Activation of Peroxodisulfate Coupled with Photocatalysis by Pyrrolic N-Rich Fe-N4 Sites for High Efficiency Degradation of Tetracycline Hydrochloride

Photocatalysis is an efficient technology for the degradation of pollutants. However, there is still much room for improvement in its degradation efficiency. In this study, a pyrrolic N-rich g-C₃N₄ (PN-g-C₃N₄) framework was synthesized with transition metal M (M=Fe, Co, Ni, Cu, Cr, and Mn) atomic sites coordinated onto it. Then, a series of single atomic metals M anchored to PN-g-C₃N₄ (M/PN-g-C₃N₄) are constructed for peroxodisulfate activation. Their order of catalytic activity follows Fe>Cr>Ni>Cu≈Co>Mn, in particular the degradation rates of the TCH for Fe-PN-g-C₃N₄ are 3.74 times higher than that of undoped PN-g-C₃N₄. These carefully regulated pyrrolic N-rich Fe sites demonstrate outstanding performance in degrading organic pollutant. As an exemplary model, the Fe/PN-g-C₃N₄ catalyst efficiently drives the catalytic oxidation of TCH through Fenton-like reaction under visible light, showcasing exceptional cycle stability and a broad effective pH range of 3.0–11.0. The synergy between photocatalysis and Fe doped catalysis results in increased generation and separation of charge carriers, along with the cyclic transformation of the Fe³⁺/Fe²⁺ couple. This combination significantly enhances the Fenton-like performance, making it a highly effective process for pollutant degradation.