Characterization and Photocatalytic Activity of TiO2 Nanotube Films Prepared by Anodization

Titanium dioxide nanotube (TNT) arrays were prepared in electrolytes containing fluoride by anodic oxidation. Different preparation parameters were investigated in order to evaluate their effects on length and inner diameter of nanotube, including weight ratio of glycerol to water, anodization voltage, electrolysis time, bath temperature, and electrolyte solution pH. The well defined and highly ordered TNT arrays were formed in electrolyte containing 40, and 20% water. The inner diameter of TNT was observed to increase as anodization voltage increased across the range of 10-40V. The length of TNT was affected simultaneously by both anodization voltage and electrolysis time. The inner diameter and length depend on bath temperature below 60 degrees C. The morphology of TNT was well defined and highly ordered only at electrolyte solution pH of 6 across the pH range of 2-10. Photocatalysis of methylene blue showed that reaction rate constants by TNT films were higher than P-25 films at comparable thickness. Reaction rate constants by TNT films increased as film thickness increased, but the enhancement was retarded when the length of TNT reached 2200 nm which appeared to be the limited penetration of incident UV light.