The Study On Preparation, Characterization And Photoelectric Properties Of CdSe-TiO₂Nanotube Array Films

With the rapid development of society and economy, environmental pollution and energy crisis become more and more serious. Low-cost photocatalyst materials, which can high efficiently utilize solar energy, are one of promise system to solve these problems. TiO2semiconductor, as a high efficiency, chemically stable photocatalyst with good electronic reception and conduction properties, can effectively utilize solar energy and control environmental pollution. However, TiO2can be activated only by ultraviolet irradiation, which just accounts for4%of the total solar energy, owning to its relatively large band gap (3.2eV for the anatase phase), resulting in its low solar energy utilizing efficiency. In addition, the high recombination of photoinduced electron and hole pairs greatly depresses the quantum efficiency and photocatalytic activity of TiO2, affecting the application of this material in practical application.In this paper, the visible light absorption and charge separation efficiency of TiO2are improved by preparing the tubular structure of TiO2nanotube arrays and constracting TiO2-based heterojunction structure with a narrow band gap semiconductor, CdSe. On the one hand, the unique nanastructure can facilitate separaion of photoexcited charages and results in higher charge collection efficilitates; On the other hand, the heterojunction can not only extend the absorption wavelength range to visible light region but also inhibit the recombination of photo-generated electron-hole pairs, and thus improve the photocatalytic efficiency of TiO2.Firstly, TiO2nanotube arrays were prepared by anodic oxidation method. Then small CdSe nanoparticles were deposited into TiO2nanotube arrays via the cyclic voltammetry electrochemical deposition technique, and obtain CdSe-TiO2nanotube array heterojunction composite films. The influence of parameters (electrolyte concentration, pH value and heat treatment temperature) during the processing of preparing CdSe-TiO2nanotube array heterojunction composite films on the microstructure, morphology, optical absorption and photoelectric properties were investigated by characterization methods (X-ray diffraction, scanning electron microscopy) and test methods (diffuse reflectance UV-Vis spectrometer and photocurrent test). The experimental results are as follows:XRD and SEM results show that the prepared TiO2nanotube arrays was highly order and uniformly distributed, whose diameter was about100nm and the length was800nm; cubic phase CdSe nanoparticles of20nm were distributed uniformly on the inner and outer wall of TiO2nanotubes, which greatly increased the contact area between TiO2nanotubes and CdSe particles. The absorption spectra of diffuse reflectance UV-vis shows that compare with the TiO2nanotube array films, the light absorption properties of CdSe-TiO2nanotube array films improved ramarkably under simulated visible light irradiation. When SeO2concentration is4mmol/L, pH value is3, the light absorption properties of CdSe-TiO2nanotube arrays composite films were the best after heat treated at350℃The results of photoelectric performance testing indicate that CdSe-deposited TiO2nanotube films generated remarkablely photocurrent density under visible light irradiation. When the concentration of SeO2is4mmol/L, the pH value is3, the heat treatment temperature is350℃, the photocurrent density of CdSe-TiO2nanotube arrays composite films were the best, and the maximum photocurrent density of CdSe-TiO2nanotube arrays composite films increase90times than that of TiO2nanotube array films.