Electrochemical measurements of diffusion coefficients and activity coefficients for MnCl₂ in molten eutectic LiCl-KCl

An electrochemical study of manganese chloride in molten salt mixtures of eutectic LiCl-KCl was carried out using a variety of electrochemical methods in a high temperature cell including cyclic voltammetry (CV), chronopotentiometry (CP), chronoamperometry (CA), and open circuit potentiometry. Single step reduction from Mn²⁺ to Mn(0) was observed on both W and Mo working electrodes. Using a combination of these methods, measurements were made of activity coefficient and diffusion coefficient for MnCl₂ in LiCl-KCl as a function of concentration (3.54 × 10⁻⁴ to 3.60 × 10⁻³ mol fraction of MnCl₂) at 773K. From OCP measurements, values for activity coefficient varied from 0.014 to 0.0071. Diffusion coefficients varied with concentration and differed based on measurement method (CV, CA, or CP). Based on cyclic Mn(II) ranged from 1.1 to 2.8 × 10⁻⁵ cm²/s depending on concentration.