Highly enhanced photocatalytic performance of Zn(1−x)MgxO/rGO nanostars under sunlight irradiation synthesized by one-pot refluxing method

Abstract

The current research presents a simple, coast-effective, and one-pot refluxing method to synthesize Zn(1−x)MgxO nanostructures, which were decorated on graphene oxide (GO) sheets. In the first step, the effect of refluxing time on structure and morphology of the pristine ZnO nanostructures was investigated. X-ray diffraction (XRD) patterns indicated that the pristine ZnO nanostructures were formed after 8 h of the refluxing process. Field emission electron microscope (FESEM) images showed that stars-shape ZnO nanostructures were formed after 10 h of refluxing time. Further refluxing process for 12 h showed that morphology and structure of the ZnO nanostructures were not changed. However, after 14 h additional phases were formed. Therefore, ZnO and Zn(1−x)MgxO nanostars that were decorated on GO sheets were synthesized during 10 h. XRD patterns indicated that GO sheets were changed into reduced graphene oxides (rGO) during the refluxing process. Transmission electron microscope (TEM) images revealed that ZnO nanostars with more branches were decorated on rGO sheets. However, the TEM images showed that the morphology of ZnxMg(1−x)O/rGO nanocomposites were changed significantly with the increase of Mg concentration up to 6%. Photocatalytic performance of the products was examined under natural sunlight irradiation. The results showed that the rGO and Mg concentrations had significant roles in the photocatalytic performance of ZnO nanostars. The concentrations of Mg and rGO increased up to 4% were the optimum concentration for enhancing photocatalytic performance of Zn(1−x)MgxO/rGO nanocomposites. In addition, room temperature photoluminescence (PL) spectroscopy and photocurrent measurement results indicated that Mg and rGO with optimum concentration caused decrease of electron-hole recombination rate.