Measurement of Chemical Potential in Bcy Electrolyte with Varying Thickness and Configuration Using Embedded Reference Electrodes

Abstract

The correlation between internal chemical potential, and durability of anode-supported BCY (yttria-doped barium cerate) electrolyte cells, was investigated as a function of electrolyte thickness and configuration. Internal hydrogen and oxygen chemical potentials were measured using embedded Pt probes. As the electrolyte thickness decreased, the internal chemical potential became dominated by the gases surrounding the cathode, indicating that the thin BCY cell may be vulnerable to water vapor produced at the cathode during operation. BCY cells with BZY (yttria-doped barium zirconate) protecting at the cathode side (bi-layer cells) showed a small chemical potential variation through the electrolyte region close to the electrode side, indicating significant electronic conduction.Constant-current tests were conducted on thin (~ 10 µm) and thick (~ 35 µm) BCY single layer cells, and also on BCY-BZY bi-layer cells, especially under negative voltage conditions. Consistent with the results of the internal chemical-potential measurements, the thin BCY single layer cell showed a significant rate of degradation due to changes in BCY composition in the electrolyte and cathode, while the thick BCY single layer cell showed much better durability, regardless of the sign of cell voltage. The bi-layer cell was stably operated under any severe operating conditions, because of the BZY protecting layer against water vapor’s attack and its significant electronic conduction close to the cathode/electrolyte interface. Thus, the present work shows the effect of BCY electrolyte thickness and configuration on the durability of BCY based cells, in terms of their internal chemical potential.