Loss and Recovery of Faradaic Response on Glassy Carbon Electrodes: Effect of Electrochemical Pretreatments on Oxide Layer Properties

Abstract

Due to the complexity of the glassy carbon (GC) | electrolyte interface, several physical, chemical, and electrochemical activation methods have been developed, mainly to obtain both high activities for heterogeneous charge transfer and reproducibility. One of the most simple and widely used methods in the pretreatment of GC electrodes is oxidation in aqueous media with different electrolytes at variable pH. This oxidation can be made through dynamic and/or constant programs of potential. In this work we studied the kinetics of heterogeneous charge transfer for several couples after different pretreatment procedures: potential cycling and application of a constant anodic potential. In the dynamic method, the results are correlated with an activation parameter. Total lack of faradaic current is observed when the electrode surface is oxidized under a constant potential regime, indicating that the electrode acts as a dielectric. The loss and recovery of electrochemical activity of the GC electrode occur in a gradual way as a function of the injected oxidation and reduction charges. This fact is very important in systems where carbon materials are used as electrodes under a continuous oxidation regime, such as high-pressure liquid chromatographic (HPLC) electrochemical detectors, batteries, capacitors, and for the generation of polymers, by potentiostatic oxidation. © 2001 The Electrochemical Society. All rights reserved.