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 Pr0.8Sr1.2(CuFe)(0.4)Mo0.2Mn0.2Nb0.2O4-delta (HE-PSCFMMN) layered perovskite uniformly coated with in situ exsolved core-shell structured CuFe alloy@FeOx (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 degrees 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 FeOx 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.