Non-unity stoichiometric reversible electrode reactions. The effect of coupled kinetics and the oxidation of bromide

We explore via simulation, the cyclic voltammetry of the following mechanism involving a reversible electrode process coupled with a follow up reaction in which the product (B) of the electrode reaction reacts chemically with the reactant, A, to form a species C: 2A−2e−⇄B B þ A⇌k f kb C Such a mechanism is shown, under certain critical combinations of rate constant and reactant concentration to give rise to two voltammetric peaks despite the assumption of a single redox couple (A/B). This results from the formation of C during the first peak whilst the second peak, seen at more oxidizing potentials, reflects the dissociation of C releasing A. A mechanism of the type investigated may hold during the oxidation of bromide(Br−, A) in solution to form bromine(Br2, B) and tribromide (Br3−,C). Simulations are used to explore the conditions for which two peaks are expected in the bromide oxidation system in aqueous solution and for which the two following limiting cases operate 3Br−−2e−⇄Br− and 2Br−−2e−⇄Br2 We report experimental data for the bromide oxidation in aqueous solution. These are interpreted via simulations using independent literature values for the rate and equilibrium constants for tribromide formation