Characteristics of TiO 2 Nanotubes Fabricated by High-Frequency Cyclic Anodization

This study investigates the fabrication of TiO 2 nanotubes (TNTs) using the cyclic anodization of Ti foil with high frequency. High-frequency cyclic anodization with increasing duty cycles yields longer, larger, and more regular TNTs, but the walls of the TNTs are thinner. The photocatalytic degradation of methyl orange dye by TNTs indicates that a higher duty cycle during the fabrication of TNTs yields improved performance. For example, the reaction rate constant with a 75% duty cycle (0.0151 ± 0.0003 min −1 ) is 1.28 times higher than that with a 0% duty cycle (0.0118 ± 0.0018 min −1 ). It only takes half the time for a 75% duty cycle to reach 70% degradation percentage as compared to, that for the 0% duty cycle. Nevertheless, high-frequency cyclic anodization with increasing duty cycles tends to generate more nanograss on the TNTs and causes a reduction in the TNT strength. Additionally, increasing the duty cycle yields few improvements in the photocurrent and the preferential orientation of anatase TNTs.