MOLECULAR ASPECTS OF ELECTRON-TRANSFER AT ELECTRODES IN MICELLAR SOLUTIONS

This paper reviews recent advances in understanding electron transfer between electrodes and reactants in micellar solutions, and suggests m olecular pictures for such events. Experimental findings clearly indic ate the influence of surfactant aggregates at the electrode-fluid inte rface in micellar solutions. These aggregates may be arranged in bilay ers, cylinders, or surface micelles depending on the nature of the ele ctrode surface and the surfactant. Entry of an electrochemical reactan t into this dynamic surface film is a key step preceding electron tran sfer. Micelle-bound reactant may dissociate, followed by entry of the reactant into the surface film. Alternatively, the micelle may deliver reactant by joining with surface aggregates. In both cases, the resul t is a mixed adsorbate layer of reactant and non-electroactive surfact ant on the electrode prior to electron transfer. Depending on the reac tant's ability to compete with non-electroactive surfactant for surfac e sites on the electrode, electron transfer can involve adsorbed react ant or reactant which approaches the electrode to within a distance ro ughly equivalent to the diameter of the surfactant head group.