A SrCo0.9Ta0.1O3-δ derived medium-entropy cathode with superior CO2 poisoning tolerance for solid oxide fuel cells

Abstract

The development of highly efficient and robust cathodes is crucial for intermediate temperature solid oxide fuel cells (IT-SOFC). Perovskite type SrCo0.9Ta0.1O3-δ (SCT91) is a promising cathode but its instability against CO2 limits the practical application. In this work, a new medium-entropy SrCo0.5Fe0.2Ti0.1Ta0.1Nb0.1O3-δ (SCFTTN52111) cathode is designed and evaluated. The effect of configuration entropy on electrical conductivity, physical and electrochemical properties are studied in detail. The SCFTTN52111 cathode exhibits a lower polarization resistance of 0.033 Ω cm2 at 700 °C, superior to 0.040 Ω cm2 of SCT91 parent. The higher oxygen reduction activity is attributed to its larger surface exchange coefficient and smaller particle size. More importantly, SCFTTN52111 displays outstanding stability and high CO2 tolerance, due to a more negative value of average metal-oxygen bond energy and significantly reduced surface Sr segregation. Our study provides a feasible and effective entropy engineering approach to design high-active and durable cathode materials for SOFCs.