Preparation Of Long TiO₂ Nanotube Arrays And The Catalytic Degradation Performance

TiO2 nanotubearrays (TNTAs) has high-aspect-ratio with good control of morphology. Such structure not only provides channels to enhancing electron and iron transfer but also has an active effect on the infiltration of interacted materials. However, the fast recombination rate of photogenerated electron-hole pairs in pure TiO2 nanotubearrays, the surface bundlings and the low quantum yield of photochemical conversion for solar energy severely hinder the industrialized applications of TiO2 nanotube arrays.In this dissertation, long TiO2 nanotube arrays were synthesized by the electrochemical oxidation method and the metal iron modification were operated by vacuum sequential chemical bath deposition. The XRD, UV-Vis, SEM, TG, UV, EDS were performed to characterize the morphology, crystalline phase, photo-absorption ability of TiO2 nanotube arrays. Results were listed as follows:(1) Self-organized titania nanotube arrays were synthesized using electrochemical anodization method after preliminary treatment of titanium foil. The influences of the electrolyte composition and electrolyte temperature on the formation of TiO2 nanotube arrays were investigated in detail and the growth mechanism were analyzed. The results indicated that all electrolytes (HF solution, C6H12O6-NH4F solution, isopropanol-NH4F solution) could be used to form the TiO2 nanotube arrays except propylene glycol. Within the same time, the bigger concentration of ethylene glycol is, the larger diameter and longer titania nanotube arrays are observed.30℃ was proved to be the optimal temperature to form TNTAs in the electrolyte of ethylene glycol.(2) Ultrasonic wave was used to clean the bundlings on the surface of TiO2 nanotube arrays. Different ultrasonic mediums, i.e., distilled water, acetone and isopropanol, were investigated respectively. The results indicated that ultrasonic medium had a great influence on the removal effects. Surface tension and viscosity of the medium were considered to be two factors for the surface cleaning. Acetone was found to be more suitable than water and isopropanol. TiO2 nanotubes under 30min ultrasonic treatment exhibited ordered morphology and the best photocatalytic activity. Meanwhile, the mechanism of different mediums’effect were explored.(3) TiO2 nanotube arrays modified by Fe with high sensibility in the visible spectrum were prepared by annealing anodic TiO2 nanotube arrays pre-loaded with Fe(OH)3 using vacuum sequential chemical bath deposition (VS-CBD). The photocatalytic activities of the high aspect-ratio TiO2 nanotube arrays are evaluated by the decolorization of methylene blue (MB). Compared with the TiO2 nanotube array films without any doped element, the nanotube array films doped Fe exhibit a higher photocatalytic activity.