Fabrication and formation mechanism of self-organized TiO_2 nanotube arrays

Self-organized TiO2 nanotube arrays were fabricated by a one-step electrochemical anodization process on a Ti sheet.The prepared samples were annealed in air and detected by SEM,XPS and UV-vis DRS spectrophotometry.And the possible formation mechanism was presented.The results show that the well ordered TiO2 nanotube arrays with the average tube diameter of 150 nm and the average tube length of 400 nm were fabricated under optimized electrolyte and oxidation conditions.The TiO2 nanotubes exhibit strong absorption in visible-light region of 400-700 nm.The fluorine with an molar fraction of 0.35% is doped into TiO2 nanotubes,as evidenced by XPS.The removal efficiency of AO7 by the F-TiO2 nanotube arrays annealed at 673 K reaches 37.2 % under visible light irradiation.