Porous carbon monoliths for electrochemical removal of aqueous herbicides by "one-stop" catalysis of oxygen reduction and H₂O₂ activation

The overuse of herbicides has posed a threat to human health and the aquatic environment via DNA mutations and antibiotic gene resistance. Carbon-based cathodic electrochemical advanced oxidation has evolved as a promising technology for herbicide degradation by generating hydroxyl radicals (•OH). However, conventional electro-Fenton process relies on interaction of multiple species that adds to the system complexity and cost and narrows the working pH range. Herein, a series of porous carbon monoliths (PCMs) were developed as a "one-stop" platform for catalysis of the 2-electron ORR coupled with further catalytic reductive cleavage of H₂O₂ to produce •OH. A PCM prepared using 1,6-hexamethylene diamine (denoted as PCM-HDA) produced H₂O₂ at a level that was 374% higher than that obtained using commercially available carbon black at circum-neutral pH. Meanwhile, the generated H₂O₂ was catalytically decomposed to produce •OH. Based on these results, the PCM-HDA electrode achieved an 80 ± 2% degradation of napropamide in 60 min over the pH range of 4–10 at a mildly reducing potential, with a 69 ± 2% TOC reduction at circum-neutral condition in 2 h. This simplified system overcomes the system complexity and pH limitation of the conventional electron-Fenton processes.