Electrochemical behavior of o-chloranil in aqueous solution at an activated glassy carbon electrode

A study has been conducted on the effect of specific adsorption of o-chloranil, OCA, at an activated glassy carbon electrode, AGCE, surface on its electrochemical behavior in an aqueous solution. The voltammetric responses of OCA at an AGCE show an anodic prepeak and a cathodic postpeak other than the diffusion main couple in weak acidic and neutral pHs. The anodic prepeak and the cathodic postpeak are ascribed to specific adsorption of OCA. The pKa value of the adsorbed redox couple of OCA at an AGCE is at least by 4 and 2 pKa units higher than those of the free redox couple in solution at bare and activated glassy carbon electrodes, respectively. The slop of (Ip)ads/(Ip)diff ratio versus ν1/2 for the cathodic and anodic peaks indicates a stronger adsorption of OCA at AGCE in comparison with OCAH2. The effects of OCA concentration on its adsorption behavior and applied potential on anodic adsorption of OCA at AGCE have been studied and the surface coverage of OCA (ΓOCA) has been calculated.