Theoretical model of ion transfer-electron transfer coupled reactions at the thick-film modified electrodes

•Theory of IT-ET coupled reactions in a thick film modified electrode is developed.•Distribution potential of the L-L interface are incorporated into the model.•Experimental guidelines emerging from the model are provided.

The theory of cyclic voltammetry of ion transfer-electron transfer coupled reactions in a thick organic film modified electrode is developed. The model system consists of a planar electrode completely covered by an organic phase, which in turn is in contact with an aqueous phase, each containing a supporting electrolyte. It is shown that the coupling between the ion transfer-electron transfer processes at both, solid∣liquid and liquid∣liquid interfaces, has a marked effect on the shape of the voltammogram. The model allows the analysis of the system in different experimental conditions. In particular, the results for different concentration ratios of the redox probe and supporting electrolytes are presented. The variation of the potential of the solid∣liquid and the liquid∣liquid interfaces reflects changes in concentration of the species involved. This variation is presented as a descriptor of the shape of the voltammograms. The theoretical results are contrasted with experimental behaviour reported in literature.

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