Visible light-driven photocatalytic degradation of organic pollutants by a novel Ag3VO4/Ag2CO3 p–n heterojunction photocatalyst: Mechanistic insight and degradation pathways

Abstract

In the field of photocatalysis, the construction of a heterojunction system with efficient charge separation at the interface and charge transfer to increase the photocatalyst performance has gained considerable attention. In this study, the Ag 3 VO 4 /Ag 2 CO 3 p–n heterojunction is first synthesized using a simple co-precipitation method. The composite photocatalyst with a p-n heterojunction has a strong internal electric field, and its strong driving force can effectively solve the problem of low separation and migration efficiency of photogenerated electron-hole pairs. The optimized Ag 3 VO 4 /Ag 2 CO 3 composite can effectively degrade organic pollutants (rhodamine b (RhB), methylene blue (MB), levofloxacin (LVF), and tetracycline). More specifically, the Ag 3 VO 4 /Ag 2 CO 3 photocatalyst with a 1:2 mass ratio (VC-12) can remove 97.8% and 82% of RhB and LVF within 30 and 60 min, respectively. The LVF degradation rate by VC-12 under visible light irradiation is more than 12.8 and 21.51 times higher than those of pure Ag 3 VO 4 and Ag 2 CO 3 , respectively. The excellent photocatalytic activity of the Ag 3 VO 4 /Ag 2 CO 3 hybrid system is mainly attributed to the internal electric field that forms in the Ag 3 VO 4 /Ag 2 CO 3 p–n heterojunction system, the photogenerated electron hole pairs that separate and facilely migrate, and the specific surface area of VC-12 that is larger than that of the monomer. In addition, the degradation efficiency of VC-12 did not decline significantly after four cycles. In this study, the photocatalytic mechanism for Ag 3 VO 4 /Ag 2 CO 3 photocatalysts is explored in detail based on the energy band analysis results, trapping experiment results, and electron spin resonance spectra. Finally, the LVF degradation products are analyzed by liquid chromatography–mass spectrometry, and the potential LVF degradation pathway is identified. The experiments performed in this research therefore lead to new motivation for the design and synthesis of highly efficient and widely applicable photocatalysts for environmental purification. • Ag 3 VO 4 /Ag 2 CO 3 p-n heterojunction was prepared by a one-step co-precipitation method. • Photocatalytic activity and stability of VC-12 was significantly enhanced. • The detailed LVF photocatalytic degradation intermediate pathway is proposed. • The internal electric field of the composite facilitates the separation of carriers.