Atomic‐to‐Nanoscale Cerium Engineering Enables Synergistic Dual‐Phase Electrodes for High‐Performance Reversible Protonic Ceramic Cells

Developing air electrodes that reconcile thermal stability with rapid oxygen kinetics remains a pivotal challenge for reversible protonic ceramic cells. Conventional cobalt‐based perovskites (e.g., BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3‐δ ) are plagued by high thermal expansion coefficients and insufficient oxygen vacancy concentrations. Here, a transformative material design strategy is demonstrated: through one‐pot synthesis, atomic‐scale cerium doping into the BCFZY lattice is simultaneously achieved along with the precipitation of nanoscale CeO 2 , creating a BCFZYC‐CeO 2 dual‐phase electrode. This approach synergistically resolves multiple limitations: atomic Ce doping modulates Co/Fe valence states to elevate oxygen vacancy density by 10%, while formed CeO 2 nanoparticles establish highly active interfaces that accelerate surface oxygen exchange kinetics and suppress TEC by 8.2%. Consequently, the electrode delivers a peak power density of 1.15 W·cm −2 at 650 °C in fuel cell mode and an electrolysis current density of −1.47 A·cm −2 at 1.3 V‐surpassing most previously reported modified BCFZY electrodes. The work establishes multiscale cerium engineering as a paradigm for next‐generation proton‐conducting energy devices, unifying catalytic enhancement with interfacial stability.