Hydrogen-Promoted Oxygen Activation by Free Gold Cluster Cations.
Small gas-phase gold cluster cations are essentially inert toward molecular oxygen. Preadsorption of molecular hydrogen, however, is found to cooperatively activate the binding of O to even-size AU (x = 2, 4, 6) clusters. Measured temperature- and reaction-time-dependent ion intensities, obtained by...
| Published in: | Journal of the American Chemical Society Vol. 131; no. 25; pp. 8939 - 8952 |
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| Main Authors: | , , , , |
| Format: | Article |
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American Chemical Society
7/1/2009
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| Subjects: | |
| Online Access: | View this record in EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=43417405&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 43417405 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 7/1/2009 vid: 131 iid: 25 pid: 997 pub: American Chemical Society artinfo: ui: 43417405 10.1021/ja9022368 ppf: 8939 ppct: 13 formats: tig: atl: Hydrogen-Promoted Oxygen Activation by Free Gold Cluster Cations. aug: au: Lang, Sandra M. Bernhardt, Thorsten M. Barnett, Robert N. Bokwon Yoon Landman, Uzi affil: Institute for Surface Chemistry and Catalysis, University of Ulm, Albert-Einstein-A/lee 47, 89069 Ulm, Germany School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430 su: Ion traps Density functionals Molecular structure Mass spectrometry Hydrogen analysis Oxygen Charge transfer sug: subj: Ion traps Density functionals Molecular structure Mass spectrometry Hydrogen analysis Oxygen Charge transfer ab: Small gas-phase gold cluster cations are essentially inert toward molecular oxygen. Preadsorption of molecular hydrogen, however, is found to cooperatively activate the binding of O to even-size AU (x = 2, 4, 6) clusters. Measured temperature- and reaction-time-dependent ion intensities, obtained by ion trap mass spectrometry; in conjunction with first-principles density-functional theory calculations, reveal promotion and activation of molecular oxygen by preadsorbed hydrogen. These processes lead to the formation of a hydroperoxo intermediate on Au and Au and culminate in the dissociation of O via the release of HO. Langmuir-Hinshelwood reaction mechanisms involving the coadsorption of both of the reactant molecules are discussed for both cluster sizes, and an alternative Eley-Rideal mechanism involving hydrogen molecules adsorbed on a Au cluster reacting with an impinging gaseous oxygen molecule is analyzed. Structural fluctionality of the gold hexamer cation, induced by the adsorption of hydrogen molecules, and resulting in structural isomerization from a ground-state triangular structure to an incomplete hexagonal one, is theoretically predicted. Bonding of H on cationic gold clusters is shown to involve charge transfer to the clusters. This serves to promote the bonding of coadsorbed oxygen through occupation of the antibonding 2π* orbitals, resulting in excess electronic charge accumuiation on the adsorbed molecule and weakening of the O-O bond. The theoretical results for hydrogen saturation coverages and reaction characteristics between the coadsorbed hydrogen and oxygen molecules are found to agree with the experimental findings. The joint investigations provide insights regarding hydrogen and oxygen cooperative adsorption effects and consequent reaction mechanisms. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2009 holdings: @attributes: islocal: N |
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