We studied the mechanism of the N + NO reaction on Rh(111) surfaces by means of near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Atomic nitrogen layers on Rh(111) were titrated with NO at various temperatures. Below 350 K, the chemisorbed NO monomer does not react with N, while the NO dimer formed in the second layer acts as an extrinsic precursor to the reaction: N(a) + (NO)2(a)→N2O(g) + NO(a). Because of a dominant role of the precursor-mediated mechanism, the reaction proceeds slower with an increase in temperature. Above 350 K, the reaction switches to a different path: N(a) + NO(a) → N2(g) + O(a). ?.
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