Activated CdS/ sulfur doped g-C₃N₄ photocatalyst for dye and antibiotic degradation: Experimental and DFT verification of S-scheme heterojunction

To alleviate situation caused by azo dyestuff and antibiotics, a series of CdS/sulfur doped carbon nitride (GCNS) S-scheme heterojunction photocatalysts have been successfully fabricated by a pretty facile solid-state diffusion (SSD) method,. Under visible light, the optimal sample called CdS/GCNS-1:2 presented the best photodegradation rate of nearly 100% over methyl orange (MO), of which the reaction constant k was about 9.67 and 5.39 times higher than that of pure GCNS and CdS, respectively. Degradation rate of 91% over tetracycline hydrochloride (TCH) was achieved within 60 min as well. The DFT calculations, XPS and charge flow tracking tests clarified the surge of C-S linkages and the construction of interfacial S-scheme heterojunction. The former promoted the fixation and conversion of adsorbed oxygen, while the latter accelerated the separation/transport of charge carriers. These tuning eventually collaborates on the promotion of •O₂⁻ reactive species, which confirmed as the predominant role of photoreaction. Furthermore, the plausible degradation pathways of MO/TCH and photocatalytic optimization mechanism were thoroughly elucidated.