Characterization of TiO2 nanotubes obtained by electrochemical anodization in organic electrolytes

TiO2 nanotubular structures were prepared by electrochemical oxidation performed in organic electrolytes containing fluorides protracted up to different times. After the annealing treatment, required to obtain crystalline structures, samples were submitted to morphological, electrical and photoelectrochemical analysis. The obtained results suggest that in the presence of porous structures such as nanotube arrays the photo catalytic behaviour of the samples cannot be simply explained considering the different specific areas, but also the electronic properties of the electrodes have to be taken into account. Electrochemical impedance spectroscopy was used to correlate the morphology of these structures with their electronic properties and their working mechanism in the presence of a light radiation. A schematic representation of the nanotube structures as consisting of two layers, compact and porous, proved to be appropriate to clarify the obtained results. (C) 2012 Elsevier B.V. All rights reserved.