Study on Photochemical Properties of a Sr-SnS2/CaIn2S4 Heterostructure to Improve Cr(VI) Removal

Compound semiconductor photocatalysis technology is considered to be a promising treatment for solving water problems efficiently. The point of designing high-efficiency catalysts is to optimize the band gap structure and facilitate the separation of charge carriers by establishing new electron migration pathways. Recently, 3D porous CaIn2S4 was found to have good photocatalytic ability. However, the quick recombination and agglomeration of carriers still limit its application. Herein, we prepared a heterostructure by introducing 2D Sr-doped SnS2 to 3D CaIn2S4 by a hydrothermal synthesis method. The optimal dosage of Sr-SnS2 is 3%, and the photocatalytic Cr(VI) removal efficiency of 3% Sr-SnS2/CaIn2S4 (SSCS-3) is 5.82 and 10.83 times those of pure CaIn2S4 and SnS2, respectively. According to the results of characterization tests and calculation verification, we inferred that the enhanced photocatalytic removal of Cr(VI) is due to the introduction of Sr-SnS2 that can promote the rapid transfer of photogenerated electrons to the surface of CaIn2S4, and the heterostructure formed between 2D Sr-SnS2 and 3D CaIn2S4 can also provide abundant reaction sites. The promotion of carrier separation is mainly due to the formation of a built-in electric field of the Sr-SnS2/CaIn2S4 heterostructure. This work provides new ideas and technologies for the treatment of Cr(VI) in wastewater.