Electroanalytical Chemistry Based on the Theories of an Electrical Double Layer and a Reaction-diffusion Layer

Abstract

Electrochemically active (charged and/or redox active) species are under the influence of the electric field at the electrode surface. Electrochemical reactions vary the concentration of the electrochemically active species at the electrode surface from the bulk solution. The reaction fields affected by the electric potential and the chemical potential gradients are known as the electrochemical double layer and the diffusion layer, respectively. Three characteristic situations, such as the electrical double layer at a microporous electrode, potential-dependent adsorption of redox active ion, and bioelectrocatalytic reaction at a micro electrode, are modeled and numerically simulated. In a micro pore, the electrical double layers will overlap with each other. This overlapping causes a decrement of the double layer capacitance of the electrode. The adsorption of the charged redox active species at the electrode surface depends on the electrode potential. The maximum adsorption occurs around its standard redox potential. The mediator-type bioelectrocatalytic reaction at the microelectrode is able to provides a steady-state current. When the enzymatic reaction is extremely fast, the current is controlled by the diffusion of the substrate. Understanding the concentration profiles of the components in the system will provide an understanding of electrochemical reactions.