Simulated low-support voltammetry: Deviations from Ohm's Law

Publication date: Available online 18 October 2018Source: Journal of Electroanalytical ChemistryAuthor(s): Christopher Batchelor-McAuley, Kamonwad Ngamchuea, Richard G. ComptonAbstractTo what extent can the resistance of a voltammetric system be considered a constant and well described by Ohm's law? Many real electrochemical systems are neither fully in the macro or microscopic limit. Through simulation this work looks at the transition between the steady-state and transient (macroelectrode) mass-transport limits for electrochemical systems, focusing on the influence of ohmic drop on the voltammetric response. Approximate analytical expressions are provided to yield an estimate of the minimum electrolyte to analyte support ratio required to obtain a diffusion only voltammetric response in the absence of convection. Subsequently, this work evidences how for systems in which the electrolyte to analyte ratio is less than unity and the dimensionless scan rate is less than ~400, then the cell resistance cannot be considered constant. Furthermore, it is demonstrated how under low support conditions the time required to reach voltammetric steady-state is greater than is found for diffusion only systems- this arises due to significant changes in the electrolyte concentrations in the vicinity of the electrode during the course of the voltammetric scan.

Source: Journal of Electroanalytical Chemistry - October 19, 2018 Category: Chemistry Source Type: research