Selection About Molten Salts Used For The Electrochemical Reduction of Porous TiO2 pellets

Diagrams of the equilibrium potential E (relative to the standard chlorine electrode) against the activity of oxide ion ( expressed as its logarithm, pO2−) in systems of Ti-O-Cl-M (M=Li, Na, Mg, Ca, Sr and Ba) were plotted to investigate the electro-deoxidation of porous TiO2 pellets in different chloride molten salts, including LiCl, NaCl, MgCl2, CaCl2, SrCl2 and BaCl2. From the diagrams, the reduction pathways of TiO2 in different molten salts are similar; and the applied potential (vs Cl−/Cl2) on the cathode and O2− ion activity influence greatly on the reduction pathway of TiO2 and the deoxidation limit. To test and verify the results of the thermodynamic analysis, electro-deoxidation experiments in different molten salts were done to determine the actual pathways in the electrochemical reduction of TiO2 and the possible deoxidation limits in the molten salts. The results indicated that the thermodynamic analysis is helpful in predicting and understanding the electrochemical reduction process of titanium oxides though the experimental results differ slightly from the thermodynamic analysis in some systems. Low-oxygen Ti can be obtained only in molten CaCl2.