AVS 46th International Symposium
    Applied Surface Science Division Tuesday Sessions
       Session AS-TuA

Paper AS-TuA10
Dynamic Monte Carlo Simulations of Catalytic Surface Reactions: CO + NO on Rhodium

Tuesday, October 26, 1999, 5:00 pm, Room 6A

Session: Modeling in Applied Surface Science
Presenter: J.W. Niemantsverdriet, Eindhoven University of Technology, The Netherlands
Authors: J.W. Niemantsverdriet, Eindhoven University of Technology, The Netherlands
M.J.P. Hopstaken, Eindhoven University of Technology, The Netherlands
J.J. Lukkien, Eindhoven University of Technology, The Netherlands
A.P.J. Jansen, Eindhoven University of Technology, The Netherlands
P.A.J. Hilbers, Eindhoven University of Technology, The Netherlands
Correspondent: Click to Email
A Dynamic Monte Carlo simulation procedure which succesfully describes diffusion, adsorbate interactions, island formation and reconstructions, has recently been described.@footnote 1@ We have used this approach to describe adsorption, desorption and dissociation of NO, as well as reactions between CO and NO on Rh(111) and Rh(100). When NO is adsorbed on Rh(111), TPD shows that the saturation increases from 0.68 ML at 150 K to a 0.75 ML at 225 K.@footnote 2@ This is accompagnied by ordering of the adsorbate layer, as evidenced by LEED. These phenomena are accounted for by a delicate interplay between mobility of and lateral interactions between NO molecules. We have also used Monte Carlo techniques to simulate recent experimental results on NO adsorption at elevated temperatures, where NO adsorbs both dissociatively and molecularly. Static SIMS shows that dissociation starts at 250 K and continuously increases up to 350 K. These experimental observations are satisfactorily explained in the model by adding pairwise repulsive interactions between neighbouring adsorbed species, which increases the activation barrier for dissociation. Similar effects play a role in the explosive reaction between CO and NO on fully occupied surfaces. In addition to repulsive interactions, fast diffusion of adsorbed molecules appears to be essential to reproduce explosive behavior in the simulations. The key point is that for a realistic description of repulsion between adsorbates, one has to consider the local environment of an adsorbed atom or molecule. @FootnoteText@ @footnote 1@ R.J. Gelten, A.P.J. Jansen, R.A. van Santen, J.J. Lukkien, J.P.L. Segers, P.A.J. Hilbers, J. Chem. Phys. 108 (1998) 5921. @footnote 2@ R.M. van Hardeveld, M.J.P. Hopstaken, J.J. Lukkien, P.A.J. Hilbers, A.P.J. Jansen, R.A. van Santen, J.W. Niemantsverdriet, Chem. Phys. Lett. 302 (1999) 98.