Reaction of coadsorbed nitric oxide and nitrogen atoms on Rh(111)

We have studied the reaction of nitrogen atoms (N) with nitric oxide molecules (NO) coadsorbed on a Rh(lll) catalyst in order to isolate the reaction of these two species as an elementary step (e.g., in the NO + CO reaction mechanism) and determine the products of that reaction, Electron beam dissociation of adsorbed NO was used to cleanly prepare N atom coverages between 0.05 and 0.5 monolayers. By using isotopically labeled NO and N reactants, we determined that NO and N react, under our conditions, to form only N2O. In contrast to previous reports, we see no evidence that suggests that NO and N can react to form N-2 as a product. In complementary experiments, we have completed computer modeling of an NO temperature-programmed desorption experiment. These simulations show that NO dissociation rates in the high NO coverage limit are as much as 500 times slower than previously reported dissociation in the low coverage limit. (C) 1995 Academic Press, Inc.