Molecular beam studies of the kinetics of the thermal conversion of N2O on Rh(111) single-crystal surfaces

摘要

The thermal conversion of N2O on Rh(111) single-crystal surfaces has been studied using a collimated effusive molecular beam technique coupled with mass spectroscopy detection. The decomposition of pure N2O was determined to occur at temperatures as low as 120 K, to follow first-order kinetics, and to lead to the stoichiometric production of N-2(g) and atomic adsorbed oxygen. Lower rates and total yields are observed with increasing reaction temperatures, presumably because of the increased importance of N2O desorption and surface mobility in the overall kinetics. N2O conversion is poisoned by the adsorbed oxygen byproduct unless a reducing agent such as CO is used for their removal from the surface, in which case N2O reduction can be carried out catalytically. Steady-state reaction rates were determined for different temperatures and N2O:CO beam mixtures, and were deemed controlled by the rate of oxygen removal, not by the decomposition of the N2O. The role of adsorbed N2O as an intermediate during NO reduction is discussed.