On the mechanism for the reduction of nitrogen monoxide on Rh(111) single-crystal surfaces

Abstract

Isothermal kinetic experiments were carried out with isotopically-labeled molecular beams in order to characterize the surface reactions involved in the reduction of nitrogen monoxide with carbon monoxide on Rh(111) single-crystal surfaces. The new data reported here offers support for the basic model advanced previously where N₂ production takes place via the formation of N–NO intermediates at the periphery of atomic nitrogen surface islands. However, they also highlight a few additional subtle complications. In particular, the rapid desorption of a small amount of ¹⁴N¹⁴N upon switching from ¹⁴NO + CO to ¹⁵NO + CO mixtures points to the role of additional adsorbates nearby the reaction surface site in facilitating the dissociation of the N–NO intermediates. In addition, the results from experiments with mixed ¹⁴NO + ¹⁵NO + CO indicate a combination of reactions at the edges of previously deposited ¹⁴N islands and the growth of new mixed ¹⁴N + ¹⁵N surface clusters.