In situ decoration of SnS quantum dots on the α-SnWO4 nanosheets for superior visible-light photocatalytic performance

Abstract

A novel heterostructure consisting of SnS quantum dots (QDs) and α-SnWO4 nanosheets was constructed through the crystallization of amorphous precursor using a one-pot hydrothermal method. The formation of SnS/α-SnWO4 heterostructure was confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) techniques: the SnS QDs with the average particle size of 2.2 nm were uniformly anchored on the surface of α-SnWO4 nanosheets. The amorphous α-SnWO4 precursor with negative charge can attract the excessive Sn2+ ions and further react with S2- to form SnS/α-SnWO4 heterojunction. The intimate contact between SnS QDs and α-SnWO4 nanosheets was beneficial to the effective separation of photo-created electron-hole pairs. Thus, the SnS/α-SnWO4 nanocomposites exhibited the enhanced photocatalytic activity in the degradation of methyl orange (MO), Rhodamine B (RhB) and tetracycline (TC). The optimal amount of SnS QDs on the α-SnWO4 surface was 2 mol%, whose photodegradation efficiency was about 95.56% for MO removal after 90 min visible-light illumination and its degradation rate (0.0338 min−1) was 8.7 times higher than that of pure α-SnWO4 (0.0039 min−1). The trapping experiments evidenced that the ·O2–, h+ and ·OH play important roles in the photocatalysis process. The superior photocatalytic performance of SnS/α-SnWO4 nanocomposite would be ascribed to the Z-scheme photocatalytic reaction mechanism.