Photoelectrocatalysis/Photoelectro-Fenton Coupling for Methylparaben Degradation Using a TiO2 Nanotube Photoanode

We synthesized TiO 2 nanotubes by anodizing titanium and characterized them using micro-Raman spectroscopy, UV–Vis diffuse reflectance spectroscopy, and scanning electron microscopy. Electrochemical measurements were also performed to evaluate the photoelectrochemical properties of the TiO 2 nanotube electrodes. We investigated the photoelectro-Fenton/photoelectrocatalysis (PEF/PEC) system using the TiO 2 photoanode for the degradation and mineralization of methylparaben (MP) and compared it with the conventional PEF process using a boron-doped diamond (BDD) anode. Under identical operating conditions, the TiO 2 nanotube photoanode achieved nearly complete MP removal (99%) within 10 min and a mineralization current efficiency of 46% after 1 h, outperforming the BDD-based PEF system, which achieved 70% MP removal and 30% mineralization current efficiency under the same conditions. The enhanced performance of the TiO 2 -based system may reflect the simultaneous contribution of photoelectrochemical and Fenton-based oxidation pathways, with photogenerated charge carriers and hydroxyl-radical-mediated reactions potentially contributing to improved degradation and mineralization. However, this study did not directly determine the individual contribution of specific reactive species. The higher current efficiency obtained with the TiO 2 photoanode indicates more effective utilization of the applied electrical charge for mineralization. Overall, these findings highlight the potential of TiO 2 nanotube photoanodes as an efficient alternative to BDD electrodes for the electrochemical treatment of persistent organic pollutants.