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. 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 hydroxyl radicals. 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 hydroxyl radicals. 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. Besides napropamide, 63 ± 2% and 54 ± 3% degradation were also obtained for glyphosate and atrazine by the PCM-HDA within 60 min at an applied potential of -0.146 V at pH ~7. The stability of the PCM-HDA electrode was demonstrated by the maintained ~80% napropamide degradation in six consecutive runs. Compared to conventional Fenton systems, the PCMs provide a simplified “one-stop” platform that overcomes the system complexity and pH limitation. In addition to herbicide degradation, the PCM-HDA electrode may also be used for the facile treatment of an array of relatively recalcitrant aquatic pollutants.

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

ACS Fall 2021

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