Enhanced electrochemical activity of regenerated expanded graphite electrode after exhaustion in the process of phenol oxidation

The presented paper deals with the cyclic electrochemical oxidation of phenol occurring in alkaline solution on the electrode made of expanded graphite (EG). Passive oligomer layer produced on the electrode surface during the first cycle of phenol oxidation brings about a dramatic decrease in electrochemical activity of the EG anode in the subsequent cycles. It was shown that electrode spent during three cycles of phenol oxidation could be thermally regenerated at 400 °C to such an extent that its original electroactivity is significantly exceeded. The time of heat treatment exerts a strong influence on the properties of regenerated graphite. The increase in electrochemical activity of expanded graphite electrode after the regeneration process is attributed to enhanced activity of carbon–carbon composite formed due to carbonization of oligomer film covering the surface of exhausted graphite. The physicochemical features of the oligomer/EG composite were studied using electrochemical technique, scanning electron microscopy, thermal analysis, X-ray photoelectron spectroscopy (XPS) and BET measurements.