Studies On Fabrication Of Composite Titania Nanotubes Arrays And Application In Photoelectrocatalysis

TiO₂ nanotube (NT) arrays prepared by anodization have attracted increased attention due to the large surface area, size tunable property, high orientation as well as the stable physical/chemical properties. TiO₂ NT semiconductors contain much more free spaces in their interior that can be filled with active materials such as chemical compounds, magnetic particles and noble metals, giving them enhanced photovoltaic, electromagnetic and catalystic characters. The unique properties make TiO₂ NT arrays have wide applications in various fields such as solar energy storage and utilization, photovoltaic conversion, chemical and biosensor, photochromic and photocatalytic (photoelectrocatalytic) degrading contaminants in atmosphere and water.However, TiO₂ has high band gap energy (3.2 eV), which limits its wide application in visible light range of solar spectrum. Therefore, Fe₂O₃ and CuO were modified on TiO₂ NT arrays to extend the absorption spectra into the visible light region in this work. And the photocatalytic properties of Fe₂O₃, CuO modified TiO₂ NT arrays were investigated. The detail is listed as below:(1) Fabrication, characterization and photoelectrochemical properties of Fe₂O₃/TiO₂ NT arrays: The anodic TiO₂ NTs with 90 nm pore size, 320 nm length were loaded with Fe(OH)₃ by chemical deposition. After calcination in oxygen, Fe₂O₃/TiO₂ NT arrays were obtained. Compared with the unmodified TiO₂ NTs, the introduction of Fe₂O₃ results in the zero-current potential negatively shift from -0.36 to -0.78 V. The maximum photocurrent is obtained on Fe₂O₃/TiO₂ NT arrays with 0.5 at% Fe content, which is 7 times that achieved on unmodified TiO₂ NTs.(2) Fabrication, characterization and application of CuO/TiO₂ NT arrays: Cu was electrodeposited on the anodic TiO₂ NT arrays by chronoamperometry, which content was controlled by tuning the electrodepositing duration. Then, Cu/TiO₂ NTs were anodized in NaOH solution to obtain CuO/TiO₂ NTs. Photoelectrocatalytic degradation of 4-chlorophenol was successfully achieved on CuO/TiO₂ NTs.(3) Investigation of photoelectrodegrading pentachlorophenol (PCP) on CuO/TiO₂ NT arrays: Externally applied potential and concentration of the supporting electrolyte (Na₂SO₄) are the key factors to affect the degrading rate of PCP on CuO/TiO₂ NTs, which optimum values are 0.6 V and 0.1 M, respectively. 80 mL 10 mg/L PCP was degraded completely in 2 h under the simulated solar light. Furthermore, co-detoxicity of Cr(VI) and PCP was also achieved on CuO/TiO₂ NT arrays. The high catalytic activity of the co-existing system can be attributed to the synergetic effect of Cr(VI) consuming the photo-generated electrons and PCP depleting the holes.