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Volume 120, 2002
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Spatial bifurcations of fixed points and limit cycles during the electrochemical oxidation of H2 on Pt ring-electrodes

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Abstract

Pattern formation during the oscillatory oxidation of H2 on Pt ring-electrodes in the presence of electrosorbing ions was studied under potentiostatic control for three different positions of the reference electrode (RE). The position of the RE crucially affects the degree of the global feedback which is imposed by the potentiostatic operation mode, and the three configurations selected corresponded to zero, maximum and intermediate global coupling. In the absence of global coupling, ‘ communication’ among different positions occurs exclusively through migration coupling (the electrochemical counterpart to diffusion in reaction–diffusion systems). In this case, spatially inhomogeneous oscillations that were attributed to a spatial bifurcation of the homogeneous limit cycle were observed throughout. This implies that the system is Benjamin–Feir unstable. For the strongest global coupling adjustable, travelling pulses were found that emerged in a wave bifurcation with n = 1 from the homogeneous steady state. The pulses exhibited modulations in velocity and width that most likely resulted from the interaction between inhomogeneities of the catalytic surface and the nonlinear reaction dynamics. In the case of an intermediate global coupling strength, a diversity of spatio-temporal motions was observed. The dynamics ranged from pulses over target patterns and so-called asymmetric target patterns to mixed states where two or three of these states alternate. For some parameters these mixed states were in addition separated by bursts of the system to a nearly homogeneous unreactive state.

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Publication details

The article was received on 12 Apr 2001 and first published on 12 Nov 2001


Article type: Paper
DOI: 10.1039/B103345J
Citation: Faraday Discuss., 2002,120, 165-178
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    Spatial bifurcations of fixed points and limit cycles during the electrochemical oxidation of H2 on Pt ring-electrodes

    P. Grauel, H. Varela and K. Krischer, Faraday Discuss., 2002, 120, 165
    DOI: 10.1039/B103345J

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