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.

The effect of temperature on the coupled slow and fast dynamics of an electrochemical oscillator

“…The intricate nonlinear interaction of reactions with disparate time-scales resulting in complex behavior at the solid/liquid electrified interface has been found to be also useful in shedding light on the mechanisms underlying these surface reactions. In this direction, we have recently tackled some intriguing aspects of the complex dynamics of oscillatory electro-oxidation of small organic molecules on platinum and platinum based surfaces 5 6 7 8 9 10 .…”

Dependência da temperatura e do pH da solução e de outros parâmetros na eletro-oxidação de moléculas orgânicas pequenas

“…Due to the more pronounced ensemble effect with an increasing Au presence, no oscillations were found anymore on PtAu 3 and PtAu 9 . As it has been reported previously, the mean potential in the oscillation pattern is dislocated positively slowly along the time series[50,52], what has been assigned a place-exchange process of adsorbed oxygenated species to the subsurface, as described by Conway[28]. Oxide formation is negligible on Au in the visited potential range, that mainly Pt surface atoms undergo this process and become deactivated.…”

Phase diagrams and dynamical evolution of the triple-pathway electro-oxidation of formic acid on platinum

“…The stability diagrams were computed for both galvanostatic and potentiostatic regimes. Previous studies in electrochemical systems were carried out with minimal and generic models, 37,38 in contrast, herein we use a realistic electrochemical model solidly built in experimental evidences. 6…”