Structure-Activity Relationship in Nanostructured Copper-Ceria-Based Preferential CO Oxidation Catalysts

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• 作者：D. Gamarra ; G. Munuera ; A. B. Hungr&iacute ; a ; M. Fern&aacute ; ndez-Garc&iacute ; a ; J. C. Conesa ; P. A. Midgley ; X. Q. Wang ; J. C. Hanson ; J. A. Rodr&iacute ; guez ; A. Mart&iacute ; nez-Arias
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：July 26, 2007
• 年：2007
• 卷：111
• 期：29
• 页码：11026 - 11038
• 全文大小：868K
• 年卷期：v.111,no.29(July 26, 2007)
• ISSN：1932-7455

文摘

Two series of nanostructured oxidized copper-cerium catalysts with varying copper loadings, and prepared,respectively, by impregnation of ceria and by coprecipitation of the two components within reversemicroemulsions, have been characterized in detail at structural and electronic levels by X-ray diffraction(XRD), Raman spectroscopy, high-resolution electron microscopy (HREM), X-ray energy dispersivespectroscopy (XEDS), X-ray photoelectron spectroscopy (XPS) (including Ar⁺-sputtering), and X-ray absorptionfine structure (XAFS). These results have been correlated with analysis of their catalytic properties forpreferential oxidation of CO in a H₂-rich stream (CO-PROX), complemented by Operando-DRIFTS. A relevantdifference between the two series of catalysts concerns the nature of the support for the surface-dispersedcopper oxide entities, which is essentially ceria for the samples prepared by impregnation and a Ce-Cumixed oxide for those prepared by microemulsion-coprecipitation. The existence of copper segregation inthe form of copper oxide or copper-enriched Cu-Ce mixed oxides for the latter type of samples is uniquelyrevealed by nanoprobe XEDS and XPS Ar⁺-sputtering experiments. The CO oxidation activity under CO-PROX conditions is correlated to the degree of support-promoted reduction achieved by the dispersed copperoxide particles under reaction conditions. Nevertheless, catalysts which display higher CO oxidation activityare generally more efficient also for the undesired H₂ oxidation reaction. The balance between both reactionsresults in differences in the CO-PROX activity between the two series of catalysts which are examined onthe basis of the structural differences found.