Synthesis of hollow CdS micro-/nanospheres by CoSP technique and their visible light photocatalytic activities

CdS hollow micro-/nanospheres with high yield, purity, and photocatalytic property have been successfully synthesized by a continuous spray pyrolysis (CoSP) technique. The experimental conditions mainly the temperature and the nature of solvent are found to influence the creation of hollow spheres. The synthesized products have been characterized by X-ray powder diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), UV–vis and photoluminescence spectra. The XRD analysis confirmed the hexagonal crystal structure of the CdS microspheres supported by the measured lattice spacing from HR-TEM. The effects of synthesis temperature and the electric field applied during the spray on the formation of hollow spheres and their visible light photocatalytic properties are reported. Photodegradation of methylene blue (MB) dye under visible light was used to evaluate the performance of these CoSP made CdS micro-/nanospheres. The MB photodegradation efficiency was maximum, ∼90% in 2 h, for CdS microspheres prepared at 500 °C. The importance of hollow morphology over solid morphology is also proven; the hollow sphere sample (CdS5) is about twice efficient than solid sphere sample (CdS7). The results show that the CoSP method is a simple and inexpensive technique for preparing highly photo-active CdS hollow spheres which can be extended to prepare other sulphide and oxide hollow spheres at a large scale. Typically 100 mg of the powder can be prepared from ∼100 ml of spray solution.