Vacancy–Redox Coupling at Interface‐Engineered Heterostructures Enhances Reversible Energy Conversion in Protonic Ceramic Cells

at 1.3 V in electrolysis at 600°C, maintains >92% Faradaic efficiency, and shows minimal degradation over 200 h. Our results establish a general strategy for coupling hierarchical transport with chemically active, redox-buffered interphases to achieve both high kinetics and durability in protonic electrochemical systems.