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Abstract

Under constant flow conditions the reaction of NO and CO to the products N₂ and CO₂ on a Pt(100) surface exhibits multiple steady states and kinetic oscillations. Using Video LEED, measurement of the work function change and of the reaction rate the kinetic oscillations were investigateed in the 10⁻⁷ mbar range. Kinetic oscillations were found to occur in two separate temperature regions around 400 K. In the upper temperature range, the oscillations are coupled to the 1 × 1 ⇌ hex phase transition, while those in the lower temperature range proceed entirely on a 1 × 1 surface. Based on a mathematical model consisting of three coupled differential equations it could be shown that the 1 × 1 ⇌ hex phase transition is not essential for the oscillating mechanism. The main role in the mechanism can instead be ascribed to the autocatalytic behavior of the surface reaction between CO_ad and NO_ad.