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

Solid oxide electrolysis cells (SOECs) are promising energy conversion devices capable of efficiently transforming CO₂ into CO, reducing CO₂ 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 CO₂ 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 CO₂ 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 CO₂ . 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 CO₂ adsorption, dissociation, and reduction.