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

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.