Coexisting single-atomic Fe and Fe2O3 on nitrogen-deficient g-C3N4 with enriched Fenton-like oxidation and photocatalytic performances for tetracycline degradation: DFT calculation, degradation mechanism and toxicity evaluation

The regulation of heterogeneous material properties to strengthen the peroxymonosulfate activation to destroy refractory pharmaceuticals remains a challenge. Herein, a promising nitrogen-deficient catalyst (FeCN) with single atom Fe and Fe 2 O 3 nanoparticles dispersing on g -C 3 N 4 matrix was synthesized and applied as a competent peroxydisulfate (PDS) activator for tetracycline (TC) degradation under visible light. The K-edge X-ray absorption fine structures and 57 Fe Mössbauer measurements confirmed the unique configuration of Fe 2 O 3 and single atom Fe active sites (pyrrolic and pyridinic FeN 4 ) induced by the neighbouring nitrogen vacancies. The theory calculations and experiments provided a deep insight into the PDS activation and TC degradation via radical and non-radical pathways. The pyrrolic FeN 4 active sites dominated the electron transfer, while the pyridinic FeN 4 and Fe 2 O 3 decomposed PDS to produce free radicals. The synergistic effect between the Fenton-like oxidation and photocatalysis is responsible for efficient TC degradation. This study offers a new strategy by integrating novel catalysts and advanced oxidation technology for effective wastewater purification.