Z-scheme g-C3N4/ZnS heterojunction photocatalyst: One-pot synthesis, interfacial structure regulation, and improved photocatalysis activity for bisphenol A

Taguchi experiment was used to optimize the experimental conditions, including the dosage of precursor and calcination temperature, in order to controllably synthesize g-C3N4/ZnS heterojunction composites from zinc acetate (Zn(OAc)2) and thiourea (Tu) by facile one-pot annealing method. The photocatalytic activity of g-C3N4/ZnS heterojunction composites for bisphenol A (BPA) in aqueous solution was studied. The g-C3N4/ZnS composites prepared at the optimum conditions according to the results of Taguchi experiment (labeled as g-C3N4/ZnS-10) exhibited significantly improved removal rate of BPA (92.1% after 8 h), which was 7.4, 2.1 and 6.6 times higher than that of g-C3N4, ZnS and g-C3N4/ZnS-1 (the composites with the lowest photocatalytic activity in Taguchi experiment), respectively. g-C3N4/ZnS heterojunction composites was characterized by XRD, FT-IR, BET, SEM, TEM, EDS, XPS, PL, EPR, UV–vis DRS and UPS. The trapping experiment and DMPO spin-trapping experiment revealed that Superoxide radicals played a major role in the photocatalysis of BPA. The excellent photocatalytic activity of g-C3N4/ZnS-10 was mainly attributed to the synergistic effect which can create the internal driving force to enhance the light response and improve the separation/transfer efficiency of interfacial charge in Z-scheme heterojunction. The underlying photocatalytic mechanism was discussed and analyzed in details.