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

Voltammetric measurements performed at low [electrolyte]/[reactant] ratios are affected by migrational transport, as well as by ohmic drop contributio ns. The latter depend on the current as well as on the charge of the initia l electroactive species because the local electrolysis changes the ionic co mposition in the vicinity of the electrode. Extraction of thermodynamic or kinetic data from wave shapes and positions is thus impossible without corr ection of these ohmic drop components. This work extends a previous experim ental approach for eliminating ohmic drop contributions from experimental v oltammograms obtained at low [electrolyte]/[reactant] ratios, by combining impedance measurements and voltammetric data. The results presented here co nfirm our previous independent conclusions that when the reactant is neutra l, the variation of ohmic drop along the voltammetric curve (which reflects the progressive ionic enrichment of the diffusion layer) cannot be predict ed by considering diffusional/migrational transport alone, but also require s consideration of the influence of natural convection. (C) 1999 Elsevier S cience S.A. All rights reserved.