Immobilized Nanometer Tio <sub> 2 </ Sub>-situ Preparation And Photocatalytic Properties

In this thesis, micro-arc oxidation(MAO) technique was taken to prepare porous and uniform TiO₂ film on the surface of pure Ti plate. Na3PO4 ?12H2O was selected as the electrolyte. Electrolyte concentration, oxidation time and current density affected the phase composition, morphology and H₂ production rate of TiO₂ film. The three parameters were investigated to produce TiO₂ film of good H2 production performance. Furthermore, transitional metal ions(Ni, Co, Cr) and nonmetal elements(S,C) were doped to extend the absorption edge of TiO₂ into the visible region. The structure and physicochemical properties were characterized by X-ray diffraction (XRD), UV-Vis, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy(XPS).The main phase composition of the TiO₂ film is anatase phase under the condition of growing in the electrolyte of Na3PO4 ?12H2O. The transformation of anatase phase to rutile phase is caused by high temperature or by high applied voltages. The surface morphology of TiO₂ film is closely related to the conditions of the MAO process. The surface was rough and inhomogeneous when the applied voltages are too high or too low. Pores dispersed on the surface are well connected in the inner part of TiO₂ films. The size of pores is in the range of 1–2μm. H2 production rate of TiO₂ film reached the maximum value of 2.84μmol/ cm²Â·h when the electrolyte concentration is 0.11 mol/L, the oxidation time is 9 min, the current density is 4 A/dm².Furthermore, nonmetal elements(S, C) were doped to extend the absorption edge of TiO₂ into the visible region. Na₂SO₃ and Na₂S2O₃ were used as the S source, respectively. The experimental result showed that the crystalline of TiO₂ had no obvious changes, the absorption edge of TiO₂ had a shift toward long wavelength is observed in the UV–Vis absorption spectra with increasing the concentration of Na₂SO₃ or Na₂S2O₃ in the electrolyte. H2 production rate of TiO₂ film reached the value of 0.279 μmol/cm²?h when the concentration of Na₂SO₃ is 0.03 mol/L, and 0.284μmol/cm²?h when the concentration of Na₂S2O₃ is 0.01 mol/L. However, the film corrosion could be happened when the amount of S ions in the electrolyte exceeded a certain concentration.The crystalline of TiO₂ was affected by doping transitional metal ions (Ni²⁺, Co²⁺, Cr³⁺), the peak of 2θ=25.281°was gradually degenerated with the increment of concentration of transitional metal ions. Moreover, the color of TiO₂ film changed with doping different transitional metal ions. The H2 production rate reached the maximum value of 0.378μmol/ cm²Â·h under Doping Cr³⁺.