In situ electrogeneration and activation of H2O2 by atomic Fe catalysts for the efficient removal of chloramphenicol.

Heterogeneous electron-Fenton processes have been regarded as promising, environmentally friendly techniques for the removal of refractory organics. A new strategy has been brought forward for an electron-Fenton-like process with in situ H2O2 production, but regarding the catalysts, their geometric stability, H2O2 selectivity, and applicability under high pH values still need to be improved. Herein, bifunctional catalysts were proposed for a heterogeneous Fenton-like reaction by introducing Fe atoms into defect-enriched graphene sheets (Fe/N-DG). The structural and compositional results suggested that the excellent dispersing stability of Fe atoms is mainly attributed to the abundant pyridinic-N sites. Optimized Fe1/N-DG exhibited superior mass activity (5.28 A mgFe-1 at 0.6 V vs. RHE) and H2O2 selectivity (86%) under the synergistic effects of Fe‒N and Fe‒O sites. The Fe/N-DG catalysts maintained superior activities for chloramphenicol removal, even under extreme pH conditions (pH≤4 or pH≥10). Of these catalysts, Fe1/N-DG with a predominant Fe-N structure exhibited the best catalytic performance, achieving the complete removal of chloramphenicol within 180 min under alkaline conditions. The possible mechanism for chloramphenicol removal under alkaline conditions was proposed, along with those for the production and activation of H2O2. This study gives new insights into atomic Fe-based catalysts exhibiting excellent selectivity and stability for antibiotic wastewater treatment.