Modulating Metal‐Oxygen Bonds in BaCo _0.4 Fe _0.4 Zr _0.1 Y _0.1 O _3‐δ to Enhance Oxygen Adsorption and Proton Conduction for High‐Performance Protonic Ceramic Fuel Cell Air Electrodes

ABSTRACT Protonic ceramic fuel cells (PCFCs) offer an efficient and low‐emission power generation technology. The air electrode critically governs the oxygen reduction reaction (ORR) kinetics and overall cell efficiency of PCFCs. BaCo _0.4 Fe _0.4 Zr _0.1 Y _0.1 O _3‐δ (BCFZY) perovskite, a triple‐conducting (H ⁺ /O ²⁻ /e ⁻ ) air electrode material, enables superior ORR kinetics in PCFCs, yet its performance is limited by insufficient ionic conductivity. Here, we develop BaCo _0.4 Fe _0.4‐x Zn _x Zr _0.1 Y _0.1 O _3‐δ (BCFZYZnx, x = 0, 0.1, 0.2) air electrodes via controlled Zn‐for‐Fe substitution to tailor metal‐oxygen bonding. Experimental and theoretical analyses reveal that this chemical modification optimizes the electronic structure and enhances surface alkalinity, facilitating hydration and proton conduction. The PCFC incorporating BCFZYZn0.2 air electrode achieves a peak power density of 0.510 W cm ⁻² at 650°C—36% higher than pristine BCFZY—along with stable operation over 100 h. This study offers a simple and effective strategy for designing highly active and durable air electrodes for efficient oxygen reduction.