Photo-Fenton degradation of emerging pollutants over Fe-POM nanoparticle/porous and ultrathin g-C3N4 nanosheet with rich nitrogen defect: Degradation mechanism, pathways, and products toxicity assessment

Surface defect engineering has been suggested as an effective strategy to enhance photo-Fenton degradation performance. However, the underlying impact mechanism remains unknown. This study precisely constructed an efficient photo-Fenton catalyst through self-assembly of Fe-polyoxometalates nanoparticles on porous and ultrathin g-C3N4 nanosheets with nitrogen vacancies (Fe-POM/CNNS-Nvac). These nitrogen vacancies promoted photo-Fenton reaction rate constant for tetracycline hydrochloride (TCH) from 0.0950 to 0.1520 min−1 under visible light irradiation. Scavenging experiments and characterization results indicated that nitrogen vacancies could accelerate Fe(III)/Fe(II) conversion for OH and 1O2 generation, and directly regulate electronic structure for O2− generation. The possible degradation pathways of TCH were interpreted using experimental results and frontier electron density calculations. The results indicated that holes (h+) were responsible for ring-opening and 1O2/OH/O2− contributed to demethylation, deamination, and further mineralization. This study provides novel insight for the design of highly efficient catalysts with nitrogen vacancies for the removal of emerging pollutants.