Electrochemical and thermodynamic properties of Nd (III)/Nd (0) couple at liquid Zn electrode in LiCl-KCl melt

Abstract

The electrode reactions of Nd (III)/Nd couple at liquid Zn and Zn-coated W electrodes in LiCl-KCl melt were investigated in the temperature range of 707–784K. In the both cases, the electrochemical reduction of Nd (III) was observed at a more positive potential than that on an inert W electrode, due to the low activity of Nd in the metal phase. Cyclic voltammetry (CV) recorded at the liquid Zn electrode suggests the existence of a quasi-reversible reaction. The activity coefficient and apparent standard potential have been obtained. On the Zn-coated W electrode, the formation of five obvious non-homogeneous Nd-Zn intermetallic compounds could be observed through CV and open circuit chronopotentiometry (OCP) measurements and the thermodynamics of these intermetallic compounds was also investigated. Electromotive force (emf) measurements for the Nd-Zn intermetallic compounds in two-phase coexisting states were also carried out in the temperature range of 707–784K. Moreover, the standard formation Gibbs energies and the standard equilibrium constant of each Nd-Zn intermetallic compound were also calculated and the thermodynamic stabilities of these compounds at our experimental temperatures were evaluated.