Electrochemical behavior of MgCl2 and co-deposition mechanisms of Mg and Sr in SrCl2−KCl−MgCl2 melt

Abstract

The electrochemical behavior of MgCl₂ and the co-deposition mechanisms of Mg and Sr in the SrCl₂−KCl eutectic system were evaluated using various electrochemical techniques, including cyclic voltammetry (CV), square wave voltammetry (SWV), and open-circuit potential (OCP) analysis. It was observed the Mg(II) reduction on the tungsten electrode in SrCl₂−KCl melt occurred in a single-step process involving the transfer of two electrons, exhibiting a quasi-reversible mode. The electrochemical co-deposition of Mg and Sr in the SrCl₂−KCl−MgCl₂ melt involved the formation of two types of Mg−Sr intermetallic compounds. The evolution in the co-deposition mechanism of the nucleation type with changing overpotential was explored through chronoamperometry (CA). It is shown that the nucleation pattern on the electrode surface was depended on the substrate materials and the electrode reaction products. Early-stage nucleation was attributed to Mg(II) reduction under all overpotential conditions. With the co-deposition of Mg and Sr, Mg(II) was reduced to form the Mg nucleus on the electrode surface, followed by underpotential deposition of Sr(II) on the Mg surface accompanied by Mg deposition simultaneously. Additionally, increasing MgCl₂ concentration in the SrCl₂−KCl melt resulted in a higher current density during the Mg−Sr co-deposition process.