Photocatalytic performance of graphene-based Cr-substituted β ZnS nanocomposites

Nitrogen-doped 2D graphene nanosheets were wrapped on the sphalerite structured pure and Cr substituted ZnS nanospheres synthesized by hydrothermal method successfully and examined as novel photocatalysts to the photodegradation of dye mixtures as realistic pollutants. 2D graphene nanosheets were successfully synthesized by Hummer's method using natural coal. XRD, Raman spectroscopy, and XPS were correlated to each other, and vacancy defects were found to increase in graphene/4% Cr:ZnS nanocomposites due to the existence of stacking faults, microstrain, dislocation density, grain boundaries, point defects, doping, and graphitic edges. The drastic change was noticed in C 1 s spectra of graphene and graphene/pure ZnS, graphene/4% Cr:ZnS nanocomposites owing to the stress, strain property of graphene, and development of vacancy defects. N-doped 2D graphene nanosheets were decorated on the surface of ZnS nanospheres which was confirmed by FESEM. The addition of 2D graphene nanosheets results in the enhancement of dislocation density, microstrain, and stacking faults in the samples. From XRD, the dislocation density, microstrain, and stacking faults were decreased due to the doping of Cr into the ZnS lattice. From XPS, it was verified that the highest vacancy defects were scrutinized in graphene/4% Cr:ZnS nanocomposite due to the ionic radius of Cr there were more vacancies were created into ZnS lattice. The dyes of methylene blue, para nitrophenol and, Congo red were mixed into 100 ml of water under solar light for degradation. The photocatalytic efficiencies were found to be 57.36, 62.79, 59.68, 84.49, and 51.16% for pure ZnS, 4% Cr:ZnS, graphene/pure ZnS, graphene/4% Cr:ZnS, and graphene, respectively. Morphological, chemical, and optical properties of graphene nanosheets based on Cr substituted ZnS nanocomposites were studied before and after the photocatalytic activity.