Enhanced photocatalytic degradation of tetracycline under visible light by using a ternary photocatalyst of Ag3PO4/AgBr/g-C3N4 with dual Z-scheme heterojunction

A ternary dual Z-scheme heterojunction photocatalyst composed of Ag 3 PO 4 , AgBr and g-C 3 N 4 was prepared by a facile chemical deposition method. Scanning electron microscope equipped with energy-dispersive X-ray, X-ray diffraction, diffusive reflective spectrophotometry and X-ray photoelectron spectroscopy were carried out to characterize the morphology, element and structure properties of the photocatalysts. The photocatalytic activity was evaluated by the photoelectrochemical tests and the degradation of tetracycline (TC). The results indicated that the composite Ag 3 PO 4 /AgBr-20%g-C 3 N 4 exhibited the best photocatalytic activity in terms of the photocurrent response and the degradation of TC under visible light irradiation. The degradation rate of TC over the ternary photocatalyst was 0.12 min −1 , which was 2.55 and 3.24 times faster than that over Ag 3 PO 4 /AgBr and Ag 3 PO 4 , respectively. During photocatalysis, metallic Ag could be formed and served as the electron transfer mediator to build the dual Z-scheme heterojunction by bridging the recombination of electrons and holes. By this manner, more efficient separation of photo-generated carriers and better redox ability could be obtained, consequently promoting the photocatalytic activity. Additionally, the trapping experiments verified that O 2 − and h + played prominent roles in the photocatalytic processes, while the impact of OH on the removal efficiency was relatively small.