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

Proton conducting ceramic cells enable efficient electrocatalytic H2-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 (Ba0.9Ce0.1-α)(CeαFe0.8Ni0.2-β)O3-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 cm2 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. Cation migration plays a critical role in the evolution of perovskite electrodes but is not fully understood. Here, the authors combine theory and experiment to show that cation migration coupled with phase segregation forms a highly active nanocomposite electrode.