Boron Bifunctional Catalysts for Rapid Degradation of Persistent Organic Pollutants in a Metal-Free Electro-Fenton Process: O2 and H2O2 Activation Process

Metals usually served as the active sites of the heterogeneous bifunctional electro-Fenton reaction, which faced the challenge of poor stability under acidic or even neutral conditions. Exploring a metal-free heterogeneous bifunctional electro-Fenton catalyst can effectively solve the above problems. In this work, a stable metal-free heterogeneous bifunctional boron-modified porous carbon catalyst (BTA-1000) was synthesized. For the BTA-1000 catalyst, the yield of H₂O₂ (294 mg/L) significantly increased. The degradation rate of phenol by BTA-1000 (0.242 min^-1) increased by an order of magnitude, compared with the porous carbon catalyst (0.0105 min^-1). The BTA catalyst could rapidly degrade industrial dye wastewater, and its specific energy consumption was 5.52 kW h kg^-1 COD^-1, lower than that in previous reports (6.38-7.4 kW h kg^-1 COD^-1). DFT and XPS revealed that C═O and -BC₂O groups jointly promoted the generation of H₂O₂, and the -BCO₂ group played dominant roles in the generation of ^•OH because the oxygen atom near the electron-giving groups (-BCO₂ group) facilitated the formation of hydrogen bond and H₂O₂ adsorption. This work gained deep insights into the reaction mechanism of the boron-modified porous carbon catalyst, which helped to guide the development of metal-free heterogeneous bifunctional electro-Fenton catalysts.