Facile construction of 2D g-C3N4 supported nanoflower-like NaBiO3 with direct Z-scheme heterojunctions and insight into its photocatalytic degradation of tetracycline

Photocatalytic oxidation using solar energy is a promising green technology to degrade antibiotic contaminants. Herein, a 2D g-C3N4 supported nanoflower-like NaBiO3 with direct Z-scheme heterojunction was synthesized via a facile hydrothermal approach, and the photocatalytic performance of g-C3N4/NaBiO3 was remarkable better than that of g-C3N4 and NaBiO3 for tetracycline degradation under visible light. Photoinduced electrons accumulated on the conduction band of g-C3N4 and holes gathered on the valence band of NaBiO3, which was more suitable for generating superoxide and hydroxyl radicals. Meanwhile, the built-in electric field between g-C3N4 and NaBiO3 was proved by their different work functions based on DFT calculations, which enhanced the charges separation. The formed radicals were determined by ESR, and their role in the degradation of tetracycline was examined by the active species trapping test. Moreover, the sites attacked by free radicals and degradation pathways for tetracycline were inferred by the results of Gaussian 09 program and HPLC-MS. The effects of water matrix and three other organic contaminants was further studied for actual use evaluation. Importantly, the prepared g-C3N4/NaBiO3 showed stable photodegradation activity for eight cycles. This work not only provides a promising photocatalyst, but also gets insight into the photocatalytic removal of tetracycline.