Electrochemical Behavior of Telluride Ions (Te^2-) in Molten LiCl-Li₂Te Solution at 650 °C

The electrochemical behavior of Te^2- ions was investigated in the LiCl-Li₂Te binary on glassy carbon electrodes at 650 °C as a means to understand the fundamental thermodynamic and mass transport properties of Te^2- ions. Cyclic voltammetry and constant-potential electrolysis confirmed an electrochemically reversible, two-electron soluble-insoluble reaction of Te^2-/Te(l). The formal potential for the Te^2-/Te(l) reaction was determined to be 1.744 V vs Li⁺/Li(l), and the diffusivity of Te^2- ions was about 0.44-1.25 × 10^-5 cm² s^-1. The low value for diffusivity relative to those of other cations in molten salts suggests the possibility of forming complex ions such as [Li₈Te]⁶⁺ due to strong chemical interactions with Li⁺ ions in the electrolyte. The anodic polarization of Te(l) indicated that the formation of TeCl₂(g) and the cathodic polarization of Te(l) involved the codeposition of Li metal into the Te(l). The results of this work provide essential knowledge in developing electrochemical processes for separation of tellurium as well as in mitigating the degradation reactions with structural materials.