Regensburg 2000 – scientific programme

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O: Oberflächenphysik

O 11: Postersession (Eröffnung)

O 11.104: Poster

Monday, March 27, 2000, 19:00–22:00, Bereich C

Elementary kinetics of the CO + NO Reaction on Rhodium Surfaces — •Marco Hopstaken and Johannes W. Niemantsverdriet — Eindhoven University of Technology, P.O. Box 513, NL-5600 MB Eindhoven

Dissociation of NO is an essential step in the catalytic reduction of NO on rhodium. Here we use TPD/SIMS to study reactions of NO with CO on Rh(100) and compare with similar results on Rh(111) [1]. On both surfaces the reaction rates highly depend on coverage. At low coverage dissociation is completed around 300 K. At saturation, dissociation only starts when NO desorbs i.e. when empty sites become available. At low coverages we find an activation energy of 37 kJ/mole for dissociation of NO on Rh(100), which is 28 kJ/mole lower than on Rh(111). However, formation of nitrogen is slower on the more open Rh(100). This can be explained on the basis of surface chemical reactivity theories. Unexpectedly, the oxidation of CO to carbondioxide proceeds much faster on Rh(100) than on Rh(111). This has important consequences for the kinetics of the CO + NO reaction on the different rhodium surfaces.

1. H.J. Borg, J.P.C.-J.M. Reijerse, R.A. van Santen and J.W. Niemantsverdriet, J. Phys. Chem. 101 (1994) 10052.