| As one of the most famous and widely used semiconductors, TiO2 owns certain outstanding advantages, such as non-toxic, stable and low-cost, etc. However, its efficiency of utilizing solar energy is heavily limited due to the restricted absorbance of visible light. In this thesis, Cu2O with narrower band gap was used as a sensitizing semiconductor to couple with TiO2 to form Cu2O/TiO2 heterostructure, which exhibited highly enhanced photocatalytic efficiency (PE) both under UV and visible light irradiation. The photocorrosion of Cu2O and the factors that affect the activity of the heterostructures were studied, and the band structure at the interface of the Cu2O/TiO2 heterostructure was also characterized by"in situ"X-ray photoelectronic spectra (XPS).Cu2O particles with different morphologies and sizes were successfully prepared by wet chemical method. It was found that the Cu2O particles with different morphologies owned highly selective adsorption of anionic dyes due to electrostatic adsorption. While the Cu2O particles with different sizes were found to exhibit different stabilities during the photocatalytic process. The results suggested that Cu2O nanoparticles were easy to be photo-oxidized to CuO by photo-induced holes since Cu1+ existed on the surface. Comparatively, Cu2O micro-particles were more stable in photocatlaytic process due to existing Cu2+ on the surface. It was also suggested that the addition of hole scavenger (eg. methanol) in the pollutant solution could restrain the photocorrosion of Cu2O nanoparticles and promote the PE meanwhile.Cu2O/TiO2 hybrid and Cu2O/TiO2 nano-nano heterostructures were successfully prepared by physical milling and chemical precipitation method, respectively; the factors that affect PE were studied and summarized as follows. Firstly, the interfaces between the two semiconductors were very important to the heterostructure, Cu2O/TiO2 nano-nano heterostructure composed of Cu2O nanoparticles (~3nm) and P25(commercial TiO2, 20~30nm ) had much better PE than that of Cu2O/TiO2 hybrid due to higher contact area between the two semiconductors. Secondly, the content of Cu2O had extraordinary influence on PE of Cu2O/TiO2 nano-nano heterostructure (or hybrid), less Cu2O content was better in UV-visible light, while higher Cu2O content was better in visible light; the heterostructures with Cu2O contents of 30wt.% and 70wt.% possessed of the highest photocatalytic activities under UV-vis light and visible light irradiation, which were almost 5 times and 26 times higher than that of P25, respectively. Cu2O/TiO2 nanotube (TNT) arrays heterostructures were successfully prepared controllably by electrochemical precipitation, and the preparing conditions influencing on the precipitation process were studied. Four different types of Cu2O could be obtained by adjusting the pretreatment conditions of TNT arrays, the reduction potentials and the electrolyte conditions. The results indicated that the growth of Cu2O was controlled by kinetics, octahedral Cu2O just can be obtained at the current density higher than 0.09mA/cm2. Depositing crystallized Cu2O nanoparticles and octahedral particles into TiO2 nanotube structures favored the promoting of PE. Eespecially, Cu2O octahedral particles had significant photocatalytic and adsorptive activities due to the exposure of {111} facets; whereas, amorphous Cu2O decreased PE of the heterostructure.Thin Cu2O layers were successively deposited on rutile TiO2 (001) single crystal surfaces that had different levels of defect concentrations to form Cu2O/TiO2 heterojunctions, and the resultant band bending and offset characteristics were studied by"in situ"X-ray photoelectron spectroscopy (XPS). It was found that the concentrations of defects could be controlled by the oxidizing temperature. Oxygen vacancies and interstitial Ti3+ defects co-existed in the 350℃treated surface, while near TiO2 stoichiometry surface was obtained at the temperature of 600℃. The defect concentrations were found very important to the oxidization process of Cu on the TiO2 surface. The higher the defect concentration was, the easier the oxidization of Cu was. Cu2O was found to disproportionately decompose to CuO and Cu on the 350℃treated surface. Furthermore, the presence of the defects in TiO2 surface dramatically influenced on the band bending and band offset at the interface; the less defects in TiO2 substrate was, the larger band bending values on the TiO2 side were observed, inducing smaller conduction band offset. This conclusion will help to design more effective Cu2O/TiO2 heterojunctions for solar energy conversion.
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