Evidence for an N₂O intermediate in the catalytic reduction of NO to N₂ on rhodium surfaces

Abstract

Rates for isotopically labelled molecular nitrogen production during the isothermal steady-state reduction of NO to N₂ by CO on Rh(1 1 1) surfaces were measured by using a molecular beam technique. The replacement of surface ¹⁴N by ¹⁵N upon switching the isotopic nitrogen label in the NO (from ¹⁴NO to ¹⁵NO) was determined to occur via the exclusive formation of ¹⁴N¹⁵N; no ¹⁴N¹⁴N was detected in these experiments. This result provides direct kinetic evidence for a mechanism for molecular nitrogen production involving the formation of an N-NO intermediate. The implications for the design of catalytic converters are briefly discussed.