Ba-Deficient Cathodes with Enhanced ORR Activity and CO ₂ Tolerance for Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) offer a sustainable pathway for efficient energy conversion, but developing cathode materials that deliver high oxygen reduction reaction (ORR) activity and long-term stability under CO 2 -rich conditions remains a critical challenge. Herein, we design a series of Ba-deficient layered perovskites, PrBa 0.8− x Ca 0.2 Co 2 O 6− δ (PB0.8− x CC, x = 0, 0.05, 0.10), to achieve simultaneous enhancement in catalytic performance and CO 2 tolerance. Among them, PB0.75CC ( x = 0.05) exhibits markedly higher concentration of oxygen vacancies compared to the stoichiometric PB0.80CC, thereby promoting superior oxygen-ion transport. Density functional theory (DFT) calculations reveal that Ba deficiency lowers the oxygen vacancy formation energy in the Ba-O layers, facilitating the development of 3-dimensional oxygen-ion diffusion pathways and thereby accelerating ORR kinetics. When employed as a cathode in an oxygen-ion conducting SOFC, PB0.75CC shows excellent ORR performance, with a low polarization resistance ( R p ) of 0.022 Ω·cm 2 at 800 °C and a peak power density of 1.24 W/cm 2 at 800 °C. Moreover, DFT and Fourier-transform infrared spectroscopy analyses confirm weakened CO 2 adsorption and suppressed BaCO 3 formation, effectively mitigating CO 2 poisoning and enhancing cathode CO 2 tolerance. This study demonstrates an efficient defect-engineering approach to tailor structure–property relationship in layered perovskites, offering new insights into the design of high-performance, CO 2 -tolerant cathodes for next-generation SOFCs.