Investigation on electrochemical behaviors of MgCl2 impurity in LiCl-KCl melt

Abstract

In this work, the electrochemical behaviors of impurity Mg(II) in LiCl-KCl melt were investigated at 673 K by using cyclic voltammetry (CV), chronopotentiometry (CP) and square wave voltammetry (SWV) techniques. Results showed that the semi-integral curve derived from CV measurements revealed that the reduction of Mg(II) was a quasi-reversible process. And the standard reaction rate constant of the order ≈10 −3 cm s −1 , calculated by Nicholson method, which showed that the redox reaction of Mg was in the quasi-reversible range of Matsuda-Ayabe standard. The EMF measurements were applied to measure the apparent standard potential and activity coefficient of Mg(II). According to the standard apparent potentials at various temperatures, the values of enthalpy and entropy changes were −673.3302 ± 4.3997 kJ mol −1 and 0.1930 kJ mol −1 K −1 , respectively. Chronoamperometry (CA) results showed that deposition of metal Mg on the W electrode was an instantaneous nucleation process under diffusion control. Additionally, the diffusion coefficients calculated by CP revealed that the temperature dependence obeyed the Arrhenius law. And the activation energy for diffusion of Mg(II) is 44.73 kJ mol −1 .