The mechanism of kinetic oscillations in the NO + CO reaction on Pt(100)

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 COad and NOad