Layered double hydroxides (LDHs) of transition metals
have attained
significant attention for supercapacitor applications due to their
excellent charge storage, low internal resistance, and superior electrochemical
stability. Here, a nanocomposite of reduced graphene oxide/nickel
cobalt layered double hydroxide (rGO/NiCo LDH) on the surface of nickel
foam (NF) containing hierarchical nickel cobalt copper transition
metal oxides (TMOs) is prepared through two-step processes of electrochemical
and coprecipitation methods. The TMOs/rGO/NiCo LDH nanocomposite is
characterized by X-ray diffraction (XRD), Fourier transform infrared
(FTIR), Raman, X-ray energy-dispersive (EDS), and X-ray photoelectron
(XPS) spectroscopies as well as by transmission electron microscopy
(TEM), field-emission scanning electron microscopy (FE-SEM), elemental
mapping analysis, nitrogen adsorption/desorption, and contact angle
measurements. The supercapacitive behavior of the electrodes has been
investigated through cyclic voltammetry (CV), galvanostatic charge–discharge
(GCD) measurements, and electrochemical impedance spectroscopy (EIS).
The study has shown that the synergetic effect and the electrochemical
properties have considerably improved when the layered double hydroxides
are synthesized in the presence of rGO. The TMOs/rGO/NiCo LDH nanocomposite
exhibits an excellent specific capacitance of 2763 F g–1 at a current density of 1 A g–1 and a stability
of 85% after 3000 GCD cycles at a current density of 24 A g–1. Also, a TMOs/rGO/NiCo LDH//rGO asymmetric supercapacitor device
is constructed with an aqueous KOH electrolyte, which shows a capacitance
of 244 F g–1 at a current density of 1 A g–1. The device attains the highest energy density of 34 Wh kg–1 and power density of 2500 W kg–1, with an excellent
cycling stability of 100% after 3000 GCD cycles at a current density
of 10 A g–1.