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Free keywords:
Thiosulfate;
Gold;
Electro-oxidation;
Bifurcation;
Mixed mode oscillations
Abstract:
We report experimental results on the oscillatory electro-oxidation of thiosulfate on polycrystalline gold electrode in buffered media of pH 6.0. Importantly, we observed oscillations in the current density (potential) when the system was studied under linear sweep of potential (current density). The system displayed supercritical Hopf, period-doubling, homoclinic and bursting bifurcations at different applied currents and potentials. After presenting the dynamics under both potentiostatic and galvanostatic regimes, we characterized the system in terms of its electrical (ohmic drop compensation and electrochemical impedance spectroscopy) and chemical (Capillary Electrophoresis analysis) aspects. Ohmic resistance compensation and electrochemical impedance spectroscopy confirmed the hidden N-shaped negative differential resistance oscillatory character. Capillary electrophoresis analysis revealed the predominance of different oxidation products as a function of the applied potential. Finally, we suggest a tentative mechanism underlying the kinetic instabilities.
