DFT and experimental study on photocatalytic degradation of tetracycline by Sulfur-doped monolayer g-C3N4 as a peroxymonosulfate activator

Doping enhances the activation of peroxymonosulfates (PMS) by metal-free carbon materials, addressing their inherent limitations in performance. In this study, experimental and theoretical calculations are combined to carry out the study of efficient activation of PMS for tetracycline degradation based on sulfur-doped g-C3N4 (SCN) as a promising photocatalyst. Calculation of the energy band structure, electronic and optical properties by density-functional theory methods suggests that doping results in a smaller band gap, smaller bond populations, and work function, leading to a redistribution of charges and dipoles at the g-C3N4 interface with a better ability to separate photogenerated h+/e- pairs. Meanwhile, the characterization and catalyst activity measurements indicate that doping improves the photocatalytic activity, which is in agreement with the theoretical calculations. In particular, the SCN synthesized at 1:1 ratio exhibited the best catalytic activity, and the degradation efficiency of TC within 2 h could reach 89.4 %. This study provides a highly effective metal-free carbon activator for the degradation of antibiotics from wastewater by PMS.