Influence of Organic Solvents on the Kinetics of Electron Transfer and the Adsorption at Highly Oriented Pyrolytic Graphite

Acetonitrile and several other common organic solvents have been found to dramatically influence the kinetics of electron transfer and the adsorption at freshly cleaved highly oriented pyrolytic graphite (HOPG). Ferricyanide and anthraquinone-2,6-disulfonate were used to investigate the effect of several pretreatment procedures including cleaving, electrochemical pretreatment, and thermal etching on the activity of basal plane HOPG. The results of this work suggest that although active sites produced by cleaving are relatively stable in air and in aqueous solution, exposure to organic solvents quickly and irreversibly passivates them toward simple outer-sphere electron transfer and adsorption. In contrast, electrochemically pretreated and thermally etched HOPG is much less sensitive to organic solvents, suggesting that the natures of the active sites produced by these methods are significantly different. As a result, it is important to take into account this behavior when using freshly cleaved HOPG in surface and electrochemical studies.