Self-organized reactivity patterns during the oxidation of H₂-CO mixtures on a rotating Pt ring-electrode

We report the spontaneous formation of spatial reactivity patterns during the oxidation of H₂/CO mixtures in diluted perchloric acid on a rotating Pt ring-electrode. Under potentiostatic conditions, the system is oscillatory. At the onset of oscillations at low applied voltage, regular spatio-temporal structures form. At intermediate and high applied voltages spatio-temporal chaos is observed, which exhibits an increasing number of high reactivity spikes with increasing voltage. The transition between the regular and chaotic regime is rather complex and involves period-doubled states. Under galvanostatic conditions, a similar spatio-temporal scenario is observed as a function of applied current.