Synthesis and characterization of BiOCl–Cu₂ZnSnS₄ heterostructure with enhanced photocatalytic activity

Cu₂ZnSnS₄ QDs (5–7 nm) were synthesized by chemical coprecipitation route. Using prepared Cu₂ZnSnS₄ QDs, a new type of BiOCl–Cu₂ZnSnS₄ heterostructures were prepared using bismuth nitrate as a precurssor and potassium chloride as a source of chlorine at 100 °C, 4 h. BiOCl–Cu₂ZnSnS₄ heterostructures were analyzed by XRD, TEM, UV–visible NIR, PL and surface area studies. The diffracted peaks of BiOCl–Cu₂ZnSnS₄ heterostructure show the presence of tetragonal BiOCl and did not show the intense peaks of Cu₂ZnSnS₄ QDs. TEM images of BiOCl–Cu₂ZnSnS₄ showed the deposition of Cu₂ZnSnS₄ QDs on the BiOCl microsphere surface. The surface area of BiOCl, Cu₂ZnSnS₄ and BiOCl–Cu₂ZnSnS₄-1 was of 1.91 m²/g, 3.06 m²/g and 13.39 m²/g, respectively. BiOCl–Cu₂ZnSnS₄-1 had a higher photodegradation rate for Congo red dye than BiOCl and Cu₂ZnSnS₄ QDs under sunlight, and that higher photoactivity was due to the heterostructure effect between BiOCl and Cu₂ZnSnS₄ QDs along with increased optical absorption in the visible region. Scavenger study endorses the involvement of superoxide and holes radicals in the degradation of Congo red.