Steady state voltammetry at low electrolyte/reactant concentration ratios: what is means and what it does not mean

摘要

Voltammetric measurements performed at low [electrolyte]/[reactant] ratios are affected by migrational transport. as well as by ohmic drop contributions. The latter depend on the current as well as on the charge of the initial electroactive species because the local electrolysis changes the ionic composition in the vicinity of the electrode. Extraction of thermodynamic or kinetic data from wave shapes and positions is thus impossible without correction of these ohmic drop components. This work extends a previous experimental approach form eliminating ohmic drop contributions for experimental voltammograms obtained at low [electrolyte]/[reactant] ratios, by combining impedance measurements and voltammetric data. The results presented here confirm our previous independent conclusions that when the reactant is neutral, the variation of ohmic drop along the voltammetric curve (which reflects the progressive ionic enrichment of the diffusion layer) cannot be predicted by considering diffusional/migrational transport alone, but also requires consideration of the influence of natural convection.