Construction of Au modified direct Z-scheme g-C3N4/defective ZnO heterostructure with stable high-performance for tetracycline degradation

Highlights: • Preparation of novel Z-scheme Au-g-C₃N₄/ZnO hierarchical heterojunction. • Synergistic effect of Z-scheme heterojunction, SPR and oxygen vacancies. • Au-g-C₃N₄/ZnO heterojunction owns unprecedented photocatalysis activity for TC. The residual antibiotics in water has become an environmental problem and is now deeply concerned. Z-scheme g-C₃N₄/defective ZnO heterojunction embellished with Au nanoparticles (Au-g-C₃N₄-ZnO) was synthesized by three sequential procedures, in-situ the preparation of g-C₃N₄, the guided cultivation of ZnO nanorods on g-C₃N₄ nanosheets and the deposition of Au nanoparticles. The tailored photocatalysts, imbuing with inherent oxygen vacancies and outstanding light absorption capacity, exhibits unprecedented photocatalysis efficiency for tetracycline (TC) degradation. The formed Au-g-C₃N₄-ZnO implements broad-spectrum response, intensifying capacity of light harvest and utilization and promoting the separation and transmission efficiency of carriers. Remarkably, the photocatalytic degradation for TC by 2%Au-g-C₃N₄-ZnO achieves the best degradation efficiency of 74.7% within 30 min under Xe lamp irradiation. It displays excellent stability and acid or alkaline resistance. Besides, the TC degradation pathways are elucidated in line with intermediate degradation products. Finally, a novel Z-scheme heterojunction photocatalytic mechanism is rationally proposed based on the band structure, surface plasmon resonance effect, oxygen vacancies, charge transfer behaviors and active species generation.