Fluctuation-induced transitions and oscillations in catalytic CO oxidation: Monte Carlo simulations

The CO + O2 reaction over Pt-group metals including the Langmuir–Hinshelwood mechanism of CO oxidation and metal oxide formation and removal is considered. Monte Carlo (MC) simulations for a small scale lattice-gas (LG) reaction model and mean-field (MF) equations are suggested to explain the oscillatory CO oxidation. Various scenarios for reaction rate oscillations simulated using the MC method and considerable differences of reaction dynamics produced by the stochastic and deterministic approaches are investigated. Namely, three essentially different types of oscillatory-like behaviour of the small scale LG system are found to occur instead of one type of oscillations in the MF model. Oscillations of the first type are the kinetic ones. They take place both in LG and MF models in the oscillation region of the latter. The dynamical oscillatory-like behaviour of the second and third types is conditioned by intrinsic fluctuations in the small scale LG model. Fluctuation-induced transitions are observed in the region of bistability of the MF model; fluctuation-driven oscillations can appear in monostable region due to exitability of the reaction system.