Coke formation during high-temperature CO2 electrolysis over AFeO3 (A\u202f=\u202fLa/Sr) cathode: Effect of A-site metal segregation

Abstract

Abstract In this study, strontium-doped lanthanum ferrite perovskite oxides (LSF) with different A-site occupancies were used as cathode catalysts for CO2 electrolysis at 800\u202f°C. XRD, EXAFS, XPS, FTIR, and temperature-programmed desorption were used to characterize the properties of the material. Fe K-edge EXAFS indicated that oxygen vacancy concentration and oxidation states of Fe atoms increased with concomitant improvement of electronic and ionic conductivities with a decrease in the A-site occupancy. XPS spectra revealed that Sr atoms segregated on the surface of A-site excess LSF92 to a greater degree than that on the A-site deficient LSF72. These segregated A-site metal oxides, especially SrO, are alkaline in nature and hence strongly bind to acidic CO2 forming stable SrCO3, which consequently facilitates carbon formation. This study highlights the effect of A-site stoichiometric modulation on carbon formation during electrolysis of CO2, which is crucial for improving the long- term performance of an SOEC.