Electrochemical reaction-induced thermal convection in molten LiCl-KCl

Abstract

Understanding the natural convection in molten salt electrochemical systems is of great importance to accurately reveal the reaction kinetics and mechanism. This electrochemical reaction would cause changes in the density and temperature of salt near the electrode due to the depletion of reactant and the generation of product. However, in most studies, the temperature-induced convection effects received very limited attention in molten salts as the experiments were usually conducted in a thermostatic furnace. Herein we report the electrochemical reaction-induced convection in molten LiCl-KCl, with reactive EuCl3 or CrCl3 added into the system. On the basis of numerical simulations for chronoamperometry, it was proved that the thermal convection effects were not comparable to the density-driven convection even at molten salt containing 100 mM redox concentration and an electrolysis time of 100 s. Nevertheless, we observed the enhancement of density-driven convection by thermal convection in cyclic voltammetry simulation in LiCl-KCl-CrCl3 system at 5 mV/s. Furthermore, the simulated results revealed that the temperature difference between electrode and solution ranged from 2.94 × 10−3 to ∼ 0.4 K at the applied conditions, showing the negligible change in temperature caused by electrochemical reactions.