Electrochemical characterization of reduced TiO2 thin films in acetonitrile electrolytes

The synthesis of reduced TiO2 is usually achieved under an H2 atmosphere at high temperatures and pressures. In this work, we report a new electrochemical method that allow the reduction of TiO2-P25 in soft conditions by applying pulses of potential using an acetonitrile-containing electrolyte saturated with H2. The reduction of TiO2 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 TiO2. The reduced TiO2-P25 showed a five-fold increase in photocurrents in comparison with pristine TiO2-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 TiO2 film. Finally, the stability of reduced TiO2 under oxidizing potentials was studied.