Promoted electro-Fenton degradation of norfloxacin by oxygen vacancy-modified titanium dioxide anode

Anodic oxidation-assisted cathodic electro-Fenton (AO-EF) is an effective technique for removing contaminants in wastewater as the coexistence of anodic oxidation and cathodic electrosynthesis of hydrogen peroxide (H₂O₂). In this work, an oxygen vacancy-modified titanium dioxide (O_v-TiO₂) anode was fabricated and constructed an AO-EF system with a fluorine-doped porous carbon (FPC) cathode that possesses high H₂O₂ electrosynthesis activity. The AO-EF system exhibits rapid norfloxacin degradation efficiency with a first-order kinetic rate constant of 1.12 min^-1, which is 1.6 and 44.8 times higher than those of single electro-Fenton (0.68 min^-1) and anodic oxidation (0.025 min^-1) processes, respectively. The boosted degradation ability of AO-EF system is attributed to the incorporation of oxygen vacancy into TiO₂ anode, which not only improves the oxidation capacity of TiO₂ but also acts as an active site for catalyzing H₂O₂ to produce hydroxyl radical (•OH). Benefiting from high •OH concentration, the AO-EF system is efficient for treating actual wastewater, and the chemical oxygen demand (COD) of pharmaceutical wastewater reduces from 780 to 42 mg/L within 4 h of treatment. The energy consumption is calculated to be 8.8 kWh/(kg COD), which is much lower than that of the EF system when treating the wastewater with similar COD values. This work offers novel perspectives on the development of energy-efficient synergistic electrocatalytic strategies for the effective degradation of persistent pollutants.