Functionalization of glassy carbon electrodes with metal-based species

Substituted phenyl-modified glassy carbon electrodes were functionalized with metal/metal oxide/ metal hydroxide and inorganic compounds. More specifically, the glassy carbon electrodes were first functionalized with 4-sulfonate phenyl and N,N-diethylaniline groups by electrochemical reduction of the corresponding diazonium salt in nonaqueous media. Second, the functionalized electrodes were soaked in a solution containing the metallic ions and treated with a reductant (NaBH(4)) in the case of the formation of the Ru- and Cu-based species or with redox species (Fe(II) or Fe(CN)(6)(3-)) in the case of Prussian Blue. The resulting Cu/Cu(OH)(2) and RuO(2)/Ru(OH)(2)-modified glassy carbon electrodes displayed electrochemical activity for selected reaction such as nitrate reduction and hydrogen peroxide oxidation, respectively. X-ray photoelectron spectroscopy was also used to confirm the presence of the metallic species and Prussian Blue at the electrode surfaces. The curve-fitting of the appropriate core level spectra was useful to distinguish between the oxide/hydroxide species and the metallic state. The atomic concentration of the metal-based species at the surface of the modified glassy carbon electrodes, estimated from the XPS data, ranged between 0.2 and 1 at. %, which corresponds to surface concentration of 0.55 x 10(-10), 0.87 x 10(-10), and 0.21 x 10(-10) mol/cm(2) for Cu, Ru, and Prussian Blue, respectively. These relatively low surface concentrations and the scanning electron micrographs of copper- or ruthenium-modified glassy carbon electrode suggest that very small particles are present at the electrode surface. On the other hand, the presence of submicrometric particles was found to be evident for Prussian Blue formed on the modified surface. In the case of the copper-modified electrode, stripping voltammetry was used to estimate the amount of metallic copper, which was found to be in reasonably good agreement with the XPS data.