Monitoring Internal Oxygen Partial Pressure in YSZ Electrolyte Under Electrolysis Cell Mode Using 4-Electrode System

Abstract

When solid oxide cells are operated in electrolysis mode, high oxygen pressures can be developed in electrolyte near the oxygen electrode/ electrolyte interface, leading to oxygen electrode delamination. Monitoring oxygen partial pressure in the electrolyte is necessary for the prevention of catastrophic failure in solid oxide electrolysis cells (SOECs). In this study, we applied four-electrode system to fuel electrode-supported SOECs. Four–electrode consists of air electrode, fuel electrode, Pt probe embedded in electrolyte and Pt reference electrode on the electrolyte edge. We measured internal electric potential near the oxygen electrode with respect to the reference electrode using embedded Pt probe. Based on this experimental setup, internal partial pressure of oxygen at the Pt probe location was determined. As tracing changes in internal oxygen partial pressure with varying overvoltage or current density, we investigated the relationship between operating conditions and the tendency of chemo-mechanical failure in solid oxide electrolysis cells.