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Abstract: The misfit compounds Ca3−x Bi x Co4O9−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−x Bi x Co4O9−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−x Bi x Co4O9−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. [Copyright &y& Elsevier]

Abstract: Zinc-doped barium strontium cobalt ferrite (Ba0.5Sr0.5Co0.2− xZnxFe0.8O3− δ (BSCZF), x = 0, 0.05, 0.1, 0.15, 0.2) powders with various proportions of zinc were prepared using the ethylenediamine tetraacetic acid (EDTA)-citrate method with repeated ball-milling and calcining. They were then evaluated as cathode materials for solid oxide fuel cells at intermediate temperatures (IT-SOFCs) using XRD, H2-TPR, SEM, and electrochemical tests. By varying the zinc doping (x) from zero to 0.2 (as a substitution for cobalt which ranged from zero to 100%), it was found that the lowest doping of 0.05 (BSCZF05) resulted in the highest electrical conductivity of 30.7 S cm−1 at 500 °C. The polarization resistances of BSCZF05 sintered at 950 °C were 0.15 Ω cm2, 0.28 Ω cm2 and 0.59 Ω cm2 at 700 °C, 650 °C and 600 °C, respectively. The resistance decreased further by about 30% when Sm0.2Ce0.8O2− δ (SDC) electrolyte particles were incorporated and the sintering temperature was increased to 1000 °C. Compared to BSCF without zinc, BSCZF experienced the lowest decrease in electrochemical properties when the sintering temperature was increased from 950 °C to 1000 °C. This decrease was due to an increase in thermal stability and a minimization in the loss of some cobalt cations without a decrease in the electrical conductivity. Using a composite cathode of BSCZF05 and 30 wt.% of SDC, button cells composed of an Ni-SDC support with a 30 μm dense SDC membrane exhibited a maximum power density of 605 mW cm−2 at 700 °C. [Copyright &y& Elsevier]