Theoretical and experimental study on the band gap of binary ZnS-CdS nanocomposites and expected best photocatalysts

Abstract

In this study, ZnS-CdS nanocomposites were synthesized using a hydrothermal method to investigate their photocatalytic activity. The X-ray diffraction (XRD) results confirmed the formation of hexagonal structure for cadmium sulfide and zinc sulfide nanocomposites and the results of the scanning electron spectroscopy (SEM) indicated that by adding ZnS to cadmium sulfide's structure the size of the nanoparticles decreases, which is a clear sign of improved photocatalytic activity. Using absorption coefficient and UV-visible spectroscopy (UV), the band gap of pure CdS was obtained as 2.7 eV, by adding the Zn content the gap will decrease. The photocatalytic activity of prepared nanocomposites was studied by photodegradation of Rhodamine B (RhB) organic dye, and the synthesized sample with 0.1 M of zinc solution shows a smaller gap and size. In the next step, cadmium sulfide nanoparticles with different percentages of zinc were simulated and their HOMO-LUMO gaps were calculated by Density Functional Theory (DFT). In comparison to the other well-known functionals, it was found that M05 shows a better agreement with experimental results. The computational results confirm that the sample with 10% zinc content is a good candidate for photocatalytic activity.