Direct electrochemical reduction of titanium dioxide in Lewis basic AlCl3–1-butyl-3-methylimidizolium ionic liquid

The direct electrochemical reduction of titanium dioxide (TiO2) to metallic titanium at room temperature is firstly studied in Lewis basic AlCl3–1-butyl-3-methylimidizolium (AlCl3–BMIC) ionic liquid. In this study, cyclic voltammetry, potentiodynamic polarization, sampled current voltammetry and X-ray photoelectron spectroscopy (XPS) techniques were utilized. Analysis of the cyclic voltammetry suggested that TiO2 film can be reduced to metallic Ti. The sampled current voltammetry was applied to elaborate the reduction mechanism and the results showed that this reduction process may include two steps. When the output potential difference of 2.8 V was applied, a TiO2 cylindrical pellet was partly reduced to metallic Ti. However, due to the very slow reaction rate, there was only about 12 wt% of TiO2 was reduced during the electrolysis time of 48 h. It was predicted that the process for the direct reduction of solid TiO2 would be explained as follows: given enough cathode potential, the reduction happened at the cathode/ionic liquids interface, where the oxygen was ionized, then dissolved in the ionic liquid and discharged at the anode, with the metallic Ti left at the cathode.

► Direct electrochemical reduction of TiO2 to metallic Ti at room temperature in Lewis basic AlCl3-1-butyl-3-methylimidizolium (AlCl3-BMIC) ionic liquid was found to be promising.
► The thicker is TiO2 film; the more negative is cathode polarization potential. Therefore the bulk TiO2 needs greater cathode reduction potential.
► The reduction process may include two steps.