Síntesis de conductores mixtos de Sm0.5Ba0.5CoO3-delta y caracterización como cátodos de celdas de combustible de óxido solido

Abstract

In the present work, the morphological, structural and electrical characteristics of nanostructured oxides of Sm_{0.5}Ba_{0.5}CoO_{3-δ} and Sm_{0.5}Ba_{0.5}CoO_{3-δ}- composites were studied. Ce_{0.8}Gd_{0.2}O_{1.9} to be used as possible candidates for intermediate temperature solid oxide fuel cells (IT-SOFC). For the preparation of the electrolyte, Nextech Materials powders were used, which were pressed uniaxially to achieve a high initial density, calcined at 1400°C, using a high-temperature oven located in the condensed matter laboratory of the University of Los Angeles. Andes and was sanded uniformly for due analysis. For the synthesis of the cathode, the mixtures of samarium, barium and cobalt nitrates were made, by means of the liquid mix method, with the obtained material the filtration and calcination process was carried out in order to obtain nanostructured powders, which were later They were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) and thus confirm if they presented the structural and morphological characteristics initially proposed, to meet the objectives of this work. In the structural characterization of the material, the Rietveld method was used, adjusting by the least squares method and obtaining quite satisfactory refinement results with respect to the synthesis method, these samples were passed through the scanning electron microscope, Quanta 200 of the National University , obtaining micrographs for SBCO450 and SBCO850 with an average diameter of 450 nm to 550 nm, defined in chapter III section 5. With the nanostructured cathodes obtained with adequate adhesion to the electrolyte, the polarization resistance was minimized, for this it was necessary to measure the resistance of the electrode in different preparation conditions by means of EIS, in a symmetrical cell configuration [cathode/electrolyte/cathode]. at temperatures between 500°C and $750°C. The resistance of the electrode as a function of temperature was determined and the performance of the cathode was correlated with its microstructure, evaluated by DRX and MEB. An activation energy value between 13.26 eV and 15.47eV was obtained, relating how fast the reaction occurs in the cell and thus following an equivalent PCR circuit with a Warburg Ws element, which describes mass transport and a double layer capacitances (layers with opposite polarity), for the description of charge transfer processes. At the end, the conclusions of the work carried out are detailed, thus analyzing the compatibility, operation and applicability of this sample as a possible candidate for solid oxide fuel cells at intermediate temperatures.