Enhanced photocatalytic activity of BiOCl/BiOBr/SnS2 heterojunction using a superfine SnS2 and double S-scheme

Photocatalysis is a green approach to solving energy and environmental problems, and researchers are still pursuing high-performance photocatalysts. Although BiOX (X = Cl or Br) has a suitable bandgap and good stability, its photoresponse is mostly concentrated in the UV region. Conversely, SnS2 has a wide photoresponse range but exhibits perceptible photocorrosion and poor stability. To exploit the advantages of both BiOX and SnS2, this study hydrothermally synthesized and introduced superfine SnS2 (∼30 nm in size) into a BiOCl/BiOBr binary system to fabricate BiOCl/BiOBr/SnS2 composites. Subsequently, the degradation performance of these composites in a Rhodamine B solution under visible light was investigated. Results show that the BiOCl/BiOBr/SnS2 heterojunctions were successfully prepared and the composites exhibited the best photocatalytic performance with 6% mass fraction of SnS2 (BiOCl-to-BiOBr mol ratio = 1:1). The formation of a double S-schedule heterojunction between BiOCl/BiOBr and SnS2 not only accelerated charge separation and transfer but also broadened the photoresponse range and reduced photoelectron–hole recombination under full-spectrum irradiation. Loading a small narrow-bandgap photocatalyst onto a large photocatalyst provides an effective way to construct heterojunctions with excellent photocatalytic performance. The ternary photocatalyst presents a favorable photocatalytic stability, and its photodegradation rate is 4.6, 4.5 and 220.5 times that of BiOCl, BiOBr and SnS2, respectively.