Rapid tetracycline degradation by S-scheme Se/g-C₃N₄ heterostructure

This research presents an efficient and stable photocatalyst for the removal of hospital pollutants, characterized by a rapid reaction rate and a cost-effective, straightforward synthesis process. The study focuses on enhancing the photocatalytic performance of graphitic carbon nitride (g-C₃N₄, abbreviated as g-CN) through selenium (Se), leading to the formation of Se/g-CN nanocomposites. These nanocomposites were synthesized via a sintering method in a tube furnace, with varying selenium concentrations (5%, 10%, and 15% of Se/g-CN ratio). X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirmed the formation of a heterostructure between Se and g-CN. Field emission scanning electron microscopy (FESEM) images revealed that selenium incorporation altered the porous morphology of pristine g-CN, transforming it into a flake-like structure in the Se/g-CN nanocomposites. Tetracycline (TC) antibiotic was used as the target pollutant, with the Se(10%)/g-CN nanocomposites achieving 96% degradation under 60 min of commercial, low-power light-emitting diode (LED) irradiation. Additionally, the Se/g-CN heterostructures demonstrated stable photocatalytic activity, maintaining their performance after four cycles of reuse. Band structure calculations indicated that Se/g-CN forms an S-scheme heterostructure, where photogenerated electrons in g-CN act as reducing agents, and photogenerated holes in Se function as oxidizing agents.