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

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.