| Semiconductor photocatalysis is one strong technique to solve the increasingly serious environmental pollution problems. Of all the semiconductor photocatalysts, titanium dioxide (TiO2) has been intensively investigated in photocatalysis due to its relatively high stability, low cost, non-toxicity and high photocatalytic efficiency. But the applications of TiO2photocatalyst are greatly restricted by its low quantum efficiency and wide band gap, which result in its high recombination of photo-generated electron-hole pairs and ineffective utilization of visible light, respectively. In the past decades, lots of effective approaches have been developed to further modify the TiO2structures and properties to increase the lifetime of photo-generated electron-hole pairs and narrow the band gap. Among all the effective methods, combining TiO2with carbonaceous materials is an interesting way to increase photocatalytic activity via the synergistic effect between carbon and TiO2. The main contents of our works are as the followings.(1) The carbon/TiO2nanocomposites were fabricated by a simple one-step carbonization method with different polymers as precursors, and the carbon was generated by carbonizing polymers at high temperature. Due to the dehydration carbonation effect of polymers, carbon was formed in and out of the TiO2nanoparticles. Raman spectra show that the states of carbon in the composites are different because of the difference of polymers. The photo-degradation study of rhodamine B was carried out under UV-Vis light irradiation, and the results show that the photocatalytic activities of carbon/TiO2nanocomposites are affected severely by the states of carbon during the formation process, including dopants and the regulation role to the oxygen vacancies.(2) The carbon/Ti02nanocomposite was prepared by a simple hydrothermal process. And the content of carbon on the surface of the composite was adjusted through etching in air at high temperature. The characterization results of the synthesized nanocomposites indicate that this nanocomposite, an average size of50nm, is composed of well-defined crystallized TiO2and the amorphous carbon either on the surface or among the particles. The TiO2in the composite are the mixed phase system of anatase and rutile. Measurement result of the photocatalytic degradation of rhodamine B shows the photocatalytic activity of nanocomposites, especially annealed at400℃, are higher than that of the pure TiO2. It indicates that the carbon enhances the photocatalytic activity of nanocomposites by the synergistic effect between TiO2and carbon, such as retarding the recombination of photo-generated electron-hole pairs, improving the adsorption and absorbing more light.(3) A unique TiO2/carbon@TiO2core-shell nanocomposite was fabricated by a two-step hydrothermal method. High-resolution transmission electron microscopy images show the size of the nanocomposites is about50-100nm, which are composed of well-defined crystallized titania on the shell with the TiO2/carbon composite as core. The existence of the amorphous carbon in the core can be proved by Raman spectra and thermogravimetric analysis. X-ray diffraction patterns and Raman spectra show that the crystalline of TiO2is improved after the second hydrothermal treatment and the TiO2are the pure anatase phase. Measurements of the photocatalytic degradation of rhodamine B show that the photocatalytic activity of Ti02/carbon@Ti02core-shell nanocomposite is higher than that of the initial TiO2core and pure TiO2because TiO2on the shell has high crystallinity and high content of surface oxygen vacancies (SOVs) after the second hydrothermal treatment. Moreover, the synergistic catalytic effect of the carbon in the core can also enhance the photocatalytic activity of the nanocomposite, such as retarding the recombination of photo-generated electron-hole pairs and absorbing more light. |
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