Graphitic carbon nitride coupled with molybdenum selenide composite photocatalyst for tetracycline degradation

In this work, we report a novel, simple, and efficient molten salt-modified graphitic carbon nitride coupled with molybdenum selenide composite photocatalyst (g-C3N4 @MoSe2) with strong stability and enhanced degradation of tetracycline (TC) under visible light (removal rate > 99%, within 1 h). The synthesized catalyst has strong stability. X-ray diffraction (XRD), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR) tests confirmed the successful synthesis of the catalysts, and possible energy band structures were inferred using ultraviolet photoelectron spectroscopy (UPS) and ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS) tests. Photoelectrochemical and photoluminescence (PL) measurements confirmed that the g-C3N4 @MoSe2 composite possesses a smaller charge-transfer resistance, a higher photocurrent density, and a lower complex efficiency of photogenerated carriers than that of pure g-C3N4 or MoSe2, which are the prerequisites for improving its catalytic efficiency. Through band structure analysis, an S-scheme heterojunction can be formed between g-C3N4 and MoSe2, and more ⋅O2− and h+ species generated on the conduction band and valence band of the composite catalyst, which is the main reason for the enhanced redox ability of g-C3N4 @MoSe2.