Dual-method construction of Bi5O7I/Bi2WO6 heterostructures for efficient photocatalytic degradation of oxytetracycline and bacterial inactivation

A Bi 5 O 7 I/Bi 2 WO 6 nanocomposite with hierarchical spherical structure was successfully prepared by co-precipitation and hydrothermal methods. Notably, the composite (denoted as BB-50) exhibited optimal photocatalytic performance when the Bi 5 O 7 I:Bi 2 WO 6 weight ratio was 50%, with the degradation rate of oxytetracycline (OTC) reaching 98.3% within 90   min and the inhibition rate of Escherichia coli ( E. coli ) bacteria reaching 100% within the same time frame. Characterization experiments and theoretical calculations indicated that the formation of the heterojunction induced an internal electric field at the interface, consistent with the transfer mechanism of photogenerated carriers characteristic of type-I heterojunctions. In addition, the formation of the Bi 5 O 7 I/Bi 2 WO 6 heterojunction promoted the generation of reactive oxygen species (ROS), including ·OH, h + , and e − . The formation of the Bi 5 O 7 I/Bi 2 WO 6 composite not only enhanced the light-absorption capacity (with a red-shift to 433   nm), but also greatly strengthened the adsorption ability, as the specific surface area of BB-50 was higher than those of the Bi 5 O 7 I and Bi 2 WO 6 components, respectively. In particular, the specific surface area of BB-50 was found to be 10.2 and 18.7 times higher than those of Bi 5 O 7 I and Bi 2 WO 6 , respectively. This complex effect also improved the separation and transfer efficiency of photogenerated carriers, which significantly enhanced the photocatalytic activity. The present composite exhibited considerable potential for the efficient removal of OTC and E. coli , providing a feasible approach for reducing water environmental pollution.