Electrochemical characterization of Co-doped Sr0.8Ce0.2MnO3−δ cathodes on Sm0.2Ce0.8O1.9-electrolyte for intermediate-temperature solid oxide fuel cells

Electrochemical properties of Co-doped Sr0.8Ce0.2MnO3−δ cathode were investigated at the cathode/Sm0.2Ce0.8O1.9 electrolyte interface. The electrochemical impedance spectroscopy was measured under applied cathodic voltages (E = −0.4 to 0 V). At E = 0 V, the area-specific resistance decreased from 2.20 Ω cm2 to 0.19 Ω cm2 at 700 °C with Co doping. Under the cathodic polarization, the rate determining step of oxygen reduction process was different for both cathodes: the charge transfer for Sr0.8Ce0.2MnO3−δ and the diffusion process for Sr0.8Ce0.2Mn0.8Co0.2O3−δ. Besides, the overpotential also decreased from 124 mV to 19 mV at the current density of 0.1 A cm−2 at 800 °C with Co doping. The improved electrochemical properties of Co-doped Sr0.8Ce0.2MnO3−δ can be ascribed to the formation of more oxygen vacancies and more active sites for oxygen reduction reaction.