Voltammetry of Adsorbed Molecules. Part 2: Irreversible Redox Systems

Abstract

Information about the kinetics of reactions can readily be extracted from linear sweep voltammograms of adsorbates which show irreversible behavior if the adsorbates behave ideally. Factors which cause nonideal behavior include lateral interactions between adsorbates, influence of solvent reorganization energies, and kinetic dispersion. The difficulties in extracting information on the kinetics of adsorbed redox systems which behave nonideally are discussed. Diagnostic criteria are provided from which it may be determined which of the above phenomena, if any, are effecting the voltammetric response.

Electrochemical interaction of Shewanella oneidensis MR-1 and its outer membrane cytochromes OmcA and MtrC with hematite electrodes

“…This is not surprising because there are many possibilities for kinetic dispersion (i.e., hemes exchanging electrons with the electrode at different energies and rates), blocking layers, and other effects in our system. For perfectly irreversible electron transfer with an adsorbed layer, cathodic peaks should be 62.5/an mV wide (Honeychurch and Rechnitz, 1998), which for n = 1 and a = 0.5 equals 125 mV. This is closer to those that we observe, though our system is probably neither perfectly reversible nor perfectly irreversible.…”

“…As background, the overpotential g is the difference between E 00 and either E pc (giving the cathodic overpotential g c ) or E pa (giving the anodic overpotential g a ). The Laviron equation relates the electron transfer rate constant k to peak position for a layer of redox-active adsorbed molecules (Laviron, 1979;Honeychurch and Rechnitz, 1998):…”

Electrochemical Comparative Study of Riboflavin, FMN and FAD Immobilized on the Silica Gel Modified with Zirconium Oxide

“…This behavior suggests a good electron transfer rate between the adsorbed flavins and the electrode. 33,34 The number of electrons transferred between the electrode and the adsorbed flavin during the redox process were calculated using the equation E fwhm = 90.6/n, where n is the number of electrons participating in the reaction and E fwhm is the peak width at half height. 31,33 For the three adsorbed flavin on Si:Zr, the number of electrons was close to 1.5, which indicates that part of the flavins are going to a semiquinone state during the redox process.…”

Detection of interaction between redox centers of surface confined molecules by means of Cyclic Voltammetry and Differential Staircase Voltcoulommetry

“…The study of charge transfer reactions with adsorbed species in Cyclic Voltammetry (CV) was developed by Laviron [23], who deduced simple methods for the analysis of these systems [23,24]. Nevertheless, CV also presents disadvantages for studying surface redox processes, mainly derived from complex double layer influences associated to the I-E response [25][26][27][28], and low faradaic-to-background ratios observed when monolayers of biomolecules are considered [10,12,15]. These non-idealities of CV are responsible for the low agreement between theory and experiments observed with this technique.…”