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) x 10(-5) cm(2) 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. (c) 2006 Elsevier Ltd. All rights reserved.