Effects of heat treatment scheme on the photocatalytic activity of TiO ₂ nanotube powders derived by a facile electrochemical process

TiO₂ nanotubes (NTs) in powder form were synthesized by a facile electrochemical process in a perchlorate-containing electrolyte. Transmission electron microscopy results indicate that the TiO₂ NT-powder is in an amorphous structure and has outer diameter of 20 nm and tube-wall thickness of 5 nm. X-ray diffraction analysis reveals that phase composition of the annealed TiO₂ NT-powders is related to the heat treatment scheme. Methyl orange was employed as a representative dye pollutant to evaluate the ultraviolet photocatalytic activity of the TiO₂ NT-powders. It was found that different post heat treatment schemes affect greatly the photocatalytic activities of the TiO₂ NT-powders, which should be ascribed to the changes in phase structural and morphological properties of the TiO₂ NT-powders. These results indicate that there should be a balance between crystal phase and nanotubular configuration for achieving the best photocatalytic activity of the TiO₂ nanotube powders.