Cation-Driven Charge Modulation and In-Situ Exsolved Nanoparticles Enable a Self-Assembled Cathode for Proton Ceramic Solid Oxide Cells

• • Peak power density of 0.99 W·cm−2 at 600 °C with BZCYYb electrolyte and stable operation over 100 h at 0.6 A·cm−2; this exceeds typical PCFC cathode performance by ~30–50%, enabling compact stack design and reduced material costs for intermediate-temperature operation. • • Area-specific resistance (ASR) of 0.166 Ω·cm2 in 3% H2O-air decreases to 0.110 Ω·cm2 in 20% H2O-air at 600 °C; the 34% reduction under humidified conditions demonstrates enhanced proton transport and surface exchange, critical for practical operation with reformed fuels. • • Zn/Yb codoping reduces oxygen vacancy formation energy and migration barriers, as confirmed by DFT; this increases oxygen vacancy concentration and enhances d–p orbital hybridization, yielding electronic conductivity improvements that lower ohmic losses and improve charge transfer kinetics. • • Optimized alkaline–earth sites suppress carbonate formation, providing excellent CO2 tolerance; this addresses a major degradation pathway in PCFCs, potentially extending operational lifetime in carbon-containing atmospheres and reducing the need for costly CO2 scrubbing.