Coupling cation migration with segregation for versatile air electrode in proton-conducting ceramic cells

Proton conducting ceramic cells enable efficient electrocatalytic H 2 -to-power conversion, yet their perovskite air electrodes demand versatile properties: high bulk proton uptake/conductivity, fast surface oxygen kinetics, and operational stability. Conventional single-phase perovskites usually fail to meet these demands simultaneously. Here, we show a facile strategy that couples bulk cation migration with surface segregation to enhance the versatility of the air electrode. The as-prepared (Ba 0.9 Ce 0.1-α )(Ce α Fe 0.8 Ni 0.2-β )O 3-δ -βNiO (cm-BCFN@NiO) electrode features a coupled bulk–surface architecture where finely dispersed NiO nanoparticles and Ce migration from A-sites to B-sites synergistically optimize surface oxygen kinetics, bulk proton uptake/conductivity, and electronic transport. The optimized electrode exhibits a low area-specific resistance of 0.3 Ω cm 2 at 550 °C—a 75% reduction compared to the NiO-free counterpart—enabling a 77.1% increase in maximum power density and over 1200 hours of stable single-cell operation. Beyond protonic ceramic cells, this work presents an approach for designing perovskites by leveraging cation migration and surface segregation at the atomic scale, opening more opportunities for a wide range of electrocatalytic applications.