Campus Units

Physics and Astronomy, Mathematics, Ames Laboratory

Document Type

Article

Publication Date

5-1998

Journal or Book Title

Journal of Chemical Physics

Volume

108

Issue

18

First Page

7795

Last Page

7806

DOI

10.1063/1.476215

Abstract

A lattice-gas model is developed to describe the reactive removal of a preadsorbed, mixed NO+COadlayer covering a Pt(100) surface, via reduction of NO with CO, and behavior of the model is analyzed. Since NO dissociation requires an adjacent empty site, the NO+CO covered surface constitutes an unstable steady state. The creation of vacancies leads NO dissociation, the reaction of CO with the O formed by dissociation, the subsequent creation of more vacancies, and thus the autocatalytic removal of the adlayer. The high mobility of most adspecies leads to an initial “disperse stage” of adlayer removal, characterized by an exponential increase in the number of highly dispersed vacancies. Thereafter follows a transition to a “reaction front propagation” stage of adlayer removal, where a chemical wave develops that propagates into the NO+CO covered region of the surface with roughly constant velocity, and leaves in its wake a surface populated only by excess reactant. We provide a suitable rate equation formulation for the initial disperse stage, but focus on a reaction-diffusion equation analysis of reaction front propagation, examining, in detail, behavior for long times where the front is nearly planar. We emphasize that it is necessary to incorporate the coverage-dependent and tensorial nature of chemical diffusion in the mixed adlayer. Both these features reflect the interference on the surfacediffusion of each adspecies by coadsorbed species. Thus, a key component of this work is the development of an appropriate treatment of chemical diffusion in mixed layers of several adspecies.

Comments

The following article appeared in Journal of Chemical Physics 108, 18 (1998): 7795 and may be found at doi: 10.1063/1.476215.

Rights

Copyright 1998 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.

Copyright Owner

American Institute of Physics

Language

en

File Format

application/pdf

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