Cation-Driven Charge Modulation and In-Situ Exsolved Nanoparticles Enable a Self-Assembled Cathode for Proton Ceramic Solid Oxide Cells
Protonic ceramic fuel cells (PCFCs) offer efficient intermediate-temperature energy conversion but are constrained by the trade-off between insufficient electrode activity and limited operational durability. This work develops a Zn/Yb B-site codoping strategy combined with temperature-induced nanoparticle exsolution to construct a triple-conducting cathode. Cation-driven charge modulation enhances ionic diffusion and electronic conduction, while the exsolved secondary BaCoO3−δ phase increases active site density, optimizes interfacial charge transfer, and promotes oxygen reduction reaction (ORR) kinetics. Zn/Yb codoping redistributes local charge density, weakens metal–oxygen bonds, and reduces oxygen vacancy formation energy, promoting oxygen vacancy generation. The increased oxygen vacancy concentration facilitates surface oxygen activation and lattice hydration, enhancing oxygen-ion and proton transport. Enhanced d–p orbital hybridization improves electronic conductivity and accelerates charge transfer kinetics. Optimized alkaline–earth sites suppress carbonate formation, imparting excellent CO2 tolerance. The optimized cathode delivers a peak power density of 0.99 W·cm−2 at 600 °C and stable operation over 100 h, with a polarization resistance of 0.110 Ω·cm2 under 20% H2O-air. This work provides a novel strategy for optimizing activity, conductivity, and stability in PCFC cathodes.