Reports

Charging Effects on Bonding and Catalyzed Oxidation of CO on Au₈ Clusters on MgO

Bokwon Yoon,¹ Hannu Häkkinen,^1* Uzi Landman,¹ Anke S. Wörz,² Jean-Marie Antonietti,² Stéphane Abbet,² Ken Judai,² Ueli Heiz²

Gold octamers (Au₈) bound to oxygen-vacancy F-center defects on Mg(001) are the smallest clusters to catalyze the low-temperature oxidation of CO to CO₂, whereas clusters deposited on close-to-perfect magnesia surfaces remain chemically inert. Charging of the supported clusters plays a key role in promoting their chemical activity. Infrared measurements of the stretch vibration of CO adsorbed on mass-selected gold octamers soft-landed on MgO(001) with coadsorbed O₂ show a red shift on an F-center–rich surface with respect to the perfect surface. The experiments agree with quantum ab initio calculations that predict that a red shift of the C–O vibration should arise via electron back-donation to the CO antibonding orbital.

¹ School of Physics, Georgia Institute of Technology, Atlanta, GA 30332–0430, USA.
² Departement Chemie, Lehrstuhl für Physikalische Chemie I, Technische Universität München, Lichtenbergstraße 4, 85747 Garching, Germany.

^* Present address: Department of Physics, Nanoscience Center, Box 35, FIN-40014, University of Jyväskyla, Finland.

To whom correspondence should be addressed. E-mail: uzi.landman{at}physics.gatech.edu (U.L.); ulrich.heiz{at}ch.tum.de (U.H.)

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Mass Spectrometry Special Feature: Cluster reactivity experiments: Employing mass spectrometry to investigate the molecular level details of catalytic oxidation reactions.

G. E. Johnson, E. C. Tyo, and A. W. Castleman Jr. (2008)
PNAS 105, 18108-18113
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Identification of Active Gold Nanoclusters on Iron Oxide Supports for CO Oxidation.

A. A. Herzing, C. J. Kiely, A. F. Carley, P. Landon, and G. J. Hutchings (2008)
Science 321, 1331-1335
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Structures of Neutral Au7, Au19, and Au20 Clusters in the Gas Phase.

P. Gruene, D. M. Rayner, B. Redlich, A. F. G. van der Meer, J. T. Lyon, G. Meijer, and A. Fielicke (2008)
Science 321, 674-676
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Reactivity-promoting criterion based on internal vibrational energy redistribution.

R. Mitric, C. Brgel, and V. Bonaic-Koutecky (2007)
PNAS 104, 10314-10317
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Chemical Theory and Computation Special Feature: Materials by numbers: Computations as tools of discovery.

U. Landman (2005)
PNAS 102, 6671-6678
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