Fe-Based High-Entropy Perovskite Oxide: A Strategy to Suppress Sr Segregation and Performance Evaluation as an Electrode Material for SOFCs

The development of symmetrical solid oxide fuel cells (SSOFCs) has been restricted by the challenge of finding electrode materials that are both highly active and stable. Sr segregation on the surface of perovskite oxides can also significantly affect the durability and oxygen reduction activity of the SSOFC electrodes. In this study, the concept of high-entropy electrodes is proposed, and a high-entropy perovskite oxide La0.2Pr0.2Eu0.2Ce0.2Sr0.2FeO3−δ (HEP-LSF) was fabricated and examined as a favorable electrode material for SSOFCs. The catalytic activity and electrochemical performance were significantly improved by partial substitution of Eu, Pr, and Ce into the A-site, whereas the formation of a disorderly stress field around Sr suppressed Sr-segregation during long-term operation. The HEP-LSF cathode attained a remarkably low polarization resistance of 0.136 Ω·cm2 in yttria-stabilized zirconia (YSZ) at 800 °C, which is almost half (0.265 Ω·cm2) of a conventional La0.2Sr0.8FeO3−δ (LSF) cathode under the same conditions. The YSZ-based SSOFC with HEP-LSF electrodes exhibited a power density of 451 mW/cm2 at 800 °C. More importantly, the SSOFC with HEP-LSF electrodes exhibited good stability at 700 °C for 100 h. Moreover, the electrical conductivity and activation energy for HEP-LSF is higher than LSF which is 18.67 kJ·mol–1, and 599.57 S·cm–1 at 800 °C. These results demonstrate that HEP-LSF suppresses Sr segregation and has outstanding potential as an electrode material for SSOFC, thus making it a promising candidate for practical applications.