Effects of the Structure of TiO[sub 2] Nanotube Array on Ti Substrate on Its Photocatalytic Activity

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Abstract
A novel oriented TiO2TiO2 nanotube (TN) array on Ti substrate was fabricated by using an electrochemical method. The structure and surface morphology of the TN array was examined by Raman spectroscopy and scanning electronic microscopy, respectively. The photocatalytic activity of the TN arrays was evaluated by the removal of methylene blue in aqueous solution. The effects of structure and morphology of the TN array on its photocatalytic activity were investigated. It was observed that the crystal structure, morphologies, and nanotube sizes were greatly influenced by anodization voltage and calcination temperature. The shift of absorption edges shorter wavelengths were ascribed to the quantum effect of the tube wall thickness. The TN arrays prepared at 20V20V and calcined at 450°C450°C have the highest photocatalytic activity due to an increase in the anatase crystal phase and an increase in surface area. When the calcination temperature was higher than 450°C450°C , the photocatalytic activity of the TN array decreased, which was ascribed to excessive rutile content and a decrease in surface area resulting from the sintering and growth of TiO2TiO2 crystallites.