Periodic Forcing of NO Reduction on a Pt(100) Surface

Abstract

The influence of a cycled gas feed on reactions of the automotive catalytic converter has been investigated under low pressure conditions ( p < 10 −3 mbar) with a Pt(100) surface as catalyst. Catalytic NO reduction with CO or H 2 as reducing agent was studied in binary mixtures. The reactions were forced around the unstable high rate branch of the rate vs. T hysteresis by applying a square-wave modulation of p CO ( p H2 ). For the NO + CO reaction the yield vs frequency dependence exhibits a pronounced maximum. The pressure modulation causes a periodic structural transformation 1 × 1 ↔ hex. The frequency dependence of the yield is largely related to the average concentration of defects which are created during the phase transition.

Front Waves in the NO + NH3 Reaction on Pt{100}

“…The model also considers the influence of dynamic defects on the kinetic behavior of the reaction, that is, defects created during the 1 × 1 → hex phase transition. The important role of such defects has been shown by Imbihl and co-workers in periodic forcing experiments in the CO + NO reaction on Pt{100} . From these studies, the activation energy for the annealing process could be determined …”