Electrochemical behavior of Th(IV) on the bismuth electrode in LiCl–KCl eutectic

Abstract

The electrochemical behavior of Th(IV) on a bismuth electrode in LiCl–KCl eutectic was investigated by various electrochemical techniques, aiming at in-depth elucidation of basic electrochemical and thermodynamic properties of Th in molten salt. The results of cyclic voltammetry and coulometric titration indicated that the reduction of Th(IV) on a liquid Bi electrode occurred at −0.92 V (vs. Ag/AgCl) and was a one-step process with four electrons transferred. In addition, thermodynamic properties of Th in liquid Bi medium were evaluated by coulometric titration method in the temperature range from 723 to 798 K. The redox peaks of Bi2Th intermetallic compound were detected at −1.13 and −1.05 V, and the corresponding Gibbs free energy of formation was measured by open circuit chronopotentiometry (OCP). Finally, galvanostatic electrolysis (GE) was conducted on a liquid Bi electrode to extract Th from molten salt at 773 K. X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) were applied to characterize the composition and morphology of the products, and revealed the formation of Bi2Th intermetallic compound.