Electrode Reaction of Cerium into Liquid Bismuth in the Eutectic LiCl-KCl

Abstract

The electrode reaction of Ce(III)/Ce couple in the eutectic LiCl - KCl, on a Bi liquid electrode, was investigated in the temperature range of 673 - 823 K. Cyclic voltammetry, using a Bi pool electrode, suggest a quasi - reversible behaviour of the system, and the values of the kinetic parameters, k0 and α, as well as the reversible half wave potential, Er 1/2, have been obtained. The differences between the equilibrium potential adopted by a Ce electrode and the Er1/2 observed with the same Ce(III) solution at the liquid electrode, were consistent with the activity coefficients of Ce in the liquid Bi phase taken from the literature. Because of the ease of application of cyclic voltammetry, it was suggested this to be used as a general method to obtain approximate values of the excess Gibbs energy change of Ce in liquid metal, and hence the partial molar enthalpy of mixing and the partial molar excess entropy. Electromotive force, emf, measurements for various intermetallic compounds in two - phase coexisting states were carried out using a Bi coated tungsten electrode. The activities and relative partial molar Gibbs energies of Ce were obtained for CeBi2 and CeBi. The relative partial molar entropies and enthalpies of Ce as well as the standard Gibbs energies of formation for the Ce - Bi intermetallic compounds were calculated.