Improve titanate reduction by electro-deoxidation of Ca3Ti2O7 precursor in molten CaCl2

Abstract

The low O2− diffusion rate in the electro-deoxidation of titanium containing compounds by either the OS process or the FFC process leads to a low reaction speed and a low current efficiency. In this study, Ca3Ti2O7 was used as a precursor to improve the reduction speed of titanium. Because of the greater number of “diffusion channels” created in cathode as Ca2+ liberates from Ca3Ti2O7 precursor in the electro-deoxidation process, the O2− diffusion rate was improved significantly by using Ca3Ti2O7 instead of CaTiO3 as precursor. Parallel constant voltage electrolysis (3.2 V) confirms that Ca3Ti2O7 and CaTiO3 are reduced simultaneously because of their similar crystal structures. However, the reduction area of Ca3Ti2O7 spreads much faster than that of CaTiO3, indicating a difference in the O2− diffusion rate. Constant voltage cyclic voltammetry (CV) and theoretical analysis of the crystal structure were also conducted to compare the differences between Ca3Ti2O7 and CaTiO3. The results indicate that using a precursor with a greater number of soluble cations, titanium reduction speed can be greatly improved in the electro-deoxidation process. Finally, a new electrolysis method for converting and recycling excess CaO from the Ca3Ti2O7 precursor was proposed.