Ag2S/TiO2 Z-scheme heterojunction under magnetic field: Enhanced photocatalytic degradation of tetracycline

Abstract

Multi-field assisted photocatalytic technology is an effective way to improve the photocatalytic performance of photocatalysts. Herein, we synthesized the Ag2S/TiO2 Z-scheme heterojunction photocatalyst and demonstrated the impacts of internal electric field (EF) and external magnetic field (MF) on the degradation of tetracycline (TC). Their structural, optical and electrochemical properties were characterized in detail. Ag2S/TiO2 demonstrated conspicuously enhanced photocatalytic activity towards the degradation of TC owing to the photosensitization of Ag2S and effective separation of charge carriers by forming an internal EF at the interface of the composite. Further, a higher degradation of TC (degradation conversion: 95.7% and TOC removal: 75.7%) was achieved by imposing the 1400 Gauss of an external MF and 500rpm. This is due to the high-rate charge carrier separation and migration caused by MF induced spin polarization and Lorentz force acting on charge carriers, accelerating TC degradation with lower active energy (MF: 33.18 KJ·mol-1 and NMF: 49.01 KJ·mol-1). Furthermore, Ag2S/TiO2 also demonstrated exceptional stability and reusability. The photocatalytic mechanism of Ag2S/TiO2 Z-scheme heterojunction under MF was discussed in detail based on the identification of the main reactive species (·OH and ·O2−) by radical trapping experiments and EPR analysis.