Synthesis of S scheme 2D/2D g-CN/g-CN heterojunction with enhanced visible-light-responsive photocatalytic performance for photocatalytic degradation tetracycline: DFT analysis, degradation pathway and mechanism Insight

2D/2D g-C3N5/g-C3N4 heterojunction (CNH) is successfully synthetized for photocatalytic degradation of tetracycline (TC) from wastewater. CNH exhibits excellent photocatalytic activity for TC photocatalytic degradation with removal of 99.8% at N5/N4 mass ratio of 1.5, which has fast separation rate of the photogenerated carriers. The TOC mineralization rate of CNH (83.9%) is larger than that of the pure g-C3N4 and g-C3N5. The active group capture experiment analysis indicates that ·O2− plays a crucial role in TC degradation process. TC degradation mechanism analysis result indicates that CNH with π-π* electron delocalization superposition following S scheme charge transfer mechanism is constructed. Density functional theory calculation is also applied to further investigate TC degradation mechanism. TC photocatalytic degradation path is systemically analyzed by MS-UPLC technology. The TC removal is significantly inhibited by the CO32− and HCO3− compared to SO42− and the NO3−, which is also investigated in the river water and tap water. Besides, the CNH has good stability with removal of 93.8% after 5 cycles.