Twins in polyhedral 26-facet Cu7S4 cages: Synthesis, characterization and their enhancing photochemical activities

Unusual polyhedral 26-facet Cu7S4 cages wholly exposed with amazingly unique nanotwinned structures as building blocks were successfully synthesized via a facile ethanol-assisted sacrificial Cu2O templates approach. Furthermore, a solvent-controlled fabrication of polyhedral copper sulfides (Cu7S4 and CuS) with different stoichiometries and microstructures can be artificially achieved, which is determined by the intrinsic difference of the surface states of Cu2O templates. Structural and morphological evolutions were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and field-emission scanning electron microscopy (FESEM). Stoichiometric-dependent characteristics were demonstrated in the UV-vis absorption investigations. The as-prepared Cu7S4 microcages exhibit higher photocatalytic activity for enhancing degradation of methylene blue, which might be attributed to their special nanotwinned building blocks. This study is of great importance in bottom-up assembly of unusual ordering hollow copper sulfides superstructures, but also offers a good opportunity to understand the fundamental significance of nanotwinned structures for their potential applications.