Synthesis and characterization of Sr 2 Fe 1.4 Ni 0.1 Mo 0.5-x Nb x O 6-δ ( x = 0, 0.05, 0.1, and 0.15) cathodes for solid oxide fuel cells

Nb modified Sr2Fe1.4Ni0.1Mo0.5-xNbxO6-δ (SFNi0.1MNbx, x = 0, 0.05, 0.1, and 0.15) materials are synthesized by the one-step combustion method, and their characteristics are investigated. According to the X-ray diffraction (XRD), all samples present single perovskite structures and scanning electron microscope (SEM) results indicate that all samples possess uniform porous structures. Additionally, the electrode conductivity is improved by doping Nb on the B′ site of SFNi0.1M. From the X-ray photoelectron spectroscopy (XPS) results, the ratios of Fe2+/Fe3+ and Mo6+/Mo5+ vary with the Nb content, which leads to the conductivity change of SFNi0.1MNbx materials. For all the samples, SFNi0.1MNb0.05 exhibits the best electrochemical performance with the lowest polarization resistance of 0.11 Ω cm2 and the highest power density of 1260 mW cm−2 800 °C in humidified H2. The results indicate that SFNi0.1MNbx is a promising type of candidate cathode for solid oxide fuel cells.