A 3D/2D β-In ₂ S ₃ /SnS ₂ /SnS Heterojunction with Excellent Photocatalytic Degradation of Tetracycline

Photocatalysis is one of the effective solutions to solve the problem of antibiotic pollution in water resources. In this work, In₂S₃/SnS₂/SnS heterojunction photocatalysts are designed and synthesized by a simple two-step hydrothermal method to treat a tetracycline (TC) antibiotic under visible light. The successful combination of 3D β-In₂S₃ nanoflowers with 2D SnS₂/SnS nanosheets is confirmed through SEM, TEM, XRD, Raman, and XPS results. Especially, the mole ratio of In and Sn is 1:1 among In₂S₃/SnS₂/SnS heterojunctions, which shows the highest photodegradation efficiency, reaching 95.2% for the degradation of TC (10 ppm) within 60 min under the irradiation of a low-power household LED lamp (80 W), which far exceeds the majority of the previously reported sulfide photocatalysts. Furthermore, the intermediate products of photocatalytic degradation are identified by HPLC-MS/MS to better understand the degradation pathways. In addition, O₂^•- radicals are the main active species in the photocatalytic reaction of the as-synthesized composites, as determined through the capture experiments. Based on the experimental results and theoretical analysis, a charge transfer mechanism according to the S-scheme is proposed. In₂S₃/SnS₂/SnS with excellent photocatalytic properties and high structural stability is a promising material for the practical degradation of antibiotic wastewater.