Halogen-Doped Hydrothermal Carbonation Carbon Photocatalytic Activation of Persulfate for Thiamethoxam Degradation: Halogen Doping Enhances Light Absorption

The efficient decontamination of water containing thiamethoxam (THM) is difficult due to its chemical stability. Herein, a series of halogen-doped hydrothermal carbonation carbons (X-HTCC, X = I, Cl, and Br) are synthesized via a one-pot hydrothermal route with glucose as the precursor and employed for the photocatalytic activation of persulfate (PS) toward the degradation of THM in aqueous solution. Among them, I-HTCC shows excellent degradation properties, achieving a 93.4% THM degradation rate within 240 min under visible-light irradiation (I-HTCC/PS/VIS), and retains a 75% degradation rate after five cycles. Mechanistic studies reveal that halogen doping enhances light harvesting and facilitates photogenerated electron transfer to PS, effectively suppressing electron–hole recombination while generating SO4•–, thereby endowing a synergistic effect between photocatalysis and radical oxidation. Additionally, a possible reaction pathway for the degradation of THM by the X-HTCC/PS/VIS reaction system is elucidated. This study provides a way to design high-performance water treatment catalysts.