Graphene-ZnO hallow microspheres composite for supercapacitor applications

Through a facile solvothermal synthesis process, a graphene-Zno microspheres composite was produced at 180°C for 24 hours. Raman spectroscopy, X-Ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were used to analyse the morphological structures of the materials. The analysis revealed that homogeneous microspheres assembled by hexagonal phase wurtzite ZnO nanoparticles were decorated on the graphene sheets via graphene oxide (GO) functional groups. The ZnO nanoparticles are about 30 nm in size and the microspheres are hollow. A possible growth mechanism for the formation of ZnO hollow microspheres anchored on graphene sheets has been proposed. Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance (EIS) were used to evaluate the electrochemical performance of the composite. At a scan rate of.1mV/s, the graphene-ZnO hollow microspheres (rGS-ZnO(HMs)) composite electrode demonstrated enhanced specific capacitance of 40.70 F/g with respective energy and power densities of 5.75 W h/kg and 1.97 kW/kg.