UNIDEF   23986
UNIDAD DE INVESTIGACION Y DESARROLLO ESTRATEGICO PARA LA DEFENSA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
In situ XANES studies on Ce0.9Zr0.1-xSmxO2-x/2 (x= 0.1, 0.08, 0.06, 0.04, 0.02, 0) synthesized by hydrothermal method
Autor/es:
FERNANDO F. MUÑOZ; LUCÍA M. TOSCANI; ROSARIO SUAREZ ANZORENA; SUSANA A. LARRONDO
Lugar:
Campinas
Reunión:
Congreso; 30th RAU Annual Users Meeting LNLS/CNPEM; 2020
Institución organizadora:
CNPEM-LNLS
Resumen:
60%NiO/Ce0.9Zr0.1O2 has demonstrated to be an excellent anode material forIntermediate Temperature-Solid Oxide Fuel Cells. Nevertheless, its mixed conductivityshould be enhanced in reducing atmospheres [1]. The substitution of Zr4+ by Sm3+ isproposed to incorporate oxygen vacancies into the structure thus improving ionicconductivity. Ce0.9Zr0.1-xSmxO2-x/2 (x= 0.1, 0.08, 0.06, 0.04, 0.02, 0) mixed oxides weresynthesized via the hydrothermal method and calcined at 550 °C. X-ray diffraction withsynchrotron radiation shows that all samples are monophasic with the fluorite structure,typical of CeO2. Average crystallite sizes are nanometric (< 11 nm) and latticeparameters increases linearly with Sm3+ content. The effect of Sm3+ incorporation intothe lattice on redox properties was studied by in situ Dispersive X-ray absorptionspectroscopy (DXAS) experiments, performed in diluted H2 gas-flow (5 vol.% in50 mL.min-1, He balance), from room temperature to 800 ºC with a heating rate of10 ºC.min-1. DXAS measurements were performed at the Ce LIII absorption edge, beingthis spectroscopy especially suited for tracking time-dependent evolution of chemicalreactions. Three reduction steps were observed during the process, two of which can berelated to the reduction of surface Ce4+ species (< 600 °C) and the third one to thereduction of bulk species. The incorporation of Sm3+ increased the reduction kinetics ofbulk species. The exit gas is analyzed by online mass spectroscopy. Water productionwas observed in accordance with each reduction step.