Sr-deficient medium-entropy Sr1-xCo0.5Fe0.2Ti0.1Ta0.1Nb0.1O3- cathodes with high Cr tolerance for solid oxide fuel cells

In this work, Sr-deficiency is proposed as an effective strategy to improve the oxygen reduction reaction (ORR) activity and Cr tolerance of medium-entropy Sr1-xCo0.5Fe0.2Ti0.1Ta0.1Nb0.1O3-delta (S1-xCFTTN, x=0-0.15) cathodes for intermediate temperature solid oxide fuel cells (IT-SOFCs). With proper Sr-deficiency, S0.95CFTTN possesses the highest electrical conductivity and fastest oxygen exchange kinetics within tested samples. The optimized cathode yields outstanding ORR activity with a polarization resistance of 0.024 omega cm2 at 700 degrees C, much lower than 0.037 omega cm2 for SCFTTN cathode. Based on these, an anode-supported cell with S0.95CFTTN cathode exhibits a peak power density of 1153.5 mW cm-2 at 800 degrees C, much higher than that with SCFTTN cathode. Moreover, the S0.95CFTTN cathode displays dramatically enhanced Cr tolerance ability, which is due to the Sr deficient diminishes surface Sr segregation and subsequent the formation of SrCrO4. Our results indicate appropriate Sr-deficiency is an effective approach to enhance the ORR activity and stability of SOFC cathodes.