffraction(XRD),Scanning Electron Microscope(SEM),Transmission Electron Microscope(TEM),UV-vis spectroscopy,etc.Thirdly,the photocatalytic activities of the synthesized nanocomposites were evaluated by degrading the organic molecules(methylene blue,MB)under ultraviolet light and simulated sunlight.Based on the experimental research,the conclusions of this thesis can be summarized as below:(1)The well-formed TiO2-RGO nanocomposites were successfully synthesized via a one-step hydrothermal method and the optimum hydrothermal reaction conditions were 180?,8 h.The photocatalytic results showed that the prepared TiO2-RGO nanocomposites with different RGO contents exhibited enhanced photocatalytic activities,and the optical RGO content was determined to be 1 wt%.Under ultraviolet light,the photocatalytic degradation rate constant(0.537 min-1)was?4.5 times than that of pure TiO2(0.120 min-1).(2)TiO2 hollow shell was prepared by a sol-gel method,and then it was combined with GO to synthesize TiO2 hollow shell-RGO nanocomposites by a hydrothermal method.The nanocomposites showed an obvious blue shift.Compared with TiO2-RGO nanocomposites,the photocatalytic performance of TiO2 hollow shell-RGO nanocomposites was obviously enhanced under ultraviolet light.(3)Uniform Au nanoparticles(?14 nm)prepared successfully by a classical seed method were combined with TiO2 and RGO to prepare Au-TiO2-RGO nanocomposites by a hydrothermal method.Under simulated sunlight,the synthesized nanocomposites showed enhanced photocatalytic performance,and the optimum Au nanoparticles content was determined to be 1%.The degradation rate constant(0.018 min-1)was-2 times than that of pure TiO2(0.009 min-1).