B‒site-ordered Co-based double perovskites Sr2Co1−xNbxFeO5+δ as active and stable cathodes for intermediate-temperature solid oxide fuel cells

Abstract Highly active and stable cathodes for oxygen reduction reaction (ORR) are vital to develop intermediate-temperature solid oxide fuel cells (IT-SOFCs). Here we report a novel class of cathodes with B-site-ordered Co-based double perovskites Sr2Co1−xNbxFeO5+δ (SCNxF, x = 0.0–0.2). The SCNxF oxides have a single-phase cubic structure and good structural stability and chemical compatibility with La0.9Sr0.1Ga0.8Mg0.2O3–δ (LSGM) and Ce0.8Sm0.2O1.9 electrolytes. The Nb doping improves the thermodynamical stability and the thermal expansion compatibility of the SCNxF materials as compared to the undoped Sr2CoFeO5+δ. The area specific resistances of SCNxF cathodes with x = 0.0, 0.1, and 0.2 on the LSGM electrolyte are 0.048, 0.081, and 0.174 Ω cm2 at 700 °C, respectively. Also the SCN0.1F cathode shows better cell performance and electrochemical stability in the practical SOFC. The findings indicate that the SCN0.1F is a promising cathode material of IT-SOFCs with high electrocatalytic activity for ORR, functional stability, and high electrical conductivity.