Degradation Study of Yttria Doped Barium Cerate (BCY) Electrolyte in Protonic Ceramic Fuel Cells Under Various Test Conditions

Acceptor-doped barium cerate has been considered as a potential electrolyte material in solid oxide fuel cell because of its high proton conductivity at temperatures below 700⁰C.  However, despite its superior transport property, barium cerate cannot be practically used in fuel cell due to its poor chemical stability in the atmosphere of water vapor and carbon dioxide. In the present work, we fabricated two kinds of BCY based anode supported cells, 1) BCY single layer cell and 2) BCY/BZY bi-layer cell, and their stability and degradation mechanism were investigated and compared, especially under severe operating conditions such as a negative voltage and low air flow rate. Constant current (CC) tests were conducted on the cells under various operating conditions such as positive vs. negative cell voltage and high vs. low fuel/air flow rate. Constant current (CC) tests were conducted on the BCY single layer and BCY/BZY bi-layer cells under a negative well as well a positive cell voltage as a function of air flow rate. Before and after the CC tests, I-V curve and impedance spectra were measured and compared to trace any increase in ohmic and/or non-ohmic resistance of the cells. Post-material analyses were conducted using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) to find out any change in microstructure and phase after severe operations.