Oxide Electrodes at High Temperatures

Abstract

High temperature fuel cells and electrolysers based on solid yttria stabilized zirconia electrolytes typically operate at 1000°C to reduce polarization losses. Much of the published work on electrode reactions has been carried out on precious metal electrodes (1–4). Using point contact electrodes eliminates the contribution of concentration polarization due to mass transport (5,6). The rate controlling step in the electrode reaction at 1000°C is the adsorption-desorption of oxygen (1,2,7,8). Oxide electrodes exhibited marked time dependence of polarization. Base metal oxide electrodes defect structures depend on oxygen partial pressure. The hysteresis is then associated with the slow equilibration of the defect structure with the applied overpotential (9,10). The present paper extends the application of the model and presents conclusions which can aid in high temperature electrode design.