Fast surface reaction study using ultramicroelectrodes

Abstract

Cyclic voltammetry is a powerful tool for the study of surface reaction kinetics. On the other hand, the upper limit of measurability of the rate constant is often restricted by the shortest experimental time scale which can be achieved. When ultramicroelectrodes are used, the scan rate of cyclic voltammetry can be increased by several orders of magnitude; the examination of kinetic parameters for very fast surface reactions is thus possible. The electron transfer process of several adsorptive species at mercury ultramicroelectrodes has been investigated. The surface reaction rate constant above 500,000 s −1 can be measured readily while the scan rate is at 100 kV s −1 or higher. The ratio of the faradaic current to the charging current is usually high. However, both charging current and faradaic current contribute a sizable iR drop and the data could be distorted, especially at very high scan rates. To evaluate the kinetic parameters reliably, the solution resistance has to be determined and corrected. The approaches for ohmic drop correction are discussed.