The facile synthesis of a single atom-dispersed silver-modified ultrathin g-C3N4 hybrid for the enhanced visible-light photocatalytic degradation of sulfamethazine with peroxymonosulfate

Abstract

Enabling the optimal usage of solar energy is considered to be one of the most pressing challenges in the photocatalytic remediation of water resident contaminants. Herein, a single-atom dispersed Ag loaded ultrathin g-C₃N₄ hybrid (AgTCM/UCN) was prepared through a facile co-polymerization of dicyandiamide with silver tricyanomethanide (AgTCM) and NH₄Cl, and used as a visible light driven photocatalyst for the degradation of sulfamethazine (SMT) in the presence of peroxymonosulfate (PMS). Under UV light, visible light and simulated sunlight irradiation, the AgTCM/UCN/PMS process showed higher efficiency for SMT degradation than AgTCM/UCN, UCN/PMS, and g-C₃N₄/PMS systems. This enhanced photocatalytic activity may be attributed to the synergistic effects encompassing the surface plasmon resonance (SPR) of Ag, high surface area of UCN, and efficient charge separation of PMS. Electron–spin resonance (ESR) and reactive species (RSs) scavenger-quenching experiments revealed that SO₄˙⁻ was generated following the addition of PMS, whereas O₂˙⁻ and h⁺ were predominantly responsible for the degradation of SMT. Three degradation pathways of SMT were deduced, including the cleavage of sulfonamide bonds, SO₂ extrusion, and the oxidation of the aniline moiety, based on mass spectrometry and theoretical calculations. The degradation of SMT in ambient water revealed that the AgTCM/UCN/PMS photocatalytic process can be efficaciously applied for the remediation of SMT contaminated natural waters, particularly sea water.