Strategic atomic trapping at heterointerfaces for protonic ceramic cells

Engineering dynamic heterointerfaces with atomic precision is critical for unlocking the full potential of reversible protonic ceramic electrochemical cells in sustainable energy conversion, while minimizing precious metal use in composite electrodes. Here, we introduce an atomic trapping strategy that restructures the interfacial chemistry of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ perovskite and Ru@CeO_2-δ fluorite heteroelectrodes, achieving catalytic synergy through manipulating Ru coordination environment. A scalable co-sintering protocol induces thermodynamically driven Ru migration from the CeO₂ lattice into the perovskite matrix, creating coupled interfaces. This optimizes interfacial electron redistribution, generates interfacial oxygen vacancies, and improves triple conductivity and hydration kinetics. The electrode with low Ru loading exhibits bifunctionality, delivering a peak power density of 1.51 W cm^-2 and an electrolysis current density of -2.21 A cm^-2 at 650 °C. It demonstrates notable durability with minimal degradation (0.09 mV h^-1) over 400 h at 600 °C, providing a universal strategy for next-generation solid-state energy devices.