A Novel Bismuth-Rich Bi₃O₄Cl/Bi_xO_yI _z Composite with Intensified Photocatalytic Internal Electrical Field for Photocatalytic Degradation of Antibiotics

The enhancement of photocatalytic semiconductor degradation performance through a bismuth-rich strategy and heterojunction engineering is considered a very effective approach. Herein, the bismuth-rich Bi3O4Cl/BixOyIz composites are synthesized through a simple solvothermal reaction. The composites have an internal electric field because of their specific layered structure. Due to the difference between their covalent [BixOy](2+) layer and exchangeable halogen ion layer, the enhanced internal electric field facilitates electron transfer at the high-quality interface of the semiconductor. The trace presence of Bi3O4Cl/BixOyIz (0.1 g L-1) can achieve an 88% removal of tetracycline (20 mg L-1) from the solution phase under visible light illumination in 120 min. The photocatalytic activity is much higher than that of pure BiOCl and BiOI. Furthermore, the material also exhibits high photocatalytic degradation performance for bisphenol A, doxycycline hydrochloride, etc. The excellent results further confirm the application range of the prepared photocatalysts. The superior photocatalytic activity of Bi3O4Cl/BixOyIz is attributed to the formation of a heterojunction and the generation of an internal electric field, which enhances charge separation and oxidation ability. Photoelectrochemical characterization can confirm the above views. Free radical trapping experiments and electron spin resonance show that heterojunctions can produce abundant center dot O-2(-) and center dot OH under visible light irradiation.