Electrochemical studies on the redox mechanism of uranium chloride in molten LiCl-KCl eutectic

The reduction and oxidation processes on platinum and glassy carbon electrodes in molten LiCl-KCl eutectic containing UCl₃ were investigated by cyclic voltammetry (CV), chronopotentiometry and electrochemical impedance spectroscopy (EIS) in the temperature range 660-780 K. Two redox peaks have been observed in the cyclic voltammograms corresponding to the two redox reactions U(IV)/U(III) and U(III)/U which are found to be reversible and quasi-reversible, respectively. The reduction potentials of U(IV)/U(III) and U(III)/U are −0.325 and −1.490 V versus reference electrode (0.1 mol% AgCl in the LiCl-KCl), respectively at 700 K. Chronopotentiometric measurements confirm the three-electron transfer during the reduction of U(III) to U metal. Electrochemical impedance spectroscopy data at various potentials were interpreted either as diffusion, adsorption or reduction process by nonlinear fit of the impedance data to the simulated equivalent circuits.