Novel high-entropy BaCo0.2Zn0.2Ga0.2Zr0.2Y0.2O3-δ cathode for proton ceramic fuel cells

The application of cobalt-based perovskite cathode materials in proton-conducting SOFCs (H–SOFCs) is challenged by their high thermal expansion coefficient (TEC). To address interface degradation/separation between the cobalt-based perovskite cathode and the proton-conducting electrolyte, we design and prepare the high-entropy perovskite oxide (HEPO) BaCo 0.2 Zn 0.2 Ga 0.2 Zr 0.2 Y 0.2 O 3-δ (BCX) as the cathode for proton-conducting SOFCs (H–SOFCs). BCX demonstrates remarkable performance and stability in the oxygen reduction reaction, validated through structural analysis and electrochemical characterizations. The TEC of BCX is as low as 12.75 × 10 -6  K −1 compared to the 18.69 × 10 -6  K −1 of the un-doped BaCoO 3-δ (BC). The polarization resistance of BCX cathode about 0.69 Ω cm 2 is realized at 600 °C, much lower than that for pristine BC cathode (1.27 Ω cm 2 ). Cell with BCX cathode exhibits remarkable long-term stability without detectable degradation over 100 h.