UNIDEF   23986
UNIDAD DE INVESTIGACION Y DESARROLLO ESTRATEGICO PARA LA DEFENSA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Mesoporous zirconia based materials for catalysis and Solid Oxide Fuel Cells
Autor/es:
R. BACANI; D.G. LAMAS; T. MARTINS; MARCIA C. A. FANTINI; S.A. LARRONDO.
Lugar:
Dschang
Reunión:
Conferencia; First Pan African Conference on Crystallography; 2016
Resumen:
Mesoporous zirconia doped ceria (ZDC) solid-solutions are extensively used as promoters for three-way catalysts, which are applied in the control of NOx, CO and hydrocarbons emission from automotive exhausts. Since these materials are potential candidates for catalytic applications they also can be used as anodes in solid oxide fuel cells (SOFC), due to their excellent morphological and structural properties. The main goal is the enhancement on surface area, thermal stability and catalytic activity, aiming to achieve a lower working temperature (< 800 oC).In this work a new synthesis method was developed based on a template cooperative sol-gel process. Since high cerium oxide quantities lead to better catalytic performance, the ZDC were synthesized with 90%(mol) of ceria. NiO was impregnated into the ZDC matrix in order to obtain enough electronic conductivity for application as SOFC anodes.X-ray diffraction (XRD) results showed that these systems crystallized preferentially into cubic fluorite type structure together with smaller quantities of the tetragonal zirconia-ceria phase. Single phase ZDC was obtained for 90% of ceria after calcination at 400 ºC.Textural and morphological characteristics of samples calcined at 540 ºC were evaluated by N2 sorption, electronic microscopy images and small angle X-ray scattering (SAXS). The results revealed two-density (pores/particles) random distributed crystalline clusters of mesoporous ZrO2-CeO2, with homogeneous composition, average superficial area of 30-40 m²/g, high poli-disperse pores/particle sizes. Calcination up to 400 ºC presented a narrower pore size distribution and smaller pores, with higher superficial area (> 100 m²/g). The NiO particles formed an uniform layer over the ZrO2-CeO2.Catalytic activity for methane total oxidation reaction was similar for both calcination temperatures, showing 50% of CH4 conversion around 540 ºC.In situ absorption X-ray spectroscopy (XAS) experiments at Ni K-edge and Ce LIII-edge showed that all ceria contents are active for total and partial methane oxidation, CH4 decomposition and CO oxidation at 600 ºC.