The construction of Z-scheme heterojunction ZnIn2S4@CuO with enhanced charge transfer capability and its mechanism study for the visible light degradation of tetracycline.

In this study, Z-type ZnIn 2 S 4 @CuO composites with a core–shell structure were synthesized. Under visible light irradiation, ZnIn 2 S 4 @CuO generates electron-hole pairs, and the presence of an internal electric field (IEF) improves the charge transfer mechanism of the composites and promotes the separation of charge carriers. The electrons on the conduction band of ZnIn 2 S 4 combine with dissolved oxygen in water to generate •O 2 –, and the holes on the valence band of CuO combine with OH– and H 2 O in water to generate •OH, and the generated reactive substances attack atoms on the TC to cause its ring-opening degradation, and ultimately mineralize the TC into CO 2 and H 2 O. [Display omitted] • A novel method for efficient construction of binary composites is proposed. • Z-type heterostructure reduces the photogenerated carrier complexation efficiency. • Verification of the Z-structure charge transfer mechanism. • TC degradation pathways proposed in combination with HR-MC and FEDs. In this study, copper oxide (CuO) was prepared by the microwave-assisted hydrothermal technique subsequently, CuO was grown in situ onto different rare metal compounds to prepare Z-scheme heterojunctions to improve the degradation efficiency of tetracycline (TC) in water environments. Various characterization proved the successful synthesis of all composite materials, and the formation of tight heterojunction interfaces, among which, the core–shell structure ZnIn 2 S 4 @CuO exhibited excellent photocatalytic degradation capability. Research results indicated that the degradation efficiency of ZnIn 2 S 4 @CuO for TC (50 mg/L) in the water environment reached 95.8 %, and the degradation rate is 2.41 times and 12.93 times that of CuO and ZnIn 2 S 4 alone, respectively, the reason is because of the introduction of ZnIn 2 S 4 , Z-scheme heterojunction structures and internal electric field (IEF) is constructed and formed to extend the visible light response range of photocatalysts to improve electron-hole separation efficiency, and enhance charge transfer. In addition, ZnIn 2 S 4 @CuO-2 exhibited good stability and reproducibility, with no significant loss of activity after five cycles. Finally, the precise locations of free radical attack on TC were investigated by the combined use of high-resolution mass spectrometry (HR-MC) and frontier electron densities (FEDs), and a reasonable degradation pathway was provided. The results of this research provide a new and viable approach to overcome the limitations of conventional photocatalytic materials in terms of limited visible light absorption range and fast carrier recombination rates, which offers promising prospects for a wide range of applications in the field of wastewater purification. [ABSTRACT FROM AUTHOR]