Electrochemical Activity of Modified Glassy Carbon Electrodes with Covalent Bonds Towards Molecular Oxygen Reduction

The formation of covalent bonds on glassy carbon electrodes (GCEs) by producing oxidized functional groups (-COOH,-OH,-CHO, etc.) and using molecules such as 4-aminopyridine (4-AP), isonicotinic acid (IA) and 4-aminobenzoic acid (PABA) is proposed in this work with the aim of forming stable bonds. These modifications are done by using bulk electrolysis at an anodic fixed potential and by the Kolbe’s reaction. Then, these modified systems are probed towards dioxygen reduction and it is seen that the oxidized GCE is the most active system, while the GCE modified with PABA possesses the lowest activity towards the reduction of O2. By doing kinetic studies it was possible to calculate the transferred electrons and the Tafel slope for the most active system. In this sense, this reaction implies 2 transferred electrons and the Tafel slope has a value of 68 mV·decade-1 in the oxidized GCE. Finally, AFM studies were done in order to get information about the morphological behavior of these systems in which each one presents different roughness (Rq values)