Facile construction of 2D g-CN supported nanoflower-like NaBiO 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-CN supported nanoflower-like NaBiO with direct Z-scheme heterojunction was synthesized via a facile hydrothermal approach, and the photocatalytic performance of g-CN/NaBiO was remarkable better than that of g-CN and NaBiO for tetracycline degradation under visible light. Photoinduced electrons accumulated on the conduction band of g-CN and holes gathered on the valence band of NaBiO, which was more suitable for generating superoxide and hydroxyl radicals. Meanwhile, the built-in electric field between g-CN and NaBiO 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-CN/NaBiO 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.