Evidence for an N2O intermediate in the catalytic reduction of NO to N-2 on rhodium surfaces

Rates for isotopically labelled molecular nitrogen production during the is othermal steady-state reduction of NO to N-2 by CO on Rh(1 1 1) surfaces we re measured by using a molecular beam technique. The replacement of surface N-14 by N-15 upon switching the isotopic nitrogen label in the NO (from (N O)-N-14 to (NO)-N-15) was determined to occur via the exclusive formation o f (NN)-N-14-N-15; no (NN)-N-14-N-14 was detected in these experiments. This result provides direct kinetic evidence for a mechanism for molecular nitr ogen production involving the formation of an N-NO intermediate. The implic ations for the design of catalytic converters are briefly discussed. (C) 20 00 Elsevier Science B.V. All rights reserved.