OBSERVATION OF BISTABILITY IN CYCLIC VOLTAMMETRIC EXPERIMENTS ON ETHANOL, PROPANOL, BUTANOL AND FORMIC-ACID FORMATE

The effects of varying the lower potential limit were studied in cyclic voltammetric experiments conducted on several electrocatalysed oxidation processes: the oxidation of formic acid/formate, ethanol, propanol and butanol. In an acidic medium, each oxidation process, subjected to a cycling potential, exhibited a bistable response over a range of values in the lower potential limit. Within the region of bistability, two different cyclic voltammograms, one with a relatively large amplitude and one with a small amplitude, were found to coexist. Experiments conducted on the oxidation of butanol revealed that the region of bistability decreases in size with respect to increases in the alkalinity of the solution; a result that is consistent with the description of bistability provided by the theory of catastrophes. The cause of the cyclic voltammetric bistability is explained in terms of a nonlinear feedback mechanism involving a reaction between strongly bound carbon monoxide and oxides. The reaction couples an indirect path of the oxidation processes to the process by which an oxide layer is formed.