Electrochemical characterization of reduced TiO2 thin films in acetonitrile electrolytes

The synthesis of reduced TiO 2 is usually achieved under an H 2 atmosphere at high temperatures and pressures. In this work, we report a new electrochemical method that allow the reduction of TiO 2 -P25 in soft conditions by applying pulses of potential using an acetonitrile-containing electrolyte saturated with H 2 . The reduction of TiO 2 and intercalation of H + were more effective at very low concentrations of water in acetonitrile and in the presence of hydrophobic electrolytes such as tetrabutylammonium hexafluorophosphate. Raman spectroscopy confirms the insertion of H + during the reduction of TiO 2 . The reduced TiO 2 -P25 showed a five-fold increase in photocurrents in comparison with pristine TiO 2 -P25. AC voltammetry and electrochemical impedance spectroscopy provided valuable information to analyze the structure of the conduction band, the electron transfer kinetics, and the electron transport through the TiO 2 film. Finally, the stability of reduced TiO 2 under oxidizing potentials was studied. • TiO 2-x can be synthetized in soft conditions using pulses of potential in the presence of H 2 dissolved in acetonitrile. • The reduction of TiO 2 is more effective in the presence of hydrophobic electrolytes dissolved in acetonitrile. • TiO 2-x show a five-fold increase in the photocurrents in comparison to pristine TiO 2 . • AC techniques are very useful to study the conduction band structure of nanostructured TiO 2 electrodes.