Suppressing Sr segregation in SOFC cathodes via infiltration-driven cationic surface enrichment

Abstract Sr segregation is one of the critical degradation issues in perovskite cathode for solid oxide fuel cells (SOFCs), leading to the formation of insulating secondary phases that block active sites and accelerate performance decay. Conventional mitigation strategies rely on A-site deficiency to reduce the driving force for Sr migration, but this approach inevitably alters bulk stoichiometry and transport properties. Here, we demonstrate an opposite design concept: cationic surface enrichment via targeted metal infiltration . By selectively introducing Sr (a segregation-prone A-site cation), Sm (a non-Sr A-site cation), and Co (a B-site cation) into Sm 0.5 Sr 0.5 CoO 3− δ electrodes, we establish controlled compositional gradients at the electrode surface. Among these, Sm infiltration substantially enhanced initial electrochemical performance (2.51 W·cm −2 @850 °C) and showed the most stable long-term performance, effectively suppressing Sr surface segregation under accelerated durability tests under a 10% CO 2 –90% O 2 atmosphere. Comprehensive electrochemical impedance spectroscopy and distribution of relaxation times analyses reveal that Sm infiltration enhances surface exchange kinetics and limits degradation of gas adsorption, while XPS and Raman spectroscopy confirm reduced perovskite decomposition. This work establishes A-site cation enrichment surface with non-segregating cations as a general and contrasting strategy to conventional A-site deficiency, providing a new pathway to simultaneously improve performance and durability of SOFC cathodes.