Redox potential measurement of AgCl in molten LiCl-KCl salt using chronopotentiometry and potentiodynamic scan techniques

Abstract

Here we report an innovative application of chronopotentiometry (CP) and potentiodynamic scan (PD) techniques to the measurement of redox potentials in a molten salt. Commonly, a stable Cl2/Cl− reference electrode is achieved by direct injection of chlorine gas to a graphite electrode, which requires rigorous design and operation for the high-temperature system to be studied. Instead, in situ techniques (CP and PD) were introduced to generate chlorine gas on the working graphite electrode, which then acts as the chlorine gas source. The measurements of formal potential and activity coefficient of AgCl/Ag at different AgCl mole fractions (X = 0.0039 and X = 0.0145) and temperatures (723–823 K) in molten LiCl-KCl salt were carried out using these two techniques. Moreover, these simple methods can be applied to measure the equilibrium potentials, formal potentials and activity coefficients of other metal chlorides in molten chloride salt as well as in other molten salt systems. Keywords: AgCl/Ag reference electrode, Activity coefficient measurement, Chronopotentiometry, Potentiodynamic scan, Molten chlorides