Electrochemical and Electrochemically Modulated Reflectance AC Voltammetry Studies of Electron Transfer Kinetics Between Attached Redox Centers and a Mirror Gold Electrode

Publisher Website
Google Scholar
Abstract
Small amplitude electrochemical ac voltammetry (ACV) is employed to investigate kinetics of electron transfer between Ru redox centers attached to the electrode surface via alkanethiols and gold mirror electrodes. The equations for faradaic admittance of strongly adsorbed electroactive species in the case of a Langmuir isotherm are applied to determine the total coverage of redox centers and kinetic parameters: the standard rate constant and transfer coefficient. appears to increase and appears to decrease as the perturbation frequency increases. In a separate experiment, large amplitude ACV is performed simultaneously with electrochemically modulated reflectance ac voltammetry (EMR ACV) on the same electroactive monolayer/electrode system. The electromodulation reflectance coefficient (X) is defined in the frequency domain as a ratio of ac electroreflectance to both dc electroreflectance and the interfacial ac potential . X is shown to be a more useful quantity than the ratio of ac electroreflectance to dc electroreflectance for representation of the electroreflectance data. X is found to be exactly out‐of‐phase with the faradaic admittance at the wavelength region (410–440 nm) corresponding to the absorption band of the reduced form of the Ru complex. Therefore, the ac electroreflectance signal is dominated by the modulation of the electrode coverage of a given redox state with . Electrochromic effects are negligible. Accurate calculation of from EMR ACV data is complicated because of the nonlinear relationship between the faradaic ac current and large amplitude . Thus, under our experimental conditions, ACV is the preferred method to determine . © 2000 The Electrochemical Society. All rights reserved.

This publication has 0 references indexed in Scilit: