Mesoporous Ultrathin g‐C 3 N 4 with Surface Defects Activates Peroxodisulfate for Tetracycline Removal under Visible Light: Synergy and Mechanism

Metal‐free catalysts combined with a persulfate‐based advanced oxidation process (PS‐AOP) are considered to be a promising purification technology. In this study, porous thin layers of g‐C 3 N 4 with nitrogen defects are synthesized by a simple method. Multiple characterization methods demonstrate the porous thin layer structure and the N defects of P‐CN x ‐1. Photoelectrochemistry tests show that the combination of morphological modulation and defect engineering produces an excellent photocurrent response. The P‐CN x ‐1/PS/Vis system shows the best tetracycline (TC) removal efficiency degrading 74.2% of TC within 90 min, and the degradation kinetics are significantly improved. Optimal degradation conditions such as catalyst dosage, persulfate (PS) dosage, initial TC concentration, and initial pH are investigated. Cyclic and anionic experiments demonstrate the excellent stability of P‐CN x ‐1 and its ability to treat complex aqueous bases. Mechanistic experiments show that ˙ OH/SO 4˙ − / ˙ O 2 − /h + / 1 O 2 are all involved in the degradation of TC. Liquid chromatography‐mass spectrometry (LC‐MS) suggests possible degradation pathways for TC. This work aims to provide new ideas for the application of metal‐free g‐C 3 N 4 in PS activation.