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

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 = Cr0.50Mn0.50, Mn, Fe, Co0.25Fe0.75, 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.