Construction of Direct Z-Scheme AgI/Bi₂Sn₂O₇ Nanojunction System with Enhanced Photocatalytic Activity: Accelerated Interfacial Charge Transfer Induced Efficient Cr(VI) Reduction, Tetracycline Degradation and <i>Escherichia coli</i> Inactivation

Abstract

The exploration of highly efficient visible light driven photocatalysts for diverse pollutants removal has received great concerns in wastewater treatment. Here, a series of tightly connected AgI/Bi2Sn2O7 nanocomposites were fabricated through an in situ deposition–precipitation route. The resulting AgI/Bi2Sn2O7 photocatalysts exhibited superior photocatalytic performance for Cr(VI) reduction, tetracycline (TC) degradation as well as Escherichia coli (E. coli) inactivation. It was found that AB-31.97 nanocomposite displayed optimal photocatalytic performance under visible light irradiation, i.e., nearly 100% reduction of Cr(VI) and 7.48-log inactivation of E. coli cells. As for TC, the overall degradation process was reflected by three-dimensional excitation–emission matrix fluorescence spectra (3D EEMs), and the detailed degradation pathways were proposed through LC-MS system. The promoted photocatalytic performance of the obtained AgI/Bi2Sn2O7 nanocomposites can be attributed to the formed nanojunction structure between AgI and Bi2Sn2O7, which not only accelerates the interfacial charge transfer efficiency but also preserves the strong redox ability of the photogenerated electrons and holes. Meanwhile, cycling experiments and inductively coupled plasma mass spectroscopy (ICP-MS) measurement manifested that AB-31.97 nanocomposite also presented outstanding photostability. According to the results of radical trapping experiments and electron spin resonance (ESR) detection, h+, e–, ·O2– and ·OH all involved in photocatalytic reaction. Based on the experimental results, a plausible Z-scheme charge transfer mechanism was put forward. This work provides a deep insight into the multiapplication of nanojunction photocatalysts and highlights a facile way to construct highly efficient photocatalysts for wastewater treatment.