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dc.contributor.authorAllian, Ayman Daoud
dc.contributor.authorTakanabe, Kazuhiro
dc.contributor.authorFujdala, Kyle L.
dc.contributor.authorHao, Xianghong
dc.contributor.authorTruex., Timothy J.
dc.contributor.authorCai, Juan
dc.contributor.authorBuda, Corneliu
dc.contributor.authorNeurock, Matthew
dc.contributor.authorIglesia, Enrique
dc.date.accessioned2015-08-03T09:03:28Z
dc.date.available2015-08-03T09:03:28Z
dc.date.issued2011-03-30
dc.identifier.citationAllian, A. D., Takanabe, K., Fujdala, K. L., Hao, X., Truex, T. J., Cai, J., … Iglesia, E. (2011). Chemisorption of CO and Mechanism of CO Oxidation on Supported Platinum Nanoclusters. Journal of the American Chemical Society, 133(12), 4498–4517. doi:10.1021/ja110073u
dc.identifier.issn00027863
dc.identifier.pmid21366255
dc.identifier.doi10.1021/ja110073u
dc.identifier.urihttp://hdl.handle.net/10754/561737
dc.description.abstractKinetic, isotopic, and infrared studies on well-defined dispersed Pt clusters are combined here with first-principle theoretical methods on model cluster surfaces to probe the mechanism and structural requirements for CO oxidation catalysis at conditions typical of its industrial practice. CO oxidation turnover rates and the dynamics and thermodynamics of adsorption-desorption processes on cluster surfaces saturated with chemisorbed CO were measured on 1-20 nm Pt clusters under conditions of strict kinetic control. Turnover rates are proportional to O2 pressure and inversely proportional to CO pressure, consistent with kinetically relevant irreversible O2 activation steps on vacant sites present within saturated CO monolayers. These conclusions are consistent with the lack of isotopic scrambling in C16O-18O2-16O 2 reactions, and with infrared bands for chemisorbed CO that did not change within a CO pressure range that strongly influenced CO oxidation turnover rates. Density functional theory estimates of rate and equilibrium constants show that the kinetically relevant O2 activation steps involve direct O2* (or O2) reactions with CO* to form reactive O*-O-C*=O intermediates that decompose to form CO 2 and chemisorbed O*, instead of unassisted activation steps involving molecular adsorption and subsequent dissociation of O2. These CO-assisted O2 dissociation pathways avoid the higher barriers imposed by the spin-forbidden transitions required for unassisted O2 dissociation on surfaces saturated with chemisorbed CO. Measured rate parameters for CO oxidation were independent of Pt cluster size; these parameters depend on the ratio of rate constants for O2 reactions with CO* and CO adsorption equilibrium constants, which reflect the respective activation barriers and reaction enthalpies for these two steps. Infrared spectra during isotopic displacement and thermal desorption with 12CO- 13CO mixtures showed that the binding, dynamics, and thermodynamics of CO chemisorbed at saturation coverages do not depend on Pt cluster size in a range that strongly affects the coordination of Pt atoms exposed at cluster surfaces. These data and their theoretical and mechanistic interpretations indicate that the remarkable structure insensitivity observed for CO oxidation reactions reflects average CO binding properties that are essentially independent of cluster size. Theoretical estimates of rate and equilibrium constants for surface reactions and CO adsorption show that both parameters increase as the coordination of exposed Pt atoms decreases in Pt201 cluster surfaces; such compensation dampens but does not eliminate coordination and cluster size effects on measured rate constants. The structural features and intrinsic non-uniformity of cluster surfaces weaken when CO forms saturated monolayers on such surfaces, apparently because surfaces and adsorbates restructure to balance CO surface binding and CO-CO interaction energies. © 2011 American Chemical Society.
dc.publisherAmerican Chemical Society (ACS)
dc.titleChemisorption of CO and mechanism of CO oxidation on supported platinum nanoclusters
dc.typeArticle
dc.contributor.departmentBiological and Environmental Sciences and Engineering (BESE) Division
dc.contributor.departmentCatalysis for Energy Conversion (CatEC)
dc.contributor.departmentChemical Science Program
dc.contributor.departmentKAUST Catalysis Center (KCC)
dc.contributor.departmentPhysical Science and Engineering (PSE) Division
dc.identifier.journalJournal of the American Chemical Society
dc.contributor.institutionDepartment of Chemical Engineering, University of California, Berkeley, CA 94720, United States
dc.contributor.institutionNanostellar, Inc., 3696 Haven Avenue, Redwood City, CA 94063, United States
dc.contributor.institutionDepartments of Chemical Engineering and Chemistry, University of Virginia, Charlottesville, VA 22904, United States
dc.contributor.institutionDivision of Chemical Sciences, E. O. Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
dc.contributor.institutionGlobal Pharmaceutical Research and Development, Abbott Laboratories, 1401 Sheridan Rd., North Chicago, IL 60064, United States
dc.contributor.institutionPrecursor Energetics, 3221 Scott Blvd., Santa Clara, CA 95054, United States
dc.contributor.institutionAlternative Energy Products, Applied Materials, 3340 Scott Blvd., Santa Clara, CA 95052, United States
kaust.personTakanabe, Kazuhiro


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