Fabrication of S-scheme ZnO/Zn_3(PO_4)_2 heterojunction photocatalyst toward photodegradation of tetracycline antibiotic and photocatalytic mechanism insight

摘要

In this work, a S-scheme ZnO/Zn-3(PO4)(2) heterojunction photocatalyst was fabricated by a simple co-precipitation manner under reflux condition. The ZnO/Zn-3(PO4)(2) heterostructured nanocomposite was employed for the degradation of tetracycline antibiotic under UV and visible light irradiation. The structure, composition, morphology, and optical properties of the as-synthesized ZnO/Zn-3(PO4)(2) products were characterized by XRD, EDS, FESEM, TEM, UV-Vis DRS, and PL measurements. The hybrid ZnO/Zn-3(PO4)(2) nanoparticles exhibited the highest photocatalytic efficiency in the degradation of tetracycline under ultraviolet (97) and visible (82) light irradiation, which was similar to 1.5 times more than sole Zn-3(PO4)(2) nanostructures. The promoted light harvesting and generated heterojunction interfaces between ZnO and Zn-3(PO4)(2) can obviously reduce the recombination rate of charge carriers in the ZnO/Zn-3(PO4)(2) heterostructure. Moreover, a reasonable photocatalytic mechanism of the UV and visible light-induced degradation of antibiotic over ZnO/Zn-3(PO4)(2) nanocomposites is suggested. The results indicated that under UV, the mechanism follows from the S-scheme in the presence of O-center dot(2)- and (OH)-O-center dot as predominant species, while upon visible, the type-II heterojunction utilizing O-center dot(2)- as prevailing radical is possible.