Performance degradation of impregnated La0.6Sr0.4Co0.2Fe0.8O3+Y2O3 stabilized ZrO2 composite cathodes of intermediate temperature solid oxide fuel cells

Composite cathodes of La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) and Y2O3 stabilized ZrO2 (YSZ) are fabricated by impregnating the porous YSZ scaffold pre-formed on YSZ electrolyte substrate with a solution containing La, Sr, Co and Fe in desired composition. The performance stability of the cathodes is evaluated in air at 750 °C for up to 120 h by electrochemical impedance spectroscopy under the condition of open circuit. An insignificant small amount of resistive phase SrZrO3 is formed at 800 °C during cathode preparation; however, its volume is not further increased at 750 °C for 120 h, as indicated by the XRD results. The cathode polarization resistance (Rp) increases from 0.17 to 0.30 Ωcm2 after the 120 h test mainly due to the increase of the low frequency polarization resistance (Rp2), which characterizes the low frequency processes in the reaction of oxygen reduction. The morphology change of the well connected LSCF particles to dispersive and flattened configuration accounts for the increase of the Rp2 and in turn the degradation of cathode performance.