Preparation and evaluation of Ca3−xBixCo4O9−δ (0< x ≤ 0.5) as novel cathodes for intermediate temperature-solid oxide fuel cells

The misfit compounds Ca3−xBixCo4O9−δ (x = 0.1–0.5) were successfully synthesized via conventional solid state reaction and evaluated as cathode materials for intermediate temperature-solid oxide fuel cells. The powders were characterized by X-ray diffraction, scanning emission microscopy, X-ray photoelectron spectroscopy, thermogravimetry analysis and oxygen-temperature programmed desorption. The monoclinic Ca3−xBixCo4O9−δ powders exhibit good thermal stability and chemical compatibility with Ce0.8Sm0.2O2−γ electrolyte. Among the investigated single-phase samples, Ca2.9Bi0.1Co4O9−δ shows the maximal conductivity of 655.9 S cm−1 and higher catalytic activity compared with other Ca3−xBixCo4O9−δ compositions. Ca2.9Bi0.1Co4O9−δ also shows the best cathodic performance and its cathode polarization resistance can be further decreased by incorporating 30 wt.% Ce0.8Sm0.2O2−γ. The maximal power densities of the NiO/Ce0.8Sm0.2O2−γ anode-supported button cells fabricated with the Ce0.8Sm0.2O2−γ electrolyte and Ca2.9Bi0.1Co4O9−δ + 30 wt.% Ce0.8Sm0.2O2−γ cathode reach 430 and 320 mW cm−2 at 700 and 650 °C respectively.