A highly oxygen reduction reaction active and CO₂ durable high-entropy cathode for solid oxide fuel cells

One big obstacle for the oxygen reduction reaction (ORR) electrode in solid oxide fuel cells (SOFCs) is the poor reaction activity and fast degradations caused by CO₂ poisoning. Here we report our design of an active A-site Ca-rich high-entropy Pr_0.1875Ba_0.1875Sr_0.1875La_0.1875Ca_0.25CoO_3-δ (PBSLC₂₅C) electrode, guided by the O p-band theory. When applied as a cathode in solid oxide fuel cells (SOFCs), it demonstrates high ORR activity and excellent CO₂ tolerance under realistic operating conditions. Ni-YSZ-based anode-supported cells with PBSLC₂₅C cathodes demonstrate excellent peak power densities of 1.14 W cm⁻², 1.04 W cm⁻², and 0.77 W cm⁻² in the air with 1%, 5%, and 10% CO₂, respectively, at 750 °C. The engineered high-entropy PBSLC₂₅C effectively diminishes the CO₂ poisoning effect and maintains active surfaces for fast oxygen exchange, as confirmed by the cell durability test in air containing CO₂ (5 and 10 vol%), Raman spectroscopy, and density functional theory calculations.