| It is well known that there is still some limitation in the practical application of TiO2 photocatalyst. First, the material only absorbs the light with wavelength shorter than 380nm due to its wide band gap (3.2eV). Second, nano-TiO2 powders get aggregated easily during the photocatalytic process resulting in decrease of degrading efficiency, and also is hard to separate from the reaction system for recycle. Third, the low quantum efficiency, i.e., photo-generated carriers easily get into recombination, also weakens its photo-catalytic activity. Therefore, it is imperative to resolve above problems to improve the performances of TiO2 based photocatalysts.Because of the good conductivity, rough surface and adsorption ability, carbon paper (CP) electrode was used as a substrate to load nano-TiO2 photocatalyst in this research. While it was convenient for recycle use of as prepared composite electrode, an external voltage was also easily applied at the electrode to promote the separation of photo-generated carries which is beneficial to the catalytic reaction. In the meantime, the visible light activity of the photocatalyst was also improverd via C element dopping. The main achievements are as following:1. Nano-TiO2 rod array with rod height ranging from 5? m to 7?m was fabricated on CP surface by hydrothermal reaction at 180?. At the same time, appropriate amount of glucose was added into hydrothermal solution to obtain C-doped TiO2/CP electrodes, of which C-TiO2/C-2 has Uv-Vis absorption up to 428nm that is favourable to improve visible light response of the photocatalyst. More glucose in hydrothermal solution formed carbon film and microspheres on the top of TiO2 rods, which hampered the absorption of light. The isoelectric point of the composite electrode was about 5.4-5.5, and it is possible to optimize photocatalytic activity through adjusting initial pH of reaction solution and applied bias at the electrode that change the adsorption of pollutants at catalyst surface. Vertically oriented TiO2 nanorods were also favorable to the moving of photo-excited electrons to underlying CP electrode under external bias.2. The photocatalytic performances of C-TiO2/C-2 on methyl orange (MO:5mg.L-1), methylene blue (MB:4mg.L-1), Cr(?) (2 mg.L-1) and the mixture of MO or MLB with Cr(?) were investigated under condiction of different initial pH and applied bias. It was found that acidic solution was benefical for the degradation of MO and Cr(?), while more basic solution was favorable to MLB. Without external bias, the degradation rate of each pollutant in mixture solution of MO and Cr(?) was lower at pH=4 than the value in corresponding single-component solution, that indicated a competitive inhibition between MO and Cr(?). In contrast, MLB and Cr(?) presented higher degradation rate in their mixture solution and showed a cooperative degradation. Upon external bias was applied, the degradation rate of MO or Cr(?) was increased with increasing bias. However, the degradation rate of MLB increased firstly and then decreased with increasing bias. For mixed solution of Cr(?) with MO or MLB,the degradation rate of each pollutant at the bias of 400mV was always higher than the value found in its pure solution without applying bias. |
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