Fluoride-driven modulation of oxygen vacancies and surface stability in cobalt-based perovskite as a high-performance cathode for solid oxide fuel cells

Abstract

Cathode materials with high catalytic performance and CO2 tolerance are essential for advancing the large-scale commercialization of solid oxide fuel cells (SOFCs). This study systematically investigates the impact of fluoride incorporation on the physical characteristics and electrochemical behavior of Pr0.4Sr0.6CoO3-δ (PSC) perovskite cathode. The results demonstrate that fluoride incorporation significantly decreases the coefficient of thermal expansion, thereby improving the thermal matching between the cathode and electrolyte materials. Additionally, the introduction of fluoride promotes the formation of oxygen vacancies, which facilitates the oxygen adsorption and dissociation processes, thereby improving the oxygen reduction reaction (ORR) kinetics. Furthermore, fluoride incorporation improves the chemical stability of the material by reducing the surface segregation of Sr, thereby greatly enhancing its CO2 tolerance. The results reveal that fluoride incorporation markedly lowers the polarization resistance (Rp) and improves ORR catalytic activity and output performance. At 800 ℃, fluoride incorporation reduces the Rp from 0.053 to 0.031 Ω cm2, representing a reduction of 41.5 %, while increasing the maximum power density to 1.18 W cm−2, which is 42.7 % higher than that of the undoped PSC. These findings indicate that fluoride incorporation is an effective strategy for significantly enhancing the electrochemical performance and stability of cobalt-based perovskites, providing a promising approach for the development of high-performance cathodes for SOFCs.