Chaotic and periodic switching in cyclic voltammetric responses of methanol and primary alcohols in alkaline solutions

Abstract

The effects of varying the upper potential limit ( upl) on voltammetric responses were studied in applications of cyclic voltammetry to alkaline solutions containing an alcohol. Methanol, ethanol, 1-propanol, 1-butanol and 1-pentanol were the alcohols used. At sufficiently low values of the upl, all solutions exhibited a response in which, after the decay of transient behavior, the current-potential curve would begin to repeat at the beginning of each potential cycle. For solutions containing methanol, ethanol or 1-propanol, increases in the value of the upl caused a drastic change in the response. Cyclic voltammetric behavior was observed in which the current—potential curve repeated after every two cycles in the potential, but not after every cycle. Sustained periodic responses, with periods up to seven times the period of the potential, and aperiodic voltammetric behavior were also realized. Many of the high-order, periodic, cyclic voltammograms appear as combinations of two fundamental voltammograms and the responses can be crudely described as switching between two types of behavior. Experiments were conducted for the purpose of providing an approximate area (measure) in the space ([NaOH] vs. upl) in which high-order, periodic cyclic voltammograms and aperiodic behavior are realized. Over the conditions examined, the measure for methanol was found to be greater than that for ethanol and the measure for these solutes was substantially greater than that found for 1-propanol. In experiments on 1-butanol and 1-pentanol, no evidence was obtained for the existence of high-order, periodic, cyclic voltammograms or aperiodic behavior.