Investigation Of Fabrication, Characterization And Property Of Fuctional Titanium Dioxide Nanoporous Materials

It is well known that nanostructured titanium dioxide (TiO₂) has been shown as potential applications in dye-sensitized solar cells, photocatalysis, solar hydrogen generation and gas-sensors. TiO₂ nanoporous materials have attracted considerable attention due to its large surface to volume ratio, high surface activity and high sensitivity. Thus the systematical studies on the preparation and application of nanoporous TiO₂ materials have both scientific and engineering significances.The main results of this paper are summarized as follows:(1) Nanoporous TiO₂ films were prepared on fluorine-doped tin oxide (FTO) conducting glass in NH4F/ethylene glycol electrolyte by electrochemical anodization of pure titanium films deposited by radio frequency magnetron sputtering (RFMS) at room temperature.The influences of anodizing potential, electrolyte composition, and pH value on the surface morphology and photoelectric conversion performance of nanoporous TiO₂ films were extensively studied. The results showed that nanoporous TiO₂ films with high porosity, high surface areas and three-dimensional (3D) networks were observed at 30 V, when the NH4F concentration in ethylene glycol solution was 0.5 wt% and the pH value was 5.0, and exhibit a higher photoelectric conversion efficiency compared with the samples that were prepared with other anodized conditions.(2) Nanoporous TiO₂ films on Ti substrates were grown by an electrochemical anodization in NH4F/ethylene glycol solution at a constant potential. Using two-step anodized preparation procedure to improve the surface morphology, and the performance was modified by doping Fe³⁺. The influences of surface morphology and doping modification on the photocatalytic activity of nanoporous TiO₂ films have been investigated. The results showed that the nanoporous TiO₂ films obtained by the two-step anodizing with an order structure that the diameter of pores and distances between them are uniform, and the as-prepared sample had a high photocatalytic activity and the photo-degradation of methyl orange could reach 52.02% after 150 minutes light irradiation. In addition, the Fe³⁺-doped TiO₂ nanoporous TiO₂ films exhibit a higher photocatalytic activity than the pure TiO₂ nanoporous TiO₂ films due to the the effective separation and transmission of photogenerated electron-hole upon the substitutional introduction of Fe³⁺ into the TiO₂ structure, and the photo-degradation of methyl orange could reach 60.02% after 150 minutes light irradiation.(3) Gd³⁺-doped mesoporous TiO₂ (M-TiO₂) photocatalysts were synthesised using the novel homogeneous precipitation-assisted template method using Ti(OC4H9)4 as the titanium source, multi-walled carbon nano-tubes, urea and soluble starch as the template, dispersant, and inhibitor, respectively. The as-prepared M-TiO₂ samples showed markedly high surface areas and large exposed mesoporous surfaces with different pore sizes ranging from 10.8 to 15.6 nm. Their XRD patterns showed that the addition of Gd had no effect on the crystal phase of TiO₂ in M-TiO₂. Gd³⁺-doping of M-TiO₂ can increase their optical absorption and enhance their photocatalytic property. The results of analysis of the photocatalytic performance of M-TiO₂ showed that 0.12 mol% Gd³⁺-doping can significantly enhance the photo-catalytic activity of M-TiO₂; moreover, the rate of MO photodegradation could reach 97.3% after 150 minutes light irradiation.