Redox properties and catalytic performance for methane oxidation of NiO/Ce(1-x)M(x)O(2-d) (M= Gd, Sm, Y, Zr) nanocomposites: in-situ DXAS studies

TOSCANI L.M.; M.C.A. FANTINI; MARINA BELLORA; CRISTIÁN H. IRIART; D.G. LAMAS; M.G. ZIMICZ; LARRONDO S.A.

Campinas

Congreso; 29th Annual Users? Meeting LNLS/CNPEM; 2019

LNLS/CNPEM

CeO2-based materials have received great attention due to their excellent catalytic properties for oxidation reactions. The incorporation of a metal oxide in the CeO2 lattice can modify the oxygen storage capacity, ionic conductivity and specific surface area of these catalysts, so a wide variety of materials and applications are currently under investigation. In the field of new anodic materials for IT-SOFCs, CeO2-based anodes are subject of intense study because they have proven to exhibit excellent performance, not only in hydrogen-fueled SOFCs, but also operating with hydrocarbons. These excellent properties of CeO2-based anodes are probably related to the fact that they are mixed ionic/electronic conductors (MIECs) under reducing atmosphere and, therefore, fuel oxidation can take place on its entire surface, while its only occurs in the (anode/electrolyte/gas) interface (triple-phase boundaries) for electronic conductors. It is important to point out that the number of active points for fuel oxidation are dramatically increased in nanostructured, high specific surface area MIECs.In this work, we will compare the redoc properties and the catalytic performance for methane oxidation of several CeO2-based nanopowders and NiO/CeO2-based nanocomposites, treated at different temperatures in order to get materials with different average crystallite sizes. We performed dispersive X-Ray absorption spectroscopy (DXAS) studies at the D06B-DXAS beamline of the Brazilian Synchrotron Light Laboratory (LNLS, Brazil) on ZrO2, Gd2O3, Sm2O3, or Y2O3-doped CeO2 nanopowders (ZDC, GDC, SDC and YDC, respectively) and also NiO/ZDC, NiO/GDC, NiO/SDC amd NiO/YDC nanocomposites under different atmospheres and reaction conditions. We found that CeO2-based materials with small average crystallite size an dhigh specific surface area exhibit the best redox properties, while tha catalytic performance for methane oxidation depends on the dopant used in the CeO2-based phase.