Boron Bifunctional Catalysts for Rapid Degradation of Persistent Organic Pollutants in a Metal-Free Electro-Fenton Process: O and HO 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 HO (294 mg/L) significantly increased. The degradation rate of phenol by BTA-1000 (0.242 min) increased by an order of magnitude, compared with the porous carbon catalyst (0.0105 min). The BTA catalyst could rapidly degrade industrial dye wastewater, and its specific energy consumption was 5.52 kW h kg COD, lower than that in previous reports (6.38-7.4 kW h kg COD). DFT and XPS revealed that C═O and -BCO groups jointly promoted the generation of HO, and the -BCO group played dominant roles in the generation of OH because the oxygen atom near the electron-giving groups (-BCO group) facilitated the formation of hydrogen bond and HO 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.