A novel PrBaCo2O5+σ-BaZr0.1Ce0.7Y0.1Yb0.1O3 composite cathode for proton-conducting solid oxide fuel cells

PrBaCo2O5+sigma-BaZr0.1Ce0.7Y0.1Yb0.1O3 (PBC-BZCYYb) composite cathodes are prepared by repeating impregnation (up to 5 times) of PBC into BZCYYb scaffold for proton-conducting solid oxide fuel cells with Ni-BZCYYb anode and BZCYYb electrolyte. The single-cells are evaluated electrochemically at temperatures between 600 and 750 degrees C using humidified hydrogen (similar to 3% H2O) as the fuel and air as the oxidant, and the corresponding electrochemical impedance spectra of the cells acquired at open circuit voltage are analyzed by the distribution of relaxation time. The optimal PBC loading in the composite cathode is 36 wt%, which is obtained by 4 times of PBC impregnation and leads to the highest cell performance with a peak power density of 0.49 W cm(-2) and the smallest polarization resistance of 0.078 Omega cm(2) at 750 degrees C. With the decrease of temperature from 750 to 600 degrees C, the peak power density is decreased from 0.49 to 0.17 W cm(-2) and the polarization resistance is increased from 0.078 to 1.085 Omega cm(2), and the dominating processes of polarization are changed from those in the anode to the ones in the cathode.