Electrochemical measurements of Cu²⁺ ions adsorbed on an electrochemically oxidized glassy carbon electrode

The adsorption of copper (II) ions with aqua ligands on a glassy carbon electrode was induced by electrochemically oxidizing the surface. Electrochemical characterizations of the adsorbed copper ions using cyclic voltammetry and chronocoulometry were performed. The adsorption kinetics and isotherm were estimated. The amount of adsorption was proportional to the background currents which increased with the degree of surface oxidation. To explain the adsorption of the copper ions onto the surface, an electrostatic interaction after the ion-exchange reactions was proposed. With increasing ionic strength or decreasing pH of the copper-containing solution for the adsorption, voltammograms with decreasing waves were obtained, which indicates that decreasing amounts of copper ions were adsorbed. From the sizes of the waves for the redox reactions of Cu²⁺ ions adsorbed in solutions containing some alkali metal cations, their relative adsorption strengths were estimated with the order of H⁺ >Li⁺ > Na⁺ > K⁺.