Fluorine-Modified Cobalt-Based Perovskites as High-Performance Cathodes for Solid Oxide Electrochemical Cells

This study introduces a novel strategy for enhancing the performance of SrCo0.9Ta0.1O3 (SCT) perovskite oxides as cathodes by disrupting the periodic arrangement of lattice oxygen through anionic fluorine doping. The partial substitution of oxygen with F in SrCo0.9Ta0.1O3–xFx (SCTFx) generates oxygen vacancies to maintain charge neutrality. Comprehensive characterizations revealed that F doping weakens the metal–oxygen bond strength, promoting oxygen release from the lattice. This, in turn, significantly increases oxygen mobility and enhances surface adsorption/dissociation kinetics, ultimately boosting the electrochemical performance. Among the investigated compositions, SCTF2 (x = 0.2) exhibited the best oxygen reduction reaction (ORR) activity, characterized by a minimal polarization resistance (Rp) of 0.029 Ω cm2 and a peak power density (PPD) of 0.93 W cm–2 at 800 °C. Beyond the ORR performance, F doping also conferred improved chemical stability, effectively suppressing Sr segregation under CO2-containing atmospheres, a critical factor for long-term operation. The SCTF2 material also demonstrates exceptional CO2 electrolysis performance, achieving a current density of 2.21 A cm–2 at 1.5 V and 800 °C, exceeding the performance of many reported solid oxide electrolysis cells (SOECs). These findings underscore the effectiveness of F doping as a means of manipulating the electrochemical catalytic activity and stability of perovskite cathodes, offering a viable pathway toward the development of advanced solid oxide fuel cell and electrolysis cell technologies.