Efficient photodegradation of methylene blue by CdS-based nanocomposites

Abstract

In this research, CdS-based nanocomposites including Ag₂S-CdS, MnS-CdS, and ZnS-CdS were synthesized using the low-cost hydrothermal method for photocatalytic applications. The structural, morphological, porosity, and optical properties of these nanocomposites were examined by X-ray diffraction (XRD), Dynamic light scattering (DLS), Field Emission Scanning Electron Microscope (FE-SEM), Transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) method, Mott–Schottky, and UV–Visible spectra. Results proved that nanocomposites prepared at the nanoscale are not so pros. Also, DLS results showed the agglomeration of the particles. The UV–visible results indicated that the band gap of CdS (2.51 eV) changes in the range of 2.15–3.22 eV by adding the transition metal and a suitable amount of impurity metal decreases the band gap of CdS-based nanocomposites. FE-SEM and TEM analyses illustrated that the product was synthesized without impurity at the nanoscale. Position of conduction (CB) and valence band (VB) edges measured by Mott–Schottky analysis, which includes the reduction potential O₂/^⋅O₂⁻ and oxidation potential of ·OH/OH⁻. All in all, ZnS-CdS was the most efficient examined nanocomposite, indicating the best degradation rate of methylene blue (MB) under sunlight due to a small band gap, and appropriate positions of CB and VB.