The NO + NH 3 reaction on Pt(100): steady state and oscillatory kinetics

Abstract

The NO + NH 3 reaction was investigated on a Pt(100) surface in the 10 −6 mbar range using Video-LEED, work function measurements and measurements of the product partial pressures of N 2 and H 2O. Sustained kinetic oscillations, as observed in the N 2, H 2O and work function signals, were detected between 425 and 450 K for p NO = 1.1 × 10 −6 mbar and p NH 3 = 4.7 × 10 −6 mbar. The dependence of the oscillation period on temperature and on the p NH 3 / p NO ratio was determined. In situ LEED measurements demonstrated that oscillations in the reaction rate are coupled to the 1 × 1 ⇄ hex phase transition. Isotopic exchange experiments with 15NO and 14NH 3 showed that depending on the temperature and p NH 3 / p NO ratio, significant deviations from a random mixing of 15N and 14N on the surface occur. This is interpreted as indication for an attractive interaction between NO ad and NH xad ( x = 1–3).