Hydrogen Interaction with a Ceria-Zirconia Supported Gold Catalyst. Influence of CO Co-adsorption and Pretreatment Conditions

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• 作者：Sebasti&aacute ; n E. Collins ; José ; M. Cí ; es ; Eloy del Rí ; o ; Miguel Ló ; pez-Haro ; Susana Trasobares ; José ; J. Calvino ; José ; M. Pintado ; Serafí ; n Bernal
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：October 4, 2007
• 年：2007
• 卷：111
• 期：39
• 页码：14371 - 14379
• 全文大小：303K
• 年卷期：v.111,no.39(October 4, 2007)
• ISSN：1932-7455

文摘

This work reports on the hydrogen interaction with a 3 wt % Au/Ce_0.62Zr_0.38O₂ (Au/CZ) catalyst prepared bydeposition-precipitation. As deduced from X-ray powder diffraction, electron microscopy (scanningtransmission electron microscopy-high-angle angular dark field and high-resolution electron microscopy),and CO volumetric/Fourier transform IR (FTIR) adsorption studies, the investigated catalyst shows a goodmetal dispersion. By combining FTIR spectroscopy and volumetric chemisorption studies, it is shown thatupon treating the Au/CZ catalyst with 40 Torr of H₂ at room temperature a fast and very intense spillovereffect occurs. As determined from the recorded isotherm, very high values of the apparent H/Au ratio (>8.0)and of the atomic hydrogen surface density (>11.0 H/nm²) are reached. In parallel with this observation, theonset of a characteristic IR band at 2133 cm^-1 shows the occurrence of significant support reduction withinherent appearance of Ce³⁺ species. Moreover, the simultaneous growth of the IR band at 1630 cm^-1 due tomolecular water strongly suggests that even at room temperature oxygen vacancies are also formed. AdditionalFTIR spectroscopy studies have shown that the hydrogen spillover is strongly inhibited by either co-adsorptionof CO or a reducing pretreatment with flowing 5% H₂/Ar at 673 K. These deactivation effects, however, maybe reverted by very mild regeneration treatments at room temperature.