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Nickel-cobalt layered double hydroxide ultrathin nanosheets coated on reduced graphene oxide nonosheets/nickel foam for high performance asymmetric supercapacitors

Shahrokhian, S ; Sharif University of Technology | 2018

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  1. Type of Document: Article
  2. DOI: 10.1016/j.ijhydene.2017.12.019
  3. Publisher: Elsevier Ltd , 2018
  4. Abstract:
  5. Here in, for the first time, we report a new and simple procedure for preparing reduced graphene oxide/nickel-cobalt double layered hydroxide composite on the nickel foam (Ni-Co LDH/rGO/NF) via a fast and simple two-step electrochemical method including potentiostatic routes in the presence of CTAB as a cationic surfactant. Graphene oxide coated nickel foam prepared by simple immersion method. After that, the prepared electrode reduced electrochemically to obtain rGO/NF electrode. Finally, the rGO/NF electrode was used as cathode for electrodeposition of Ni-Co LDH in the presence of CTAB as cationic surfactant. The prepared electrodes were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), Energy-dispersive X-ray spectroscopy (EDS), Brunauer, Emmett and Teller (BET) and electrochemical techniques such as voltammetry (CV), galvanostatic charge-discharge curves (GCD) and electrochemical impedance spectroscopy (EIS). The resulting electrode which prepared in the presence of CTAB afforded extremely high specific capacitance of 2133.3 F g−1 at a current density of 4 A g−1. FE-SEM, TEM and EDS mapping results showed that Ni-Co LDH nanosheets uniformly covered the surface of rGO/NF in the presence of CTAB, and is closely packed and thinner in thickness compared with the sample prepared in similar way without using surfactant. Such new thin and dense morphology facilitates electrolyte ions diffusion through the prepared electrode. A good cycling stability was obtained for the electrode in alkaline media. EIS measurements showed low values of internal resistance (Rs) and charge transfer resistance (Rct), indicating that the prepared nanocomposite is a promising candidate for supercapacitor applications. The asymmetric supercapacitor (ASC) based on the Ni-Co LDH/CTAB/rGO/NF as a positive electrode and rGO/NF as a negative electrode was assembled and it exhibited a Cs of 71.4 F g−1 at a current density of 2 A/g and correspondingly energy density of as high as 68 Wh kg−1. © 2017 Hydrogen Energy Publications LLC
  6. Keywords:
  7. Nickel/cobalt layered double hydroxide ; Reduced graphene oxide ; Surfactant ; Cationic surfactants ; Charge transfer ; Cobalt alloys ; Cobalt compounds ; Dyes ; Electric discharges ; Electrochemical impedance spectroscopy ; Electrodeposition ; Electrolytes ; Enamels ; Energy dispersive spectroscopy ; Field emission cathodes ; Field emission microscopes ; Foams ; Fourier transform infrared spectroscopy ; Graphene ; High resolution transmission electron microscopy ; Nanosheets ; Nickel compounds ; Scanning electron microscopy ; Supercapacitor ; Surface active agents ; Transmission electron microscopy ; X ray diffraction ; Charge transfer resistance ; Energy dispersive X ray spectroscopy ; Field emission scanning electron microscopy ; Galvanostatic charge discharges ; Layered double hydroxides ; Reduced graphene oxides ; Supercapacitor application ; Two step electrochemical method ; Electrochemical electrodes
  8. Source: International Journal of Hydrogen Energy ; Volume 43, Issue 4 , 2018 , Pages 2256-2267 ; 03603199 (ISSN)
  9. URL: https://www.sciencedirect.com/science/article/abs/pii/S0360319917346554