Gram-scale wet chemical synthesis of wurtzite-8H nanoporous ZnS spheres with high photocatalytic activity

Abstract

Wurtzite-8H nanoporous ZnS spheres assembled from crystallites, were synthesized via a “green” wet chemical route. A possible formation mechanism for the growth process of the ZnS spheres has been proposed based on experimental observations. The prepared catalysts are characterized by transmission electron microscopy, high-resolution transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, N2 adsorption–desorption isotherms, elemental analysis, and UV–vis absorption spectroscopy. The catalyst showed high and stable photocatalytic activity for the degradation of persistent toxic organic pollutants, as demonstrated with azo dye X-3B (X-3B), trichloroacetate (TCA) and phenol under both visible (>420nm) and UV light irradiation. The experimental results demonstrate that the photocatalytic activity of ZnS spheres is 3.3 and 9 times higher than that of Degussa P25 and commercial ZnS, respectively. The production of OH radicals on the ZnS surface was detected by the photoluminescence (PL) technique using coumarin as a probe molecule, which suggests that OH radicals are the dominant photo-oxidant in the photocatalytic reaction. More importantly, this synthesis method can be economical for a scale-up process, and may also be applicable to the preparation of additional II–VI semiconductors for catalysis and other applications.