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Enhanced the Photoelectrocatalytic Activities of BiVO4and α-Fe2O3and Photoelectrochemical Protection of Cu

Author: LiHaiLi
Tutor: CaoFaHe
School: Zhejiang University
Course: Chemistry
Keywords: Photoelectrocatalysis visible light BiVO4 α-Fe2O3 photoelectroprotection
CLC: O643.3
Type: Master's thesis
Year: 2014
Downloads: 48
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Abstract


With the rapid economic development, the resulting energy shortage becomes a more and more serious prolem for human beings. Therefore, looking for clean and efficient new energy is particularly important. Solar energy is inexhaustible, non-polluting and renewable; hydrogen fuel has high combution value and its combustion products are non-polluting. Thus, solar hydrogen through photocatalytic decomposition of water is one of research hot topic currently.BiVO4and α-Fe2O3, as typical visible light catalysts with low cost and non-toxic, are rather ideal material of photocatalytic decomposition of water. But there are shortcomings such as high recombination of photogenerated electron-hole pairs, slow interfacial charge transfer, and etc. Although a variety of methods have been taken to improve the photoelectric conversion efficiency, but the reported value is still much lower than the theoretical maximum, and also most methods are complicated and/or high cost. In order to improve the performance of photoelectrochemical oxidation water or photoelectrochemical activity over these catalysts, in this thesis, simple and economic electrochemical methods such as electrochemical reduction and electro-deposition are adopted to modify the surface of these materials.In the first part of the thesis, BiVO4electrodes were prepared on indium-conducting (ITO) glass through metal-organic decomposition and then were treated by electrochemical reduction in a standard three-electrode cell. The results show that the photoelectrocatalytic activity of the BiVO4electrode was greatly improved by the pretreatment. To understand the mechanism, the photoelectrodes were characterized by scanning electron microscopy (SEM), X-ray single crystal diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectra, and the interfacial transfer and recombination of photogenerated charge, conductivity of the electrodes were studied by electrochemical impedance spectroscopy (EIS) and Mott-schottky (M-S) relationship. It was demonstrated that the enhanced performance was mainly resulted from an accelerated charge-transfer rate and reduced charge recombination. The employed method is simple, economical and controllable. In the second part, α-Fe2O3and Ti doped α-Fe2O3film electrodes were prepared on ITO glass by sol-gel method, then FeOOH was electrodeposited on their respective surface. The results shows that the photoelectrocatalytic activities of the film electrodes were greatly improved by such a modification. In addition, the electrodes were characterized by SEM, XRD, XPS and Raman spectroscopy. The interfacial transfer and recombination of photogenerated charge, conductivity of the electrodes were examined by EIS and M-S relationship. It is concluded that the improved activity is mainly due to the accelerated charge-transfer rate and reduced charge recombination by FeOOH. This provides a new method for improving the photoactivity of hematite.Metal corrosion causes great losses in people’s daily life. The traditional method of sacrificial anode protection consumes metal continuously and needs to keep compensation for protecting metal from corrosion. The technology of semiconductor photocatalytic is available for metal anticorrosion and has long service life and low cost. It mostly adopts TiO2, which can only use ultraviolet part of sunlight. In the third part, the copper is protected using dye-sensitized TiO2electrode that can make use of visible light. The effect of the system composition on the short-circuit current was studied. The results showed the photoelectrode can protect copper from corrosion using visible light. This provides a new perspective of solar energy utilization and metal anticorrosion.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic
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