Composition optimization of samarium strontium manganite-yttria stabilized zirconia cathode for high performance intermediate temperature solid oxide fuel cells

Sm0.5Sr0.5MnO3 (SSM55)-Y2O3 stabilized ZrO2 (YSZ) composite cathodes are prepared by solution infiltration of 10, 15, 18 and 22 wt.% of SSM55 into YSZ scaffold, designated as 10-, 15-, 18- and 22-SSM55 + YSZ, respectively; and the effect of composition and microstructure on the electrocatalytic activity of the cathodes for the oxygen reduction reaction (ORR) is investigated by using three-electrode and full cells. Increasing SSM55 loading in the YSZ scaffold increases the distribution uniformity and connectivity of the nano sized SSM55 particles and thus reduces the open circuit polarization resistance and increases the exchange current density of the composite cathode. 18 wt.% is the optimal composition, at which the polarization resistance is 0.172 Ω cm2 at 800 °C and beyond which the electrochemical performance is compromised. Cathodic current polarization reduces the polarization resistance of the 18-SSM55 + YSZ cathode at 800 °C by 5.0%, 26.9% and 38.7% under 200, 400 and 600 mA cm−2 for 12 h. A peak power density of 763 mW cm−2 is achieved at 800 °C using an anode-supported cell with the 18-SSM55 + YSZ cathode.