Electrochemical Characterization of Ag-Y0.5Bi1.5O3 Composite Cathode on 8YSZ-Ce0.78Gd0.2Sr0.02O2-δ Electrolyte Using AC Impedance Spectroscopy

The electrochemical performance of Ag-Y_0.5Bi_1.5O₃ (YSB) cathodes on Ce_0.78Gd_0.2Sr_0.02O_2-δ (GDCS) electrolyte with an epitaxial Y_0.16Zr_0.84O_1.92 (8YSZ) thin film outer layer was estimated using electrochemical impedance spectroscopy (EIS). A series of bismuth oxides with different silver contents were prepared and measured by an impedance spectroscopy on symmetrical cells in the temperature range from 500 °C to 650 °C. The microstructural analyses of porous composite cathodes and bi-layer electrolyte with fluorite structures were investigated by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that silver in the cathode reduces the surface resistance which improves the efficiency of current collection from the cathode. Besides, the bi-layer electrolytes have lower activation energy than GDCS electrolytes. Without topping Pt or silver metallic working electrode, the 50-70 vol% of Ag powder mixed with a submicron size YSB powder exhibited much lower overpotential and higher exchange current density than Lanthanum Strontium Cobalt Ferrite perovskite cathodes below 650 °C.