Efficient Cr(vi) photoreduction under natural solar irradiation using a novel step-scheme ZnS/SnIn(4)S(8) nanoheterostructured photocatalysts

Removal of heavy metal pollutants from water is a challenge to water security and the environment. Therefore, in this work, multinary chalcogenide based nanoheterostructures such as ZnS/SnIn(4)S(8) nanoheterostructure with different loading amounts were prepared. The prepared nanoheterostructures were utilized as photocatalysts for chromium (Cr(vi)) photoreduction. The prepared nanoheterostructures were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), UV-Vis spectroscopy, dynamic light scattering (DLS), and X-ray photoelectron spectroscopy (XPS) and BET measurements. The absorption spectra of the prepared nanoheterostructures revealed that they are widely absorbed in the visible range with bandgap values 2.4–3.5 eV. The photocatalytic activities of prepared nanoheterostructures were studied toward the photoreduction of heavy metal, chromium (Cr(vi)), under irradiation of natural solar light. The ZnS/SnIn(4)S(8) (with ZnS molar ratio 20%) nanoheterostructures results showed a high photocatalytic activity (92.3%) after 120 min which could be attributed to its enhanced charge carrier separation with respect to the bare ZnS and SnIn(4)S(8) NPs. Also, the optoelectronic, valence-band XPS and electrochemical properties of the investigated photocatalysts were studied and the results revealed that the photocatalysts behave the step-scheme mechanism. The recyclability tests revealed a beneficial role of the surface charge in efficient regeneration of the photocatalysts for repeated use.