Glassy Carbon Electrode Electromodification in the Presence of Organic Monomers: Electropolymerization versus Activation

Several reports in the literature deal with the modification of glassy carbon electrode (GCE) surface via electropolymerization of some organic monomers, particularly p-aminobenzenesulfonic acid (p-ABSA) and L-cysteine using intensive oxidative conditions, and attributed the improved electrocatalytic activities toward various analytes to the formation of the electropolymerized layer. What is the real cause for this improvement in electrocatalytic activity? Is it because of the electrochemical activation process of GCE or electropolymerization? Combining a set of surface and electrochemical characterization techniques, we first showed that the electrochemical peaks previously assigned in many reports to electropolymerization processes at the surface of GCE correspond to electrochemical activation of the GCE surface. We further demonstrated that the anodization of GCE at high voltage causes activation of its surface and the formation of surface functional groups (SFGs). In fact, those SFGs are found to be the main reason for the enhancement in electrocatalytic activity of the activated GCE (AGCE). The surface features of the modified electrodes were characterized by Raman spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The electrochemical behavior was investigated using cyclic voltammetry (CV). The analytical performance of AGCE toward dopamine (DA) was assessed using differential pulse voltammetry (DPV). As compared to the previously reported dopamine electrochemical sensors assuming such electropolymerization processes, the AGCE showed analytical performance practically similar to that of these sensors. This further confirms that the enhancement in electrocatalytic activity is due to the electrochemical activation of the GCE surface.