The catalyst Pt(1 wt %)/Ce0.6Zr0.4O2 is studied by CO-temperature programmed reduction (CO-TPR), isothermaloxygen storage complete capacity (OSCC), X-ray absorption spectroscopy (XAS) at the Pt LIII edge, and insitu X-ray diffraction (in situ XRD), with the aim of elucidating the role of supported metal in CO oxidationby ceria-based three-way catalysts (TWC). The redox behavior of Pt(1 wt %)/Ce0.6Zr0.4O2 is compared to thatof bare ceria-zirconia. OSCC of redox-aged Pt/ceria-zirconia is twice that of bare ceria-zirconia, and themaximum of CO consumption occurs at a temperature about 300 K lower than redox-aged ceria-zirconia.XAS analysis allows one to evidence the formation of a platinum-cerium alloy in redox-aged samples andthe stability of the metal particles toward oxidation and sintering during high-temperature treatments. UnderCO flux at 773 K, bare ceria-zirconia shows a continuous drift of diffraction peaks toward smaller Braggangles, due to a progressive increase of Ce(III) content. Under the same treatment, the structural rearrangementof Pt-supported ceria-zirconia starts after an induction time and takes place with an abrupt change of thelattice constant. The experimental evidence points to the role of supported Pt in modifying the redox propertiesof ceria-zirconia with respect to the bare support. It is proposed that the much faster bulk reduction observedby in situ XRD for redox-aged Pt/ceria-zirconia can be attributed to an easier release of reacted CO2, producinga more effective turnover of reactants at the catalyst surface.
|Numero di pagine||9|
|Rivista||JOURNAL OF PHYSICAL CHEMISTRY. B, CONDENSED MATTER, MATERIALS, SURFACES, INTERFACES & BIOPHYSICAL|
|Stato di pubblicazione||Published - 2006|
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