Oxygen reduction mechanism of NdBaCo2O5+δ cathode for intermediate-temperature solid oxide fuel cells under cathodic polarization

The oxygen reduction reaction mechanism of NdBaCo2O5+δ cathode for intermediate-temperature solid oxide fuel cells was investigated by the electrochemical impedance spectroscopy under cathodic polarization. The Nyquist diagrams showed the different changes with the applied cathodic voltage at three temperature ranges: at 500 and 550 °C, at 600 °C, at 650 and 700 °C, which might be related to the changes in the charge transfer and/or oxygen diffusion processes including O2 adsorption/desorption. Besides, the diffusion process was more easily affected by the increase of applied cathodic voltages than the charge transfer process, which was ascribed to the low activation energy of the diffusion process.