Well-dispersed iron and nitrogen co-doped hollow carbon microsphere anchoring by g-C3N4 for efficient peroxymonosulfate activation

Abstract

Developing single-atom Fenton-like catalysts with the maximum utilization of active sites present an attractive potential in environmental remediation. Herein, the single-atom Fe and N co-doped hollow carbon microsphere loaded g-C₃N₄ catalyst (HFeNC-g-C₃N₄) was prepared by an innovative cascade anchoring strategy using polystyrene as the hard template, iron phthalocyanine, polydopamine and urea as the Fe, N and C precursor, in which the in-situ generated g-C₃N₄ could not only effectively anchor Fe atom to create the well-dispersed Fe-N_x active sites, but also accelerate the electron transfer in peroxymonosulfate (PMS) activation. Taking advantages of such sequential protecting strategy, the as-synthesized HFeNC-g-C₃N₄ catalyst with single-atom Fe-N_x active sites, verified by XRD, XPS and HAADF-STEM, could work as an efficient Fenton-like catalyst for PMS activation, which achieved almost 100% removal of 4-chlorophenol (4-CP) in 5 min with the turnover frequency calculated to be 34.6 times higher than that of the homogeneous Fe²⁺ catalyst. The mechanism of O₂^•- dominated radical combined with nonradical ¹O₂ pathway was confirmed by quenching experiments and ESR analysis, which might be interrelated to the improvement of pH adaptability and interference immunity of HFeNC-g-C₃N₄/PMS system. Overall, the present findings provided an innovation strategy for the synthesis of excellent single-atom Fe based catalyst in wastewater purification.

Keywords: Cascade anchoring; Fe-N(x) active sites; Organics degradation; Peroxymonosulfate activation; Single-atom catalysis.