The electrochemical behavior of UCl 4 and UCl 3 in LiCl-KCl eutectic melt was studied at 723-823 K by different electrochemical methods. Electroreduction of U͑IV͒ in LiCl-KCl melt occurs via two successive steps involving transfer of one and three electrons. The diffusion coefficients of U͑IV͒ and U͑III͒ were determined by linear sweep voltammetry, chronopotentiometry, and chronoamperometry. The values found by these methods are in a good agreement with each other. The standard rate constants for the redox reaction U͑IV͒ + e − → U͑III͒ were calculated from cyclic voltammetry data and for the discharge process U͑III͒ + 3e − → U by using the impedance spectroscopy method. The values of constants testify that the redox process proceeds quasireversibly, mostly under diffusion control, while electrodeposition is mainly controlled by the rate of charge transfer. The formal standard potentials of E U͑IV͒/U͑III͒ * , E U͑IV͒/U * , and E U͑III͒/U * were determined by different electrochemical methods and some thermodynamic properties of UCl 4 and UCl 3 dissolved in a LiCl-KCl eutectic melt were calculated. The influence of oxide ions on the electrochemical behavior of the LiCl-KCl-UCl 4 melt was studied.

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