Suppressing cation segregation on lanthanum-based perovskite oxides to enhance the stability of solid oxide fuel cell cathodes

Abstract

The slow rate of oxygen reduction reaction (ORR) at the cathode side has been considered as a scientific challenge to improve the overall performance of solid oxide fuel cell (SOFC). Unfortunately, dopant cation enrichment on the surface of perovskite-type cathode materials often leads directly to the reduction in activity and stability of ORR. For this reason, we quantitatively assessed the main driving force of dopant segregation on LaBO₃(001) surfaces (B = Cr_0.50Mn_0.50, Mn, Fe, Co_0.25Fe_0.75, Co, and Ni) using density functional theory (DFT) calculations. Based on our findings, the minimization of elastic energy, which is closely related to the size of both A-site and B-site cations, plays an important role on the A-site dopant segregation. The degree of dopant segregation can be controlled by the proper choice of cations contained in LaBO₃-type perovskite oxides. We therefore suggest a valuable principle that can be applied to design high performance cathode materials by suppressing the dopant cation enrichment at the surface.