CuS–Bi2S3 hierarchical architectures: controlled synthesis and enhanced visible-light photocatalytic performance for dye degradation

Abstract

Novel CuS–Bi₂S₃ heterojunctions were fabricated by a one-step solvothermal method using glycol as solvent and L-lysine as structure-directing reagent. By varying the sulfur sources, CuS–Bi₂S₃ composites of different morphologies were obtained. Novel microspheres composed of ultrathin nanosheets and radial nanoneedles were synthesized using potassium thiocyanate (PT) and thiourea (TU) as sulfur sources, respectively. Based on the experimental and characterization results, we proposed a step-by-step mechanism for the growth of the CuS–Bi₂S₃ hierarchical architectures based on the different release rates of S²⁻ in the preparation process. It was observed that the CuS–Bi₂S₃ nanocomposites show high photocatalytic activity for the degradation of dyes (Rh-B and CV, as well as both of them in an aqueous solution) under visible light (λ ≥ 400 nm), showing performance much higher than those reported in the literature. In terms of sulfur precursors, the degradation rates can be arranged in the following order: TU > PT > ST > SS, and the optimal conditions for composite preparation are a crystallization time of 6 h and a Bi/Cu molar ratio of 10 : 1. The good photocatalytic activity is attributed to the matching of the CuS and Bi₂S₃ band-gap energies as well as the CuS/Bi₂S₃ interfaces that facilitate transfer and separation of photogenerated charge carriers. With high stability, the CuS–Bi₂S₃ composites have high potential for the photodegradation of dyes in water-treatment processes.