Single iron atoms embedded in MOF-derived nitrogen-doped carbon as an efficient heterogeneous electro-Fenton catalyst for degradation of carbamazepine over a wide pH

Developing efficient, stable heterogeneous catalysts with wide adaptability to pH is of great significance for the degradation of organic pollutants by electro-Fenton (EF). In this work, a novel heterogeneous EF (Hetero-EF) catalyst, single atomic Fe sites embedded into N-doped porous carbon (Fe-N/C) was prepared using Fe-doped zeolitic imidazolate frameworks as a precursor. Single Fe atoms anchored on N/C were clearly observed by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Due to the single-atom dispersion and the highest content of FeNx, the optimized 0.3Fe-N/C exhibited excellent catalytic activity for the removal of carbamazepine (CBZ) over a wide pH between 3∼11 with very low iron leaching (<0.3 mg/L even at pH 3). The turnover frequency in the Hetero-EF process was 1.6–19 times higher than that of most catalysts in literature. Besides, 0.3Fe-N/C showed superior durability in seven cycling tests and wide suitability to various pollutants. The quenching experiments and electron paramagnetic resonance demonstrated that both OH and 1O2 were responsible for the CBZ degradation, which made 0.3Fe-N/C had a strong tolerance to pH. This work provides a new perspective for the application of atomic Fe-based catalysts, improving stability and pH adaptability in Hetero-EF for wastewater treatment.