Research Titania Nanotube Preparation, Modification And Photocatalytic Properties

TiO2is one of the most promising photoanodes in solar water splitting system, because of its low cost, nontoxicity and stability. However, the Solar-To-Hydrogen (STH) efficiency of TiO2is substantially limited by its large band gap energy and usually fast electron-hole recombination. In this work, the Anodic Titanium Oxide nanotube films (ATO) were successfully modified to enhance the photocatalytic activity and expand ATO nanotubes optical absorption spectrum into the visible.Firstly, the ATO nanotubes were prepared by anodization and the impact of preparations parameters including the composition of electrolyte, voltage, temperature on the growth of ATO nanotubes was research. The results indicate that the growth rate becomes fast with the voltage increased, at the same electrolyte system, while the outer diameter of nanotubes increases and then trend to saturation; temperature only affects the growth rate of nanotubes; A key factor in the preparation of large outer diameter of ATO nanotubes is the water content of electrolyte, the outer diameter becomes more large with the water content increased. In addition, the optimum measurement conditions and preparation technology based on the photocatalytic properties are determined.Secondly, Au nanoparticles were successfully loaded on the ATO nanotubes by sodium citrate reduction method and deposition-precipitation with NaOH method on the basis of the above experiment. The results show that Au nanoparticles obtained by sodium citrate reduction method exhibit un-uniformly distribution, round and larger diameter; the Au nanoparticles obtained by deposition-precipitation with NaOH have smaller diameter, uniformly distribution and larger loading area. ATO-Au nanotubes prepared by deposition-precipitation with NaOH method expand the visible light absorption into550nm, the Au loaded nanotubes have much larger photocurrent density than pure ATO nanotubesFinally, we first report electrochemical reductive doping method to modify ATO nanotubes for photoelectrochemical (PEC) water splitting, followed by the analysis of the morphology, crystalline structure and PEC properties. The results show that the morphology and crystalline structure of the hydrogenated ATO nanotubes have no change, the Raman peaks exhibit slightly blue shift, and the conductivity improve, due to the introduced oxygen vacancies. The photoelectrochemical performance indicates that, compared to the pure ATO nanotubes, the hydrogenated ATO nanotubes have enhanced photocurrent density under the irradiation of the AM1.5G solar light. The incident-photon-to-current-conversion efficiency measurements show that the enhanced photocurrent in the hydrogenated ATO nanotubes mainly attributed to the improved photoactivity in the UV region.