Fe-Based\nHigh-Entropy Perovskite Oxide: A Strategy\nto Suppress Sr Segregation and Performance Evaluation as an Electrode\nMaterial for SOFCs

The\ndevelopment of symmetrical solid oxide fuel cells (SSOFCs)\nhas been restricted by the challenge of finding electrode materials\nthat are both highly active and stable. Sr segregation on the surface\nof perovskite oxides can also significantly affect the durability\nand oxygen reduction activity of the SSOFC electrodes. In this study,\nthe concept of high-entropy electrodes is proposed, and a high-entropy\nperovskite oxide La<sub>0.2</sub>Pr<sub>0.2</sub>Eu<sub>0.2</sub>Ce<sub>0.2</sub>Sr<sub>0.2</sub>FeO<sub>3−δ</sub> (HEP-LSF)\nwas fabricated and examined as a favorable electrode material for\nSSOFCs. The catalytic activity and electrochemical performance were\nsignificantly improved by partial substitution of Eu, Pr, and Ce into\nthe A-site, whereas the formation of a disorderly stress field around\nSr suppressed Sr-segregation during long-term operation. The HEP-LSF\ncathode attained a remarkably low polarization resistance of 0.136\nΩ·cm<sup>2</sup> in yttria-stabilized zirconia (YSZ) at\n800 °C, which is almost half (0.265 Ω·cm<sup>2</sup>) of a conventional La<sub>0.2</sub>Sr<sub>0.8</sub>FeO<sub>3−δ</sub> (LSF) cathode under the same conditions. The YSZ-based SSOFC with\nHEP-LSF electrodes exhibited a power density of 451 mW/cm<sup>2</sup> at 800 °C. More importantly, the SSOFC with HEP-LSF electrodes\nexhibited good stability at 700 °C for 100 h. Moreover, the electrical\nconductivity and activation energy for HEP-LSF is higher than LSF\nwhich is 18.67 kJ·mol<sup>–1</sup>, and 599.57 S·cm<sup>–1</sup> at 800 °C. These results demonstrate that HEP-LSF\nsuppresses Sr segregation and has outstanding potential as an electrode\nmaterial for SSOFC, thus making it a promising candidate for practical\napplications.