Template-free synthesis of complicated double-wall Cu2O hollow spheres with enhanced visible photocatalytic activities

Abstract

In this study, complicated double-wall Cu₂O hollow spheres have been successfully prepared by a facile hydrothermal process in a ternary solvent system including water, ethanol and glycerol. The obtained double-wall Cu₂O hollow spheres have an average diameter of ∼15 μm and the spheres are assembled by irregular particles with an average diameter of ∼500 nm. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the structure of the synthesized products. The formation mechanism of the double-wall Cu₂O hollow spheres is related to a self-assembly process accompanied by an Ostwald ripening process, during which the Cu₂O spheres are first formed through the self-assembly of Cu₂O nanoparticles and then gradually develop into double-wall hollow interiors by an Ostwald ripening process. Furthermore, the photocatalytic properties of the as-obtained samples were investigated. It is found that such unique double-wall hollow architecture exhibits excellent photocatalytic efficiency for the degradation of MO under visible-light illumination, which is up to 90.3% and this photocatalytic efficiency is higher than the Cu₂O particles with irregular spherical structure (74.2%). The high photocatalytic performance of the double-wall Cu₂O hollow spheres is associated with the fact that there are plenty of nanopores which exist in the spheres, serving as transport paths for small molecules.