Structural study of Ce0.9Zr0.1O2 nanocatalysts under redox conditions

M.G. ZIMICZ; F. PRADO; D.G. LAMAS; S. LARRONDO

Campinas

Congreso; 24° Reunion anual de usuarios del laboratorio Nacional de Luz Sincrotron; 2014

The aim of this work is to achieve a better understanding of the structural changes experienced by ZrO2-CeO2 mixed oxides under reducing and oxidizing conditions. Two samples, with Ce0.9Zr0.1O2 nominal composition, were studied. One of them with low surface area and the other with high surface area (samples LS and GS respectively). In-situ X-ray powder diffraction (XPD) experiments using synchrotron radiation were performed in different atmospheres (5 mol%H2/He, 5 mol% O2/He, and 2mol% CH4-4mol% O2 He balance) in the r.t to 900°C temperature range. XPD patterns were collected at the D10B-XPD beam-line of the Brazilian Synchrotron Light Laboratory (LNLS, Campinas, Brazil) using a high-intensity and low-resolution configuration, without crystal analyzer. The energy was set at 7997.43 eV and the X-ray wavelength was 1.55031 Å. Sample LS did not show any structural change under the studied conditions. On the contrary sample GS showed cubic fluorite structure until 870°C, with a segregation of a new phase for temperatures up to 900°C. After the reoxidation treatments in 5mol% O2 this segregated phase disappeared at 750°C, recomposing the original cubic structure. Finally, during in-situ XPD studies in 2 mol%CH4-4 mol%O2 atmosphere, GS XPD pattern revealed a new peak centered at 26.5°, which appears at 450°C and could be assigned to graphitic carbon formed during methane oxidation.