The role of the Se-rich and Se-poor conditions in the photocatalytic performance of ZnSe/rGO nanocomposites

Abstract

PristineSe-rich ZnSe, Se-rich ZnSe/graphene-oxide (GO), pristine Se-poor, and Se-poor ZnSe/GO nanocomposites were synthesized as the visible-light photocatalytic materials. The electron microscope images of the samples showed a micropolyhedron morphology for the pristine Se-rich ZnSe, which this morphology was changed to the nanoparticle (NP) in the ZnSe/GO. On the other hand, the pristine Se-poor ZnSe presented a nanobelt (NB) morphology, which this morphology was converted to a mixed morphology of NBs and NPs by GO. The visible-light photocatalytic activity of the products to degrade methylene blue (MB) dye showed that the GO had a synergetic effect for the photocatalytic performance in both types of samples. However, the Se-rich ZnSe/GO nanocomposites presented an enhancement photocatalytic performance. X-ray diffraction (XRD) and Raman results indicated the GO sheets were converted into reduced GO (rGO) during the synthesis process. Although, Raman and X-ray photoelectron spectroscopy (XPS) results indicated a higher reduction level for the GO sheets in the S-rich ZnSe/rGO nanocomposites. This higher reduction level of GO sheets in the Se-rich ZnSe/rGO nanocomposites led to decreasing the electrical resistance of these nanocomposites in comparison to the Se-poor ZnSe/rGO nanocomposites. This higher conductivity of the Se-rich ZnSe/rGO nanocomposites was the most important factor to enhance the photocatalytic performance.