Differential pulse techniques in weakly supported media: Changes in the kinetics and thermodynamics of electrode processes resulting from the supporting electrolyte concentration

Square wave voltammetry (SWV) and differential multipulse voltammetry (DMPV) in weakly supported media are investigated. The numerical simulation procedures reported in literature (Streeter et al., J. Phys. Chem. C 112 (2008) 13716–13728; Limon-Petersen et al., J. Phys. Chem. C 114 (2010) 2227–2236) for electrochemical experiments in low conductivity solutions is applied with success. From this theory, the influence of the concentration of supporting electrolyte on the voltammograms is discussed for different redox couples and at electrodes of different size. The variation of the peak current and peak potential due to migration and ohmic drop effects are reported. The theory is applied to the experimental study of the one-electron reduction processes of cobaltocenium and cobalt (III) sepulchrate at mercury hemispherical electrodes of 25 μm radius. The kinetic parameters and formal potential are obtained in a wide range of support ratio from the SWV and DMPV voltammograms. Possible changes of the kinetic and thermodynamic properties of the electrode reactions are analyzed as a function of the level of support.

► Square wave and differential multipulse voltammetries at low support are studied.
► Distortions of the voltammograms due to migration and ohmic drop effects are analyzed.
► Experimental study of effects of supporting electrolyte concentration is carried out.
► A noteworthy shift of the formal potential of cobaltsepulchrate in water is observed.