NONLINEAR EFFECTS IN ADSORPTION AND REACTION DYNAMICS AT SURFACES: KINETIC OSCILLATIONS UNDER SCRUTINY

Abstract

A number of catalytic reactions exhibit complex dynamical behavior, including kinetic oscillations with both temporal and spatial characteristics. Attention has been focused on the CO+ NO and CO+O2 reactions on Pt{100}. Recent molecular beam studies conducted at Cambridge on the interaction of CO with Pt{100} have provided the basis for a new mechanism for oscillatory behavior. The rate of growth of (1×1) islands on the quasihexagonal reconstructed phase of Pt{100} is strongly nonlinear with respect to the local CO coverage on the hex-R phase at temperatures between 380 and 410 K, with a reaction order of 4. This strong nonlinearity results in a flux-dependent sticking probability for CO at this temperature, and detailed modeling also reproduces the major features in the oscillatory behavior observed for the CO+NO reaction. An important effect of the nonlinearity in both the CO+NO and CO+O2 oscillatory behavior at high temperatures is the maintenance of in-phase behavior across the surface during oscillations.