Effect of dye chemical structure on the efficiency of photoassisted electrochemical degradation using a cathode containing carbon nanotubes and a Ti/RuO₂ anode

Abstract In this research, photoassisted electrochemical degradation of 13 commercial dyes with various chemical structures and substituent groups was investigated using a cathode containing carbon nanotubes (CNTs) and a titanium/ruthenium oxide (Ti/RuO₂) anode. The inner and outer diameters of the CNTs and their stabilization on carbon paper support were confirmed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. All experiments were carried out in identical operating conditions using a recirculation system under ultraviolet (UV) light irradiation. The dyes with electron-releasing groups (e.g., amino, hydroxyl, and acetamido) were more degraded than those containing electron-withdrawing groups (e.g., sulfo, sulfonyl, and halo) due to inductive and/or resonance effects. Moreover, the obtained results reveal that the degradation process follows pseudo-first-order kinetics, and the degradation efficiency was evaluated as the electrical energy per order.