Measurement and Analysis of Exchange Current Density for U/U3+ Reaction in LiCl-KCl Eutectic Salt via Various Electrochemical Techniques

Abstract

Electrochemical impedance spectroscopy (EIS), linear polarization (LP), Tafel and cyclic voltammetry (CV) were performed to investigate the exchange current density (i0) of U/U3+ reaction in LiCl-KCl eutectic salt under different UCl3 concentrations (0.5wt%–4wt%) and temperature conditions (723K–798K). The EIS spectra were measured by applying minimum overpotential from equilibrium potential and fitted to the proposed equivalent circuit. From the EIS experiments, the calculated values of i0 were varied from 0.0054Acm−2 to 0.102Acm−2. For the LP and Tafel methods, i0 values were determined from the linear fitting at small and large overpotential ranges of the current-potential curves. The measurement for i0 via CV was done analogously to the LP method. All i0 values have the linear trend with the change of concentration and temperature; however, these values measured by LP, Tafel, and CV methods are greatly influenced by the change in electrode surface area. Overall, i0 agreed within 33% relative error range with the EIS method being the most consistent and accurate in comparison to reported literature values. Dimensionless analysis was done on the EIS data sets providing insightful correlations for prediction of i0 under various experimental conditions.