Novel Zn-Al LDHs based S-scheme heterojunction with coral reef-like structure for photocatalytic activation of peroxymonosulfate towards nitenpyram decomposition

Abstract

The construction of an S-scheme heterojunction is an effective way to enhance the photocatalytic activity of composite materials. Thus, a co-precipitation method is combined with a hydrothermal synthesis method in this study to synthesize an S-scheme heterojunction of Bi2WO6/Ag3PO4/Zn-Al LDH photocatalyst with an exceptional morphology like a coral reef. On this basis, an AP0.5BWLDH0.3/PMS/Vis reaction system is constructed. The prepared Bi2WO6/Ag3PO4/Zn-Al LDH composites present better oxidation performance than pure Bi2WO6, Zn-Al LDH and Ag3PO4, with 100% Nitenpyram (50 mg/L) degraded within 90 min due to the photocatalytic activation of peroxymonosulfate. The significant increase in photocatalytic activity is not only due to the uniformly distributed coral reef-shaped nanostructures but also the extended life of the carrier with strong redox capability through S-scheme heterojunction. During the simulated exposure to sunlight, the internal electric field, optimized energy band structure, as well as coulomb force interaction all contributed to the promotion of the transportation of electron-hole pairs in the Bi2WO6/Ag3PO4/Zn-Al LDH composite. For this reason, electrons and holes have high reducing and oxidizing properties, which make the composites have high redox capacity. Then the radical trapping experiments, ESR testing and XPS analysis were used to verify these results. It was revealed that the S-scheme heterojunction mechanism was suitable for the electron migration in a photocatalyst. This study extends the design and preparation ideas of new S-scheme heterojunction photocatalysts and then proposes effective strategies to solve future water pollution.