A High‐Entropy Layered Perovskite Coated with In Situ Exsolved Core‐Shell CuFe@FeOx Nanoparticles for Efficient CO2 Electrolysis

Abstract Solid oxide electrolysis cells (SOECs) are promising energy conversion devices capable of efficiently transforming CO 2 into CO, reducing CO 2 emissions, and alleviating the greenhouse effect. However, the development of a suitable cathode material remains a critical challenge. Here a new SOEC cathode is reported for CO 2 electrolysis consisting of high‐entropy Pr 0.8 Sr 1.2 (CuFe) 0.4 Mo 0.2 Mn 0.2 Nb 0.2 O 4‐δ (HE‐PSCFMMN) layered perovskite uniformly coated with in situ exsolved core‐shell structured CuFe alloy@FeO x (CFA@FeO) nanoparticles. Single cells with the HE‐PSCFMMN‐CFA@FeO cathode exhibit a consistently high current density of 1.95 A cm −2 for CO 2 reduction at 1.5 V while maintaining excellent stability for up to 200 h under 0.75 A cm −2 at 800 °C in pure CO 2 . In situ X‐ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations confirm that the exsolution of CFA@FeO nanoparticles introduces additional oxygen vacancies within HE‐PSCFMMN substrate, acting as active reaction sites. More importantly, the abundant oxygen vacancies in FeO x shell, in contrast to conventional in situ exsolved nanoparticles, enable the extension of the triple‐phase boundary (TPB), thereby enhancing the kinetics of CO 2 adsorption, dissociation, and reduction.