AN ELECTROCHEMICAL MECHANISM FOR THE VOLTAMMETRIC OXIDATION OF METHANOL AND ITS RELATIONSHIP WITH PERIOD-DOUBLING BIFURCATIONS

The changes in behavior that lead to a period-doubling bifurcation wer e investigated in the application of cyclic voltammetry to the oxidati on of methanol at a rotating platinum disk electrode in alkaline solut ion. Two parameters were separately varied, the concentration of metha nol and the upper potential limit of the potential cycle. Feedback mec hanisms that explain the changes in behavior are formulated from exper imental data and an electrochemical mechanism. Evidence is presented t hat indicates a period-two cyclic voltammogram occurs due to the dual role played by the surface species PtOH. During one cycle of the perio d-two response, most of the PtOH that forms on the surface reacts with an intermediate of methanol oxidation. During the other cycle a subst antial amount of PtOH is transformed to Pt oxides. A Mobius strip that formed before the period-doubling bifurcation was detected by examini ng current-potential curves. Near the point in parameter space where t he Mobius strip formed the relaxation was fastest.