Applications of Clay Films as an Electrode Modifier

Abstract

This article reviews the recent works on the application of clay thin films as an electrode modifier. This describes the fundamental mechanisms of a clay-modified electrode as well as the attempts to elucidate various kinds of functional electrodes. A clay-modified electrode is prepared by covering an electrode (e.g. glassy carbon, SnO₂ glass and platinum) with a thin film of clay (<1μm in thickness). When a metal complex is included in the film, the electrode shows reversible redox currents in cyclic voltammetry due to the metal complex. The electrochemical studies also revealed that metal complex in a particular binding state like an ion-paired species diffusing in a clay film to an electrode surface wherein the complex exchanges an electron. Based on the methods, various kinds of functional electrodes have been constructed to achieve asymmetric electrochemical syntheses, ion-selective electrodes and photo-sensitive diodes. New attempts are described to construct a clay film controlled on a molecular scale and to study the mass transfer through the film with the quartz crystal balance methods.