A medium entropy cathode with enhanced chromium resistance for solid oxide fuel cells

Perovskite type SrCo0.9Ta0.1O3-δ (SCT91) cathode exhibits high activity for oxygen reduction reactions, but the instability in Cr-containing atmosphere restricts its application in intermediate temperature solid oxide fuel cells (IT-SOFCs). In this study, a B-site medium-entropy SrCo0.5Fe0.2Ti0.1Ta0.1Nb0.1O3-δ (SCFTTN52111) cathode is proposed and investigated as a potential Cr-tolerance cathode. The electrochemical activity of pristine SCT91 cathode degrades rapidly in the presence of volatile chromium species. In contrast, SCFTTN52111 performs very stable. Chromium vapors prefer to react with segregated SrO species rather than Co3O4 precipitates. Significant secondary phases of SrCrO4 and Co3O4 are detected on SCT91 electrode, while only trace by-products are found on medium-entropy cathode. The better Cr tolerance is closely related to the enhanced structural stability by medium-entropy engineering and reduced surface Sr segregations. This work sheds light on the development of robust cathodes for IT-SOFCs through rational design of configuration entropy.