Evaluation of calcium doped Ba-Co-Nb-O perovskite as cathode materials for intermediate-temperature solid oxide fuel cells

Abstract

High-performance cathode materials are critical for the commercialization of solid oxide fuel cells (SOFCs). In this study, an isovalent doping strategy is developed to improve the electrocatalytic performance and stability of Ba_1-xCa_xCo_0.8Nb_0.2O_3-δ for the first time. Multiple experimental characterization results combing with the DFT calculations prove that Ca²⁺ doping effectively reduces the valence state of cobalt, and leads to a decrease in covalency between Co and O, therefore promotes the creation of oxygen vacancies. The best electrochemical performance is achieved in the material with Ca²⁺ doping concentration of x = 0.15. The cathode shows the smallest polarization resistance of 0.019 Ω cm² at 700 °C, and the single cell exhibits the maximum power density (MPD) of 780 mW cm⁻². Meanwhile, the stability and CO₂ tolerance properties are improved.