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Issue 22, 2003
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Interaction of NO with alumina supported palladium model catalysts

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Abstract

The interaction of NO with a well-defined supported Pd model catalyst has been investigated, employing a combination of IR reflection absorption spectroscopy (IRAS) and molecular beam methods. The model catalyst is based on an ordered Al2O3 film, grown on NiAl(110) and has been characterized in detail with respect to its geometric and electronic structure previously. In a first step the interaction of NO with the pure Al2O3 model support is studied. It is observed that NO slowly decomposes at low surface temperature (100 K), resulting in the formation of a variety of NxOy surface species. The decomposition process involves strong structural transformations of the Al2O3 film and is initiated at oxide defect sites. The adsorption of NO on the Pd/Al2O3 model system is explored systematically as a function of surface coverage and temperature. For NO adsorption on the Pd particles, characteristic absorption bands are identified by comparison with single crystal data, which are indicative of particle-specific sites such as edges and other defects. At 300 K and above NO dissociation occurs on the Pd particles, whereas the low-temperature decomposition channel on the alumina support is found to be strongly suppressed in the presence of the Pd particles. Finally, co-adsorption of NO with oxygen- and CO-precovered Pd particles is investigated. Preadsorbed oxygen results in the formation of a mixed adsorbate layer with an enhanced NO population of on-top sites on the particles. NO adsorption on a CO layer, on the other hand, gives rise to a compression of the CO layer and an enhanced population of on-top sites by CO.

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Article information


Submitted
08 Aug 2003
Accepted
16 Sep 2003
First published
15 Oct 2003

Phys. Chem. Chem. Phys., 2003,5, 5139-5148
Article type
Paper

Interaction of NO with alumina supported palladium model catalysts

S. Schauermann, V. Johánek, M. Laurin, J. Libuda and H. Freund, Phys. Chem. Chem. Phys., 2003, 5, 5139
DOI: 10.1039/B309490A

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