Covalent modification of glassy carbon electrode during electrochemical oxidation process of 4-aminobenzylphosphonic acid in aqueous solution

4-Aminobenzylphosphonic acid (4-ABPA) was covalently grafted on a glassy carbon electrode (GCE) through two types of reaction mechanisms viz. amine oxidation and the Kolbe-like reaction during the electrooxidation process in 0.1 M KCl aqueous solution. Two irreversible oxidation peaks were observed at about 0.75 and 0.90 V in cyclic voltammograms between 0.5 and 1.1 V. X-ray photoelectron spectroscopy (XPS) shows the presence of two types of N 1s environment after oxidation of 4-ABPA on the GCE surface. The quantum chemistry calculation proves that both of the NH2 and CH2 groups in 4-ABPA molecule can perform the oxidation reaction in turn. From this, we found and substantiated that the Kolbe-like reaction of benzylphosphonic acid group in 4-ABPA molecule can take place in aqueous solution.