Preparation and photocatalytic activity of TiO₂ nanotube powders derived by a rapid anodization process

TiO₂ nanotube powders as a photocatalyst for water processing were prepared by a rapid anodization process in a perchlorate containing electrolyte. Morphological and micro-structural properties of the TiO ₂ nanotube powders were carefully characterized. Results indicate that the TiO₂ nanotubes with high aspect ratio, perfect tubular architecture, and smooth surface were successfully synthesized by a one-step electrochemical process. It is also noted that the nanotubes grow rather rapidly and well ordered in bundles with about 3 μm in length, 15 nm in outer diameter, and 10 nm in inner diameter. Effects of synthesis temperature of water bath on the morphological properties of the TiO₂ nanotubes were also studied, and a crystalline transformation process from amorphous to anatase then to rutile was revealed as the annealing temperature rises. Methyl orange was taken as a model compound to confirm the photocatalytic activities of the as-synthesized TiO₂ nanotube powders with different crystal structures. It is found that when annealed at 550 °C, the TiO₂ nanotube powders with a mixing phase structure of anatase and rutile have the best photocatalytic degradation activity for the methyl orange aqueous solution.