Enhancing Cathode Performance of La 0.4 Sr 0.6 Fe 0.8 Co 0.2 O 3-δ -Based Perovskites through Lattice Distortion Induced by Entropy-Engineering

The entropy stabilization effect brought about by high configurational entropy enables the SOFC cathode to possess both excellent phase stability and electrochemical activity at high temperatures. In this study, two medium-entropy materials derived from La0.4Sr0.6Fe0.8Co0.2O3-δ are designed: La0.2Nd0.2Ca0.2Sr0.2Ba0.2Fe0.8Co0.2O3-δ and La0.2Sm0.2Ca0.2Sr0.2Ba0.2Fe0.8Co0.2O3-δ, and their performance as cathode materials for SOFCs is investigated. The results show that the entropy effect causes local lattice distortion, and the weakening of metal–oxygen bond promotes the formation of additional oxygen vacancies within the lattice, consequently enhancing the overall electrochemical performance of the oxide cathode. At 700 °C, the polarization resistance values are 0.082 Ω cm2 for La0.2Nd0.2Ca0.2Sr0.2Ba0.2Fe0.8Co0.2O3-δ and 0.059 Ω cm2 for La0.2Sm0.2Ca0.2Sr0.2Ba0.2Fe0.8Co0.2O3-δ respectively, significantly lower than that of La0.4Sr0.6Fe0.8Co0.2O3-δ (0.121 Ω cm2). Additionally, the anode supported fuel cell using a La0.2Sm0.2Ca0.2Sr0.2Ba0.2Fe0.8Co0.2O3-δ cathode operates stably at 0.5 V for 60 h, achieving a peak power density of 923 mW cm–2 at 700 °C.