Elaboração e caracterização de La1-xSrxCoyFe1-yO3-d para catodo de pilhas a combustível de óxido sólido

Abstract

Due to the mixed conductivity (ionic and electronic) of Lanthanum Strontium Cobalt Iron Oxide (LSCF), its high electrical conductivity and its catalytic activity for oxygen reduction reaction, this material is presented suitable for application as cathode of Solid Oxide Fuel Cells with operation at intermediate temperatures (IT-SOFC). Considering this fact, the realized work aimed obtaining and study LSCF films byserigraphy for use as cathodes of Solid Oxide Fuel Cells. LSCF powders were synthesized by three different routes: Pechini, citrate and coprecipitation with two different compositions: La0.6Sr0.4Co0.2Fe0.8O3-d and La0.6Sr0.4Co0.8Fe0.2O3-d. The different powder samples were characterized by thermal analysis, X-ray diffraction, nitrogen adsorption (BET), dynamic light scattering, plasmaspectrometry, Mössbauer spectroscopy and dilatometry. From the powders, suspensions were obtained which were analyzed by thermal analysis and rheology. The deposition of the suspensions by screen printing resulted in films analyzed by optical microscopy and scanning electron microscopy. Later, the conductivities and power densities of the cells were evaluated by electrochemical measurements and byelectrochemical impedance spectroscopy (EIS). The results indicated that all routes used enabled the attainment of LSCF in its crystalline phase. It was observed that the citrate route gave rise to the most appropriate morphology of the powders and films as well as the highest conductivity. The La0.6Sr0.4Co0.8Fe0.2O3-d composition presented the greatest electrical conductivity. The cell produced with LSCF cathode and supported mechanically by anode of nickel oxide and yttria stabilized zirconia showed the highest potency obtained until now by the Laboratório de Materiais e Pilhas a Combustível de Óxido Sólido (LaMPaC)