The Preparation And Characterization Of Nano-heterojunction CdSe/TiO2Film

As one of important photocatalytic materials, TiO2has many excellent characteristics such as stable chemical property, low cost and harmless to human body, and it can realize the transformation of solar energy into electrical energy of chemical energy which could be used in daily life. However, the band gap of TiO2photocatalysis semiconductor is3.2eV, and its photocatalytic activity only plays a role in the ultraviolet band. Besides, the part of light which TiO2could be used only accounts for5%of the terrestrial sunlight which result in a relatively low utilization ratio of sunlight; In addition, photoproduced electrons and holes of the TiO2can combine easily, and the quantum efficiency of the absorption of light under the influence of this becomes low. Thus, broaden TiO2spectral response and effectively suppress the combination of photoinduced electron-hole pairs have become the focus in the study of TiO2photoelectric catalysis. In this paper, CdSe as a narrow band gap semiconductor was deposited on the surface of TiO2nanotubes to improve its optical and electrical properties. CdSe nanoparticles of TiO2nanotube films were prepared by electrochemical deposition method. The morphology, structure and the photoelectric catalytic properties of the modified TiO2nanotube were characterized by SEM, XRD, UV-vis absorb spectra,degradation of organic compounds and light current test. Experimental results show that:The formation of CdSe was affected by deposition potential, deposition time, electrolyte concentration. The microscopic morphology observation and XRD results show that:With the increasing of deposition voltage, a small amount of elemental Cd appeared and the particle size of CdSe decreased, meanwhile, the agglomeration of CdSe particles appeared; With the increasing of the deposition time, the amount of CdSe increases, it means that the layer of CdSe nanocrystals which covering the surface of TiO2nanotube becoming thicker; On the contrary, the increase of the electrolyte H2Se03concentration decreases the amount of CdSe nanocrystals.Uv-vis test results show that:CdSe nanocrystalline has obvious optical absorption at the wavelengh of above400nm. The strongest light absorption of the samples were obtained with the CdSe deposition potential, deposition time and the concentration of H2SeO3were-0.8V,3min and9mM, respectively.The results of photocurrent test indicated that the light response current of the CdSe nanocrystals-loaded TiO2nanotube films increased significantly than that of TiO2nanotube films under visible light irradiation and the maximum photocurrent values of composite films were obtained with the CdSe deposition potential, deposition time and the concentration of H2Se03were-0.8V,9min and18mM, respectively.Three kinds of the samples were involved the degration experiments under the simulated sunlight irradiation and the largest degradation ratio of methylene blue solution(up to16%) were obtained for the composite films with CdSe deposition potential, deposition time and the concentration of H2Se03were-0.6V,3mm and18mM, respectively.