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1 Wiadomości Chemiczne

1 2024

1 Orlik M.

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Stabilność i niestabilność układów (elektro)chemicznych

100%

Orlik M.

Wiadomości Chemiczne

2024

tom [Z] 78, 7-8

791--829

The article is an introduction to the dynamic self-organization of chemical systems, with particular emphasis on the electrode processes. Experimental manifestations of this type of phenomena include multistability (mainly bistability), spontaneous oscillations of the system’s state, and formation of spatiotemporal patterns. In general, such phenomena occur when a single steady state loses stability in favor of other, more complex dynamic behaviors, which are possible in systems with non-linear characteristics containing steps of positive and negative feedback loops in their kinetic mechanisms. From a mathematical point of view, the transition to multistability or oscillations means appropriate bifurcations in the solutions of differential equations describing the dynamics of the system. With regard to electrochemical systems, the key role of negative differential resistance (N or S type) in the current-potential characteristics of the electrode processes has been indicated as the typical cause of feedback loop. In the presence of appropriate series resistance in the electrical circuit, combined with the relatively slow diffusion of reactants into the electrode, this can lead to oscillations, as well as to multistability. A linear stability analysis of a one- and two-dimensional electrochemical system is outlined, with the diagnosis of the saddle-node bifurcation (the route to multistability) and the Hopf bifurcation (the typical route to oscillation). For illustrative purposes, selected manifestations of dynamic self-organization are summarized: oscillations and bistability in the electroreduction of nickel(II) thiocyanate complexes, tristability in the electroreduction of azide nickel(II) complexes, convectively generated bistability in the electroreduction of Hg(II) and the formation of luminescent convective structures in thin-film electrolysis of rubrene.