Carbon monoxide oxidation on the Pt(111) surface: Temperature programmed reaction of coadsorbed atomic oxygen and carbon monoxide
- 15 January 1983
- journal article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 78 (2), 963-974
- https://doi.org/10.1063/1.444801
Abstract
Carbon dioxide formation from coadsorbed atomic oxygen and molecular carbon monoxide has been characterized using temperature programmed reaction spectroscopy over a wide range of initial oxygen and carbon monoxide coverages. The experiments were performed in an apparatus containing Auger electron spectroscopy, low energy electron diffraction, and a multiplexed mass spectrometer for the temperature programmed reaction experiments. A single reaction limited CO2 peak is observed in the 320–340 K temperature range over a wide range of initial atomic oxygen and molecular CO coverages, suggesting that a single reaction mechanism dominates. The activation energy for CO2 formation ranges from 166 kJ/mol (40 kcal/mol) for small surface concentrations of reactive adsorbed atomic oxygen and CO (0.4×1014/cm2) to 68 kJ/mol (17 kcal/mol) for larger surface concentrations of reactive adsorbed atomic oxygen and CO (2.5×1014/cm2). Low energy electron diffraction results indicate that adsorbed atomic oxygen forms islands for surface concentrations greater than about 0.4×1014 atoms/cm2 (0.10 θmax) and suggests that CO forms CO islands when CO is adsorbed on surfaces containing adsorbed atomic oxygen. The observation that this reaction does not go to completion during a temperature programmed reaction cycle indicates that the island structure of the reactants limits their availability for reaction. Apparently, the reaction proceeds by diffusion of adsorbed CO to the perimeters of the immobile adsorbed atomic oxygen islands. Similar effects have been observed previously during temperature programmed reaction and titration studies of the hydrogen–oxygen reaction on the Pt (111) surface {J. L. Gland, G. B. Fisher, and E. B. Kollin [J. Catal. 77, 263(1982)]}.Keywords
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