Quantification of Electrocatalytic Activity of Glassy Carbon Electrode

•Glassy carbon (GC) surface modified by reproducible electrochemical procedure.•GC surface characterized by XPS, Raman spectroscopy and contact angle measurement.•Standard rate constants of electron transfer (k°) of redox couples determined.•k° determined by scanning electrochemical microscopy and cyclic voltammetry.•Correlation between k° values and surface composition evaluated. Despite the fact that carbon represents one of the most important electrode materials today, an electrocatalysis at its surfaces is far from being understood. In the present work, a detailed investigation of electrocatalytic properties of well characterised glassy carbon (GC) surfaces prepared by defined electrochemical activation procedure was performed. In order to achieve this goal, standard rate constants of various redox couples used as probes were correlated with the information about the electrodes surface composition. In particular, the GC electrode surface was characterised by Raman spectroscopy, water contact angle, 9,10-phenanthrenequinone adsorption and X-ray photoelectron spectroscopy. Standard rate constants of Fe3+/2+, V3+/2+, Eu3+/2+, TEMPO+/• and [Fe(CN)6]3-/4- redox couples were determined by cyclic voltammetry and scanning electrochemical microscopy. Results confirmed the importance of C=O moiety as a catalytic site for Fe3+/2+ and possibly also V3+/2+ and TEMPO+/• couples. Negatively charged oxygen-containing surface species were suggested as novel catalytic sites for Eu3+/2+. An evidence was found that a redox process of 1,4-benzoquinone/hydroquinone is catalysed by the very same surface species. However, the electrocatalysis in this case seems to be influenced also by the adsorption of these compounds at the electrode. Standard rate constant of [Fe(CN)6]3-/4-, often used as a probe for electrochemical testing of electrode surfaces, could not be correlated to any of the considered surface species. [Display omitted]