Molecular beam study of the catalytic oxidation of CO on a Pt(111) surface

Journal Article · Mon Dec 01 04:00:00 EST 1980 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.440029· OSTI ID:6789690

Campbell, C T; Ertl, G; Kuipers, H; Segner, J

The oxidation of carbon monoxide catalyzed by Pt(111) was studied in ultrahigh vacuum using reactive molecular beam--surface scattering. Under all conditions studied, the reaction follows a Langmuir--Hinshelwood mechanism: the combination of a chemisorbed CO molecule and an oxygen adatom. When both reactants are at low coverage, the reaction proceeds with an activation energy E(/sub LH/ =24.1 kcal/mole and a pre-exponential upsilon/sub 4/ =0.11 cm/sup 2/ particles/sup -1/ sec/sup -1/. At very high oxygen coverage, E(/sub LH/ decreases to about 11.7 kcal/mole and upsilon/sub 4/ to about 2 x 10/sup -6/ cm/sup 2/ particles/sup -1/ sec/sup -1/. This is largely attributed to the corresponding increase in the energy of the adsorbed reactants. When a CO molecule incident from the gas phase strikes the surface presaturated with oxygen, it enters a weakly held precursor state to chemisorption. Desorption from this state causes a decrease in chemisorption probability with temperature. Once chemisorbed, the CO molecule then has almost unit probability of reacting to produce CO/sub 2/ below 540 K. The CO/sub 2/ product angular distribution varies from cos..gamma.. to cos/sup 4/..gamma.. depending sensitively upon the adsorbed reactant concentrations.

• Research Organization: Institut fuer Physikalische Chemie, Universitaet Muenchen, Sophienstrasse 11, 8000 Muenchen 2, West Germany
• OSTI ID: 6789690
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 73:11; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640301* -- Atomic
Molecular & Chemical Physics-- Beams & their Reactions
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BEAMS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYSIS
CHALCOGENIDES
CHEMICAL REACTIONS
COLLISIONS
ELEMENTS
METALS
MOLECULAR BEAMS
MOLECULE COLLISIONS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PLATINUM
PLATINUM METALS
SURFACES
TRANSITION ELEMENTS