Electrochemical properties of La0.6Sr0.4Co1-xFex-0.03Ni0.03O3-d (x=0.2, 0.5, 0.8) synthesized by citric method as cathodes for IT-SOFCs

Metal substituted La0.6Sr0.4Co1-xFexO3-? (LSCF) is a promising candidate for IT-SOFC cathodes [1,2]. Besides the composition of based LSCF, the synthetic approach plays an important role in the cathodic performance by affecting physical and chemical properties of the materials [3]. Up to now, few researches focus on metal doped LSCF by sol-gel citric method. In our work, pure phase Ni doped B-site with compositions La0.6Sr0.4Co1-xFex-0.03Ni0.03O3-? (x=0.2, 0.5, 0.8) were successfully synthesized by citric method, as determined by XRD analysis and Rietveld refinement. The effects of the doping metal insertion were investigated by XPS, TGA, TPR and EXAFS analyses. XPS and TGA results showed that the oxygen vacancies are increased by Ni doping and the highest content was found in La0.6Sr0.4Co0.8Fe0.17Ni0.03O3-?. EXAFS analyses investigating the local environment of Ni showed that the Fe/Co content plays a key role in the insertion of Ni2+ inside the perovskite structure. The reduction properties of Co3+/Fe3+ species were also affected by Ni doping and by the Fe/Co content in the perovskite. In Figure 1, the Arrhenius plot of conductivities measured from impedance spectroscopy analyses carried out on La0.6Sr0.4Co1-xFex-0.03Ni0.03O3-? perovskites is shown. Tests were carried out by using a three-electrode cell supported on a CGO electrolyte. Generally, the addition of the perovskite-based Ni catalyst promotes the oxygen ion conductivity of about half order of magnitude with respect to the CGO electrolyte. Also the Ea is positively affected.