title: Coupled slow and fast surface dynamics in an electrocatalytic oscillator: model and simulations.
abstract: The co-existence of disparate time scales is pervasive in many systems. In particular for surface reactions, it has been shown that the long-term evolution of the core oscillator is decisively influenced by slow surface changes, such as progressing deactivation. Here we present an in-depth numerical investigation of the coupled slow and fast surface dynamics in an electrocatalytic oscillator. The model consists of four nonlinear coupled ordinary differential equations, investigated over a wide parameter range. Besides the conventional bifurcation analysis, the system was studied by means of high-resolution period and Lyapunov diagrams. It was observed that the bifurcation diagram changes considerably as the irreversible surface poisoning evolves, and the oscillatory region shrinks. The qualitative dynamics changes accordingly and the chaotic oscillations are dramatically suppressed. Nevertheless, periodic cascades are preserved in a confined region of the resistance vs. voltage diagram. Numerical results are compared to experiments published earlier and the latter reinterpreted. Finally, the comprehensive description of the time-evolution in the period and Lyapunov diagrams suggests further experimental studies correlating the evolution of the system's dynamics with changes of the catalyst structure.
authors.affiliation: Institute of Chemistry of São Carlos, University of São Paulo, PO Box 780, 13560-970, São Carlos, SP, Brazil.
authors.forename: Melke A
authors.initials: MA
authors.lastname: Nascimento
authors.affiliation: Institute of Chemistry of São Carlos, University of São Paulo, PO Box 780, 13560-970, São Carlos, SP, Brazil.
authors.forename: Raphael
authors.initials: R
authors.lastname: Nagao
authors.affiliation: Fritz Haber Institute of the Max Planck Society, Department of Physical Chemistry, Faradayweg 4-6, D-14195 Berlin, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Eiswirth
authors.affiliation: Institute of Chemistry of São Carlos, University of São Paulo, PO Box 780, 13560-970, São Carlos, SP, Brazil.
authors.forename: Hamilton
authors.initials: H
authors.lastname: Varela