Regulating the Anodic Catalytic Selectivity in Electro-Fenton Process for Enhanced Pollutant Removal

Abstract

Owing to its simplicity, remarkable mineralization efficiency, and eco-friendly characteristics, the electron-Fenton (EF)-based advanced oxidation process is recognized as an effective technology to remove refractory organic pollutants. However, this technology is still limited by a narrow pH operation and low current efficiency due to the unsatisfactory activity and concomitant competing reactions on the electrodes. Herein, we demonstrate the versatility of regulating the water oxidation selectivity on the anode in the EF system to enhance the removal efficiency for pollutants with broadened pH range and improved current efficiency. With a homemade iron–carbon-based catalyst (Fe/C) as a cathode, commercial TiO2 (two-electron water oxidation) or RuO2 (four-electron water oxidation) as the anode, and rhodamine B (RhB) as the pollutant, the degradation efficiency values of both TiO2–Fe/C and RuO2–Fe/C are higher than that of conventional Pt–Fe/C with/without aeration, respectively. Specifically, the removal ratio for RhB in TiO2–Fe/C could reach 84.3% and 67.1% within 3 min at pH 3.0 and 7.0 with O2 aeration as compared to that of 56.7% and 45.6% for the Pt–Fe/C system. Without O2 aeration, the removal ratio for RhB in RuO2–Fe/C could reach 67.1% and 45.3% within 3 min at pH 3.0 and 7.0, while the values were 51.6% and 21.2% for the Pt–Fe/C. Furthermore, the H2O2 accumulation indicated that the two-electron water oxidation on the TiO2 could further increase the total concentration of H2O2. The four-electron water oxidation on the RuO2 could supplement O2 for the cathodic reduction to maintain the concentration of H2O2 during the electrolysis, leading to enhanced removal efficiency. Herein, based on the regulation of the water oxidation reaction in the anode, we propose an anodic optimized strategy to upgrade the EF-related processes.