During the course of the present study, highly dense arrays of titanium oxide nanotubes (TON) were fabricated by anodization of titanium foil in aqueous fluoride solutions. The obtained TON arrays were then subjected to annealing and electrochemical treatment, followed by characterization using scanning electron microscopy, X-ray diffraction, cyclic voltammetry and electrochemical impedance (El) techniques. By combining the effects of annealing and cathodic potential treatment, the cyclic voltammetry shows that the TON arrays catalyze the hydrogen evolution in acidic medium. This catalytic activity was not observed when the rutile phase started to form in TON arrays. El results show that TON conductivity is substantially improved by cathodic potential treatment only when it contains the anatase phase. This was also confirmed by the cyclic voltammetric scan for the Fe(CN)(6)(3-)/Fe(CN)(6)(4-) couple, where a smaller peak separation between anodic and cathodic peaks was observed, rather than as-anodized TON. (C) 2011 Elsevier Ltd. All rights reserved.