Materials Characteristics, Photodegradation and Electrical Properties of CuOx/TiO2 Composite Photocatalysts
| Autor: | Bo-Kai Chao, 趙柏凱 |
|---|---|
| Rok vydání: | 2009 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 97 CuOx/TiO2 composite photocatalysts with different CuOx dopant concentrations were prepared by Cu(hfac)2•2H2O as a precursor via incipient wetness impregnation method. Due to the combination of p-type CuOx and n-type TiO2, p-n junction rigion were formed at the interface of CuOx and TiO2 particles. The formation of the p-n junction could reduce the recombination of electrons and holes, and enhance the photocatalysis activity. In this study, crystal structure, surface morphology, chemical properities, and optical properities of CuOx/TiO2 photocatalysts were investigated. According to the XRD analysis, the doping of the CuOx did not change the microstructure and surface morphology of TiO2, indicating that CuOx particles were adhered onto TiO2 surface. In the chemical analysis(XPS, Raman), the type of CuOx were CuO, Cu2O, and Cu(OH)x, revealing that Cu atom in Cu(hfac)2•2H2O precursor could combine with the hydroxyl radical on the surface of TiO2 to form the Cu(OH)x. In the optical properties, the absorption edge of CuOx/TiO2 composite photocatalysts were extended to longer wavelengths, and the doping of CuOx were successfully decreased the recombination of electrons and holes from PL analysis. In photodegradation test, Methylene Blue and K2Cr2O7 were used as the pollutants for the photo-oxidation and photo-reduction processes, respectivity. For photo-oxidation of Methylene Blue, the reaction rate constants of 1%-CuOx/TiO2 photocatalysts prepared at various temperatures were between 1.9 ×10-3 and 2.3 ×10-3 min-1 under the fluorescent lamp, which are greater than that of P25 (1.4 ×10-3 min-1), and the photodrgradation efficiency of 1%-CuOx/TiO2 composite photocatalysts were between 39.4 % and 46.1 %, were also greater than P25 (30.7 %). Under the BLED lamp, the reaction rate constants and the photodrgradation efficiency of 1%-CuOx/TiO2 photocatalysts were also higher than P25. However, at heavy CuOx doping concentration, excessive CuOx increased the formation of the Cu(OH)x, which could cover the surface of TiO2, and leaded to decrease on the photocatalytic activity of photocatalysts. In the photo-reduction process, the optimum parameter in this study was 1%-CuOx/TiO2 calcined at 300℃.Under fluorescent lamp, the reaction rate constants was 2.3×10-3 min-1，greater than that of P25 (1.0×10-3 min-1). For Dye-Sensitized Solar Cells (DSSC) application, the doping of CuOx decreased the efficiency of DSSC. The reason for the lower efficiency could be due to the recombination of electrons from dye and holes from CuOx. As CuOx is p-type semiconductor with a narrow energy band gap, pairs of electrons and holes could be easily produced under irrdation of solar simulator. Electrons injected from the excited dye molecules could recombined with the holes from CuOx. Therefore, generated electrons from dye could not quickly transfer through TiO2 layer to reach the ITO substrates for the further redox reaction of electrolyte. This result indicated that CuOx/TiO2 composite electrodes were not suitable for DSSC use. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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