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Abstract: The double perovskite Sr2CoMoO6−δ was investigated as a candidate anode for a solid oxide fuel cell (SOFC). Thermogravimetric analysis (TGA) and powder X-ray diffraction (XRD) showed that the cation array is retained to 800°C in H2 atmosphere with the introduction of a limited concentration of oxide–ion vacancies. Stoichiometric Sr2CoMoO6 has an antiferromagnetic Néel temperature T N ≈37K, but after reduction in H2 at 800°C for 10h, long-range magnetic order appears to set in above 300K. In H2, the electronic conductivity increases sharply with temperature in the interval 400°C< T <500°C due to the onset of a loss of oxygen to make Sr2CoMoO6−δ a good mixed oxide–ion/electronic conductor (MIEC). With a 300-μm-thick La0.8Sr0.12Ga0.83Mg0.17O2.815 (LSGM) as oxide–ion electrolyte and SrCo0.8Fe0.2O3−δ as the cathode, the Sr2CoMoO6−δ anode gave a maximum power density of 1017mWcm−2 in H2 and 634mWcm−2 in wet CH4. A degradation of power in CH4 was observed, which could be attributed to coke build up observed by energy dispersive spectroscopy (EDS). [ABSTRACT FROM AUTHOR]

Abstract: Double-perovskite Ba2MMoO6 (M=Fe, Co, Mn, Ni) has been systematically investigated as anode materials for solid oxide fuel cells (SOFCs). Among these materials, Ba2FeMoO6 shows the best electrochemical performance with maximum power density of 605mWcm−2 and electronic conductivity of 196Scm−1 at 850°C in H2. Thermal expansion coefficients of Ba2MMoO6 are distributed within the range of (10−18)×10−6 K−1, matching well with that of La0.8Sr0.2Ga0.83Mg0.17O3−δ electrolyte. Thermogravimetric analysis (TGA) clearly indicates that oxygen vacancies are formed in all the Ba2MMoO6 materials. For the Ba2MMoO6 anodes, the power output decreases in the order of M=Fe>M=Co>M=Mn>M=Ni; the overpotential increases in the order of M=Fe

Abstract: Layered perovskite PrBa0.5Sr0.5Co2−x Fe x O5+δ (PBSCF, x = 0.5, 1.0, 1.5) oxides are designed and evaluated as cathode materials for solid-oxide fuel cells. Effect of Fe/Co molar ratio on structural, thermal and electrochemical properties for PBSCF is systematically investigated. With increasing x from 0.5 to 1.5, the structure does not change but the lattice parameters increase. At the same time, thermal expansion coefficient decreases, which is helpful to thermally match with the electrolyte. From X-ray photoelectron spectra, it can be seen that both Fe and Co exist in a mixed oxidation state. Fe ions are prone to high oxidation state (Fe3+ and Fe4+), while Co ions basically exhibit low oxidation state (Co2+ and Co3+). The PBSCF samples exhibit a semiconductor–metal transition in the temperature range of 250–300 °C. With increasing Fe substitution content for Co, the electrode polarization resistance increases. The PBSCF (x = 0.5) cathode exhibits the highest power density of 697 mW cm−2 at 850 °C. The cell power output strongly depends on microstructure, electronic conductivity and electrochemical resistance. [Copyright &y& Elsevier]