Fe3O4 nanoparticles encapsulated in boron nitride support via N-doped carbon layer as a peroxymonosulfate activator for pollutant degradation: Important role of metal boosted C–N sites

Developing highly efficient and stable catalysts for peroxymonosulfate (PMS) based advanced oxidation processes (AOPs) are crucial in the field of environmental remediation. In this work, a facile encapsulated-precursor pyrolysis strategy was reported to prepare a competent PMS-activation catalyst, in which uniformly distributed Fe3O4 nanoparticles were firmly anchored on porous boron nitride (BN) nanosheets by N-doped carbon shell (NC layer). Taking advantage of strong metal-support interaction, the as-synthesized catalyst (BFA-500) could efficiently activate PMS to achieve 100% removal of 4-chlorophenol (4-CP) in 6 min, and the corresponding turnover frequency (TOF) value was 1-2 orders of magnitude higher than that of the benchmark homogeneous (Fe2+) and nanoparticle (Fe0 and Fe3O4) catalysts. Moreover, the well protected encapsulated structure of BFA-500 ensured the remarkable stability that could effectively resist the interference of complex water environment, including initial pH value, various inorganic ions and actual water, and its catalytic activity remained almost unchanged in 5 use-regeneration cycles. More importantly, the generation of O2•- and 1O2 radicals for the 4-CP removal in BFA-500/PMS system was ascribed to Fe3O4 boosted C-N sites containing pyridinic N, where electrons transferred from the embedded Fe3O4 nanoparticles to C-N sites to secure the PMS dissociation into reactive radicals. Overall, this work provided a promising way to design desired PMS-activation catalyst toward wastewater purification.