A 1O2-dominated metal-free electro-Fenton floating system for water decontamination

Abstract

The heterogeneous electro-Fenton (EF) process encounters major obstacles, such as high costs and the risk of secondary pollution. Herein, we proposed a metal-free EF system utilizing a cost-efficient floating electrode composed of boron-modified acetylene black (BAB). The system enhanced H₂O₂ production and promoted the generation of reactive oxygen species (ROS), effectively degrading bisphenol A (BPA). The floating cathode promoted the natural oxygen diffusion to the reaction interface, removing the requirement for pumping oxygen or air. Moreover, this system enhanced H₂O₂ production 8-fold (451.25 mg/L) compared to conventional vertical mode. Singlet oxygen (¹O₂) was found to be the key ROS during BPA degradation, contributing 50.82%, while hydroxyl radicals (•OH) and superoxide radicals ($$) contributed 28.62% and 20.55%, respectively. The long lifetime and environmental interference resistance of ¹O₂ were effectively utilized. Theoretical models and experiments indicated that the -BC₂O group promoted H₂O₂ generation, while the -BC₃ group facilitated the production of •OH and the interconversion between •OH, $$, and ¹O₂. Additionally, the system maintained stable catalytic efficiency over an extensive pH range (3-11). Furthermore, the BAB-70 electrode required a cost of approximately $9.2×10^-5 for H₂O₂ production at a rate of 1 mg/L, representing a reduction of 11-fold to 4865-fold compared to the electrodes reported in previous studies. The study demonstrates an innovative strategy for advancing electrochemical water treatment by rationally combining ROS modulation with reactor configuration optimization, enabled by cost-effective electrode fabrication.