Efficient visible light-driven core–shell-structured ZnS@Ag 2 S nanoparticles-anchored reduced graphene oxide for the reduction of Cr( vi )

A ZnS@Ag 2 S/RGO nanocomposite with high catalytic efficiency was synthesized via hydrothermal method using l -cysteine as the sulfur source. The morphology, crystal structure, and surface chemistry of ZnS@Ag 2 S/RGO was characterized by UV-Vis, X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), Raman, and photoluminescence (PL). The TEM image shows core–shell ZnS@Ag 2 S nanoparticles uniformly distributed on RGO sheets. The photocatalytic activity of ZnS@Ag 2 S/RGO was evaluated by the reduction of Cr( vi ) under visible light irradiation. ZnS@Ag 2 S/RGO showed higher activity in Cr( vi ) reduction compared to ZnS@Ag 2 S and ZnS under similar conditions. The superior photocatalytic activity of ZnS@Ag 2 S/RGO was ascribed to the more efficient separation/transfer of charge carriers as well as the enhanced visible light harvesting. The effect of the amount of catalyst, pH, and Cr( vi ) concentration on the reduction efficiency of the nanocomposite was investigated. This study showed that the complete reduction of Cr( vi ) in the presence of ZnS@Ag 2 S/RGO occurs within a short exposure time of as low as 40 min at optimized conditions.