Ionic liquid-assisted solvothermal synthesis of three-dimensional hierarchical copper sulfide microflowers at a low temperature with enhanced photocatalytic performance

Abstract

Three-dimensional (3D) hierarchical copper sulfide (CuS) microflowers have been successfully constructed by a facile ionic liquid (1-butyl-3-methylimidazolium chloride, [BMIm]Cl)-assisted solvothermal method at a low temperature (65 °C). Covellite CuS assembled into nanoflakes with a thickness of 8–10 nm and a lateral dimension of about 700 nm was obtained by the decomposition of intermediate complex Cu₃(TAA)₃Cl₃ (thioacetamide, TAA) blocks. The ionic liquid (IL) could serve as a solvent, ligand, and structure-directing agent, which played an important role in the morphologies of Cu₃(TAA)₃Cl₃ and CuS. It is found that CuCl could be interacted with [BMIm]Cl, leading to the formation of [BMIm]CuCl₂. Furthermore, the CuS crystal growth along the <001> direction was inhibited by the absorption of alkylimidazolium rings ([BMIm]⁺) on the (001) facets of CuS. The morphology and size of CuS were controllable by changing the concentration of [BMIm]Cl. Moreover, 3D hierarchical CuS microflowers used as the photocatalyst showed enhanced visible-light photocatalytic activity for the degradation of methylene blue (MB), due to their large specific surface area, mesoporous structure, and advantageous optical properties. This synthetic method could be expanded to prepare other metal chalcogenides, owing to its simple and safe operation, mild reaction conditions, and low cost.