Hydrothermal deposition of manganese dioxide nanosheets on electrodeposited graphene covered nickel foam as a high-performance electrode for supercapacitors

In this paper, the graphene oxide nanosheets are simultaneously reduced and deposited on nickel foam (denoted as Ni-foam@GNS) by one step electrodeposition method. The interconnected crumpled graphene nanosheets grown on Ni foam serve as a three-dimensional (3D) conductive skeleton for hydrothermal deposition of MnO2 nanosheets by in-situ redox reaction. The MnO2 nanosheets anchored on the graphene covered nickel foam (denoted as Ni-foam@GNS@MnO2) show unique 3D porous interconnected networks. The samples are characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), N2 adsorption-desorption measurements and fourier transform infrared spectroscopy (FT-IR). The capacitive performances are researched by cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS). The results reveal that the Ni-foam@GNS@MnO2 electrode exhibits a high specific capacitance of 462 F g−1 at 0.5 A g−1 and excellent capacitance retention of 93.1% after 5000 cycles at 10 A g−1. Furthermore, the Ni-foam@GNS@MnO2 electrode delivers a high energy density of 26.1 Wh kg−1 even at a high power density of 3981 W kg−1. These results demonstrate that the Ni-foam@GNS@MnO2 composite offers great promise in large-scale energy storage device applications.