Using electrochemical impedance spectroscopy to compensate for errors when measuring polarisation curves during three-electrode measurements of solid oxide fuel cell electrodes

Abstract

The use of three-electrode techniques involving an independent reference electrode is invaluable in determining the overpotential losses at solid oxide fuel cell (SOFC) electrodes. However, there are numerous barriers to achieve the accurate measurement of such overpotentials in an SOFC. Furthermore electrochemical impedance spectroscopy (EIS) is commonly used to analyse the processes occurring on SOFC electrodes, and there has been considerable work in establishing viable three-electrode techniques for EIS experiments under open circuit conditions. However, the three-electrode techniques currently developed for EIS experiments are not well suited for conditions of high load, or changing gas compositions; either intentionally or under diffusion limiting conditions. This paper reports a solution for commonly used pellet cells, which mitigates these problems. The paper presents a method using EIS to correct for errors when measuring the working electrode overpotential during polarisation arising from a shift in the electrolyte current distribution from the primary to the secondary current distribution under load. This technique enables meaningful overpotentials to be calculated using experimentally simple cell geometries under conditions where they cannot normally be accurately measured.