Mixed-mode oscillations in an electrochemical system. II. A periodic–chaotic sequence

We describe a sequence of alternating periodic and chaotic behaviors that occur in the anodic dissolution of copper from a rotating disk in phosphoric acid. Each dynamical state of the sequence possesses a different combination of large and small amplitude oscillations (mixed-mode oscillations). The sequence is generated by incrementing either the potential or rotation speed of the copper-disk electrode. We find that chaotic regimes are linked to periodic regimes through tangent and period-doubling bifurcations. Measured waveforms of the chaotic mixed-mode oscillations can appear as mixtures of the waveforms of the adjacent periodic states. Phase portraits and one-dimensional maps are used to characterize a transition to chaotic mixed-mode oscillations from small amplitude chaotic oscillations. A brief comparison is made with the sequences of mixed-mode oscillations found in the Belousov–Zhabotinski reaction.