EAM Seminar Catalytic Materials (Research Area D)
Catalytic Reactions Up Close-Oxidation Chemistry at
the Boundary of Au Nanoparticles Supported on TiO2
Professor John T. Yates, Jr.
Department of Chemistry,
University of Virginia, Charlottesville, VA, USA
Thursday, 20 October 2011, 16:30,
Lecture room H3, Egerlandstr. 3
The oxidation of both carbon monoxide[1] and hydrogen[2] has been investigated on
nanometer-sized Au particles supported on TiO2 at low temperatures. For CO
oxidation, the prevailing view is that the reaction occurs on Au sites at the Au/TiO 2
interface. In contrast, we observed the activity to be at dual catalytic sites at the
perimeter of 3-nanometer Au particles supported on TiO2. Infrared-kinetic
measurements indicate that O-O bond scission is activated by the formation of a COO2 complex at dual Ti-Au sites at the perimeter of the Au particles. Density functional
theory calculations, which provide the activation barriers for the formation and bond
scission within the CO-O2 complex, support this model as well as confirming the
measured apparent activation energy of 0.16 eV. The operation of dual sites at the Au
particle perimeter is supported by the observation that sequential delivery of CO
occurs to these sites, first from adsorbed CO diffusion across the TiO 2 surfaces
surrounding the Au particles, and then from CO diffusion across the surfaces of the
Au particles themselves to the perimeter sites. A similar model was developed from
studies of H2 activation on Au/TiO2 nanocatalysts. An O2-assisted H2 dissociation
process via a Ti-OOH intermediate at a perimeter site was proposed, involving an
early transition state. The calculated activation energies for sequential steps in the
range 0.13 – 0.25 eV agree well with the apparent activation energy of 0.22 eV for
hydrogen oxidation.
[1]. I.X. Green, W. Tang, M. Neurock and J. T. Yates, Jr., Science, 333, 736-739 (2011).
[2]. I.X. Green, W. Tang, M. Neurock and J.T. Yates, Jr., Angew. Chem. Int. Ed.
DOI:10.1002/anie.201101612
Work supported by the Department of Energy, Office of Basic Energy Sciences, under Grant
Number DE-FG02-09ER16080 as well as the NSF and the Texas Advanced Computing
Center for Teragrid resources.
Contact: Prof. Jörg Libuda | Institute of Physical Chemistry
Phone: 09131/85-27308 | Mail: [email protected]