AVS 51st International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP36
Adsorption and Reaction of Oxygen and Hydrogen on Free Platinum Clusters

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: M. Andersson, Chalmers University of Technology and Goteborg University, Sweden
Authors: M. Andersson, Chalmers University of Technology and Goteborg University, Sweden
A. Rosen, Chalmers University of Technology and Goteborg University, Sweden
Correspondent: Click to Email
In a cluster beam experiment metal clusters are produced with a pulsed laser vaporization source, kept at room temperature or liquid nitrogen temperature. The beam of neutral clusters passes two low-pressure collision cells and clusters and reaction products are detected with laser ionization and time-of-flight mass spectrometry. Thus, the reaction probability in a cluster-molecule collision can be determined.@footnote 1@ Stable reaction products with O@sub 2@ are detected for clusters with more than 6 atoms, and a high and relatively size-independent reaction probability of about 0.3 is measured. Also H@sub 2@ adsorbs readily on Pt@sub n@ but the exact number of adsorbed molecules is difficult to determine because of the Pt isotope distribution. If the clusters first react with O@sub 2@ and then with H@sub 2@ one can observe that the reaction of Pt@sub n@(O@sub 2@)@sub m@ with H@sub 2@ results in the removal of oxygen atoms from the cluster. This is interpreted as formation of water molecules, which subsequently desorb. The efficiency of the catalytic water formation is high on all cluster sizes measured (7-30 atoms), with only a weak dependence on cluster size.@footnote 2@ The configuration with two separate reaction cells enables reversing the order of interaction with the reactant molecules, and a high reaction efficiency is measured also when the Pt clusters first interact with H@sub 2@. @FootnoteText@ @footnote 1@ M. Andersson, J.L. Persson, and A. Rosen, J. Phys. Chem. 100, 12222 (1996).@footnote 2@ M. Andersson and A. Rosen, J. Chem. Phys. 117, 7051 (2002). .