Redox behaviour of cerium oxychloride in molten MgCl2–NaCl–KCl eutectic

The electrochemical behaviour of cerium oxychloride in MgCl2–NaCl–KCl ternary eutectic was investigated by cyclic voltammetry at 823 K. The cyclic voltammogram of UO2Cl2–CeOCl in MgCl2–NaCl–KCl eutectic shows two peaks during the cathodic sweep as well as anodic sweep. The reduction of UO22+ is by a single step two-electron transfer and that of CeO+ is by a single step one-electron transfer. The reduction of CeO+ was found to be quasi-reversible.The reduction potentials of UO22+/UO2 and CeO+/CeO versus Ag(I)/Ag reference electrode at 823 K are 0.103 and −0.299 V, respectively. The diffusion coefficient of CeO+ at 823 K is in the range of (1.7–1.9) × 10−5 cm2 s−1. The cyclic voltammogram for 0.015 mol% CeOCl shows an additional peak during the anodic sweep at −0.056 V, which is being attributed to monolayer dissolution of CeO at the glassy carbon working electrode. Electrochemical impedance data of 0.015 mol% CeOCl in MgCl2–NaCl–KCl eutectic at the open circuit potential was fitted to a Randles cell from which the heterogeneous rate constant was estimated. X-ray photoelectron spectroscopy was used to confirm that the oxidation state of cerium in the eutectic is +3.