Physical and Electrochemical Properties of Graphene Decorated with ZnO Hollow Spheres for Supercapacitor Applications

Single-layer graphene-ZnO hollow sphere (SLG-ZnO(HS)) composites were successfully prepared through facile one-step solvothermal synthesis route. The morphological structures of the samples were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Hollow spheres consisting of ZnO nanoparticles with a diameter of approximately 30 nm are decorated to both sides of the SLG sheets. The electrochemical performances were tested by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance (EIS). The SLG-ZnO(HS) composite electrode synthesized at a concentration of 0.25 mM Zn precursor exhibited an enhanced specific capacitance of 34.7 F/g at a scan rate of 1 mV/s with energy and power densities of 5.39 W h/kg and 1.73 kW/kg, respectively.

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