Development of Microelectrode techniques for analytical and environmental applications

Abstract

As a result of several unique advantages of microelectrodes, there has been a great deal of interest in their development for electrochemical measurements. The aim of this study was to develop microelectrode techniques for analytical and environment applications.

It is well established that dilute aqueous solutions of acids show a wave for H⁺ ion reduction, this feature has since been employed analytically. By analogy, an oxidation wave would be expected from dilute solutions to bases. The voltammetric behaviour for the electrochemical oxidation of aqueous solutions containing strong bases was studied with microdisc electrodes and rotating disc electrode (RDE). A well-defined wave for OH^- oxidation was obtained at the foot of the current increase due to O₂ evolution. The limiting current of this wave was tested against OH^- concentrations, the microdisc radius and RDE rotation speed. The characteristic features of the OH^- oxidation wave, which include the wave split, the position and shape of the wave, were also examined as a function of the microdisc radius, RDE rotation speed and OH^- concentrations. The results reported in this study provide the first experimental evidence for the diffusion-controlled electrochemical oxidation of OH^- ions in aqueous solutions. The exact mechanism of the oxidation process occurs through a complex pathway which involves multiple electron transfer steps; the scanning electrochemical microscopy technique was used to investigate OH^- ions oxidation by probing the release and consumption of the species that accompany the oxidation process.

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