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.