Degradation study of yttria-doped barium cerate (BCY) electrolyte in protonic ceramic fuel cells under various operating conditions

Abstract

Yttria doped barium cerate (BCY) electrolyte, Ni+BCY anode supported cells were fabricated, and their stability and the mechanism of their degradation were investigated through constant current tests under various operating conditions, especially negative cell voltage operation (with respect to degradation phenomenon due to cell imbalance in a series connected stack). The results of electrochemical tests (IV characteristics and impedance spectra) indicate that the degradation rate was significant when the cell was operated under higher current densities (regardless of the sign of cell voltage) and only the ambient air was used for the cathode. Post-material analyses revealed that microstructural and compositional changes were obvious in the BCY electrolyte and the BCY of the cathode functional layer because of BCY decomposition in the wet atmosphere at the cathode. Thus, the present work concludes that the degradation rate of BCYelectrolyte-based cell depends on operating conditions, i.e., the amount of current density (the water vapor production rate at the cathode) and the air flow rate (flushing water vapor at the cathode).