Electrochemical characterization of reduced TiO2 thin films in acetonitrile electrolytes

Abstract

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.