# Electrochemical Properties of NdCl3 and CeCl3 in Molten LiCl-KCl Eutectic Salt
## 1 Introduction  
Numerous studies have focused on the research and development of the pyroprocessing technology for safe and proliferation resistance reprocessing of spent nuclear fuel [1; 2]. Electrochemical-based methods of reductive extraction are used as pyrochemical separation processes [3; 4; 5]. Pyrochemical separation from molten salt is considered a suitable alternative method to aqueous processes for the separation of minor actinides from the rest of the fission products containing lanthanides [6; 7]. For this reason, the assessment of accurate electro- and thermochemical data of lanthanides is of high importance. Success in the electrorefining process requires reliable data on the electrochemical behavior and thermodynamic data of lanthanides in these media. Recently, many studies on the electrochemical behavior of uranium using CV (Cyclic voltammetry), CP (Cyclic Potentionmetry) and anodic stripping voltammetry in the LiCl-KCl eutectic salt have been focused on low concentrations up to ~4.7 wt% UCl3 [8]. Thermodynamic and transport properties of binary LnX3-MX systems have been investigated widely [9; 10; 11], where Ln = Ce, Nd, La, Pr, Gd; M = Li, Na, Cs, and X = F, Cl, I, and Br. The addition of lanthanide chloride to alkali metal chloride results in the formation of a variety of stoichiometric compounds. The formation of compounds and complexes in the molten salt system affects the electrical conductivity and other thermo-physical properties [12]. Recently, [PERSON] and coworkers reported the electrochemical behavior of a series of lanthanide elements in LiCl-KCl eutectic melt in the temperature range of 400-550 \({}^{\circ}\)C [7]. Most of the reports available in the open literature pertain to the electrochemical behavior of individual element of the lanthanide series at dilute concentrations [12]. [PERSON] investigated chronopotentionmetry to determine diffusion coefficient of CeCl3 at various temperature. [PERSON] and [PERSON] measured apparent standard potentials and diffusion coefficients of CeCl3 by cyclic voltammetry methods [13; 14]. Additionally, [PERSON] conducted the emf method to determine the apparent standard redox potential of NdCl3 in fused LiCl-KCl eutectic at a different temperature [15; 16; 17]. However, the effect of the presence of multiple components alongwith moderate to high concentrations in the same electrolyte has not been largely investigated in detail. Furthermore, the thermodynamic properties of lanthanides in the LiCl-KCl are not known at various temperatures. In this report, we present results of an investigation of individual species electro-and thermo-physical properties of Nd\({}^{3+}\)/Nd and Ce\({}^{3+}\)/Ce in LiCl-KCl eutectic molten salt. The effects of NdCl\({}_{3}\) and CeCl\({}_{3}\) concentrations on the diffusion coefficient, activity coefficient and activation energy are currently being studied to enhance the fundamental knowledge of how electrochemical behavior, specifically for CeCl\({}_{3}\) or NdCl\({}_{3}\) contents ranging from 4 wt% to 10 wt% in LiCl-KCl eutectic salt at 753 to 793 K. Moreover, in ternary systems, there are various concentration-dependent effects that have not been previously reported in literature. Therefore, the main objective in this study is to explore electrochemical and thermodynamic behaviors of cerium (Ce) and neodymium (Nd) in high concentration ranges (4 wt% to 10 wt%) of LiCl-KCl eutectic salt by utilizing electrochemical transition techniques, such as cyclic voltammetry (CV) and chronopotentionmetry (CP).