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 Pr0.1875Ba0.1875Sr0.1875La0.1875Ca0.25CoO3-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 oC. 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.