ABSTRACT The performance of protonic ceramic fuel cells (PCFCs) is critically dependent on the surface architecture of cathode materials, yet direct observation of their dynamic evolution under operating conditions remains a formidable challenge. Herein, we employ operando Raman spectroscopy to track, in real‐time, the surface reconstruction of a tailored Ba 0.5 Sr 0.5 Co 0.9 Y 0.1 O 3 − δ (BSCY) perovskite cathode. Our results directly capture the exsolution of a BaCoO 3 − δ (BCO) secondary phase, which is induced by current and vapor, a process that can be precisely controlled and peaks within 20 min. By combining operando spectroscopic insights with density functional theory calculations, we decipher the synergistic mechanism: the surface‐reconstructed BCO phase significantly enhances oxygen adsorption, and the BSCY favors dissociation and product desorption. This coupling delivers remarkable electrochemical performance, achieving a peak power density of 1170 mW cm −2 at 650°C. This work not only establishes an operando characterization platform for visualizing electrode surface dynamics but also provides foundational insights into designing next‐generation PCFC cathodes through targeted surface engineering.
Li et al. (Mon,) studied this question.