In-situ preparation of multi-layer TiO2 nanotube array thin films by anodic oxidation method

The multi-layer TiO2 nanotube array thin films have been formed by anodic oxidation method via adjusting the outer voltage during oxidation process in glycerol electrolyte containing 0.3% NH4HF2. The diameter of the nanotube array increases with the outer voltage, and the length of nanotube in every layer increases with the anodic oxidation time. These multi-layers bring new possibilities to tailor the properties of the TiO2 nanotube array thin films formed via anodic oxidation method. Further, such multi-layer structure provide a new approach to evaluate the growth rate of TiO2 nanotube, which will help us to understand more deeply the formation mechanism of the TiO2 nanotubes. The growth rate of TiO2 nanotube array is respectively 1.2 and 3.6 mu m/h under the anodic voltage of 30 V and 60 V. These multi-layer TiO2 nanotube array thin films may exhibit lots of potential applications in photoelectrochemical fields. (C) 2011 Elsevier B.V. All rights reserved.