Preparation, Modification Of Tio₂ Based Nanotubes And Studies Of Their Properties

The energy and environment issue have presented a variety of challenge for us. Energy problem is the key problem. Currently, transforming the solar energy into electrical energy and producing hydrogen using the solar energy are the two promising research interest. Developing high efficiency photoelectrode with low cost is very important. The anodic TiO₂ nanotube arrays posse good and uniform microstructure, bigger specific surface area and stronger adsorption ability. Thus, it showed evident superiority in the solar energy application aspect.However, TiO₂ can just absorb the ultraviolet light (UV) with a wavelength of 400 nm or less at room temperature due to its broad band gap. Since UV light is only 3-5% part of the solar spectrum, the photocatalytic activity of TiO₂ cannot be sufficiently activated under solar light irradiation, which strongly limits the use of solar spectra as a source for photodecomposition of pollutant. Therefore, the extension of the photoactive wavelength region of TiO₂ into the visible region and improvement of quantum efficiency are desirable for popularizing more TiO₂ photocatalyst.For this purpose, the anodic TiO₂ nanotubes have been modified by various ways to obtain visible light reactivity, such as impurity doping, inorganic compound and dye sensitization. In addition, the anodized TiO₂ nanotubes can be used for the template to synthesize other functional material for its unique structure. Focusing on these problems, we mainly developed the work as following:(1) TiO₂ nanotube arrays with controllable topography were prepared by the anodization method. The growth of the nanotubes in glycerol based electrolyte or in ethylene glycol based electrolyte were investigated. The effects of the process parameters on the TiO₂ Nanotubes growth were systemically studied, such as the electrolyte concentration, oxidation voltage and oxidation time. By XRD, FESEM, HRTEM, UV-vis adsorption spectra, the nanotubes microstructure, phase and crystal structure were examined. The results showed that the nanotubes prepared in the glycerol based electrolytes posse the specific"bamboo type"feature, and the size of the"bamboo joint"as well as the distance of the adjacent"bamboo joint"are influenced by the oxidation voltage. With the increasing of the oxidation voltage, the"bamboo joint"of the nanotubes become smaller and the distance of the adjacent"bamboo joint"become bigger. This is probably due to that the high voltage generates a strong electric field, and the"bamboo joint"was dissolved under the electric field. While the nanotubes prepared in the ethylene glycol based electrolyte do not posse the"bamboo-type"feature, and the wall of the nanotubes is smooth and straight. By investigation of the process parameters, we found the oxidation voltage and oxidation time affect the length and the diameter much when other process parameters are fixed. By adjusting the process parameter, the nanowires and the nanotubes coexist. The growth process was investigated and the length of the anodic TiO₂ nanotubes was controlled by the dissolve-formation process. When the electrochemical corrosion rate of the nanotubes bottom is equal to the dissolve rate of the nanotubes top, the nanotubes length does not change any more.(2) The TiO₂ nanotubes were loaded with Cr₂O₃ by the dipping method. The dipping time was investigated. The enhancement of the photoelectrochemical property under visible light irradiation was analysed by the UV-vis absorption spectra and linear sweep voltammograms.(3) By a facile method, a new kind of meso-unsubstituted porphyrins bearingβ-substituents porphyrin was synthesized. This method, which relies on the construction of a bis-iodoβ-functionalized porphyrin precursor and its subsequent elaboration, was used to prepare the bisbithiophene substituted porphyrin. Compared to the most effective sensitizer, the commercial N719 dye, this new porphyrin was shown to act as an efficient sensitizer for use in DSSCs. Although the efficiency of the porphyrin is slower than that of the N719, it showed a promising future because of its low cost and facile synthesis method.(4) Whether the SECM technique can be used to screen the sensitizers was investigated by combining a CH Instruments dispenser and the SECM. The results of the photocurrents generated by arrays and bulk film are comparable. The study serves to highlight the utility of a modified SECM-based technique, which permits a rapid, initial evaluation of photosensitizers for use in DSSC applications. This SECM technique is attractive in that it should not only permit the facile identification of individual new dyes but also permit the potential synergetic effects of multiple dyes to be easily tested. In addition to the latter benefits, the present study serves to underscore the combination of a piezodispenser and SECM as a means of fabricating quickly, easily, and in a reproducible fashion ca.400μm spot-size sensitizer arrays and evaluating their sensitization effects.(5) By combining the anodization method and the hydrothermal synthesis method, we used the TiO₂ nanotubes as the template to synthesize the perovskite functional material. We investigated the influence of the hydrothermal reaction condition on the microstructure of the as-prepared CaTiO₃ and BaTiO₃ material. The usages of the anodic TiO₂ substrate and an alkaline environment are the two crucial keys in ensuring the formation of CaTiO₃. Furthermore, the alkaline concentration is the key factor in determining the resulting CaTiO₃ size and morphology. The rectangular prism-shaped CaTiO₃ structures as well as the calcium reservoir facilitate the growth of apatite.(6) By using a facile electrochemical oxidation process and a simple solution immersion technique, we fabricated a stable, compact and higher adhesive force superhydrophobic films on titania/titanium surface. We tested the corrosion resistance property of the superhydrophobic film using the potentiodynamic polarization curves and the electrochemical impedance spectroscopy. The results indicated the superhydrophobic films have an excellent corrosion resistance property.