The effect of Mo and Sc dopants on the performance of an Sr2Fe2O6 cathode for use in proton-conducting solid oxide fuel cells

Abstract

Sr₂Fe₂O₆ was doped with Sc and Mo ions to investigate the effect of these dopants on the material properties and cathode performance. Both Sc and Mo were doped into Sr₂Fe₂O₆ as pure phases, and the thermal expansion coefficient (TEC) increased with the Sc content of the material. A first-principles calculation at the atomic level indicated that Mo facilitated hydration, whereas Sc doping facilitated the formation of oxygen vacancies. Simulation results showed that the lowest energy barrier to O₂ adsorption and dissociation was obtained by co-doping Sc and Mo into Sr₂Fe₂O₆, facilitating the cathode reaction. The results of fuel cell tests indicated that co-doping with Sc and Mo resulted in higher fuel-cell performance for Sr₂Fe₂O₆ than doping with Sc or Mo alone. An impedance analysis for Sr₂Fe₂O₆ co-doped with Sc and Mo indicated a good balance between hydration and oxygen vacancy formation, as well as a low energy barrier to O₂ adsorption and dissociation, which resulted in this material exhibiting the lowest polarization resistance among the tested cathodes. This study demonstrates that each dopant has unique advantages and disadvantages in terms of cathode properties, and it is necessary to strike a balance among the parameters involved to enhance the cathode performance.