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

Electrochemical impedance spectroscopy (EIS), linear polarization (LP), Tafel and cyclic voltammetry (CV) were performed to investigate the exchange current density (i(0)) of U/U3+ reaction in LiCl-KCl eutectic salt under different UCI3 concentrations (0.5 wt%-4 wt%) and temperature conditions (723 K-798 K). 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 i(0) were varied from 0.0054A cm(-2) to 0.102 A cm(-2). For the LP and Tafel methods, i(0) values were determined from the linear fitting at small and large overpotential ranges of the current-potential curves. The measurement for i(0) via CV was done analogously to the LP method. All i(0) 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, i(0) 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 i(0) under various experimental conditions. (C) 2017 Elsevier Ltd. All rights reserved.