Abstract
Nitrogen-doped graphene (NDG) and mixed metal oxides have been attracting much attention as the combination of these materials resulted in enhanced electrochemical properties. In this study, a composite of nitrogen-doped graphene/manganese oxide/iron oxide (NDG/Mn3O4/Fe3O4) for a supercapacitor was prepared through the hydrothermal method, followed by freeze-drying. Field emission scanning electron microscopy (FESEM) images revealed that the NDG/Mn3O4/Fe3O4 composite displayed wrinkled-like sheets morphology with Mn3O4 and Fe3O4 particles attached on the surface of NDG. The presence of NDG, Mn3O4, and Fe3O4 was characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The electrochemical studies revealed that the NDG/Mn3O4/Fe3O4 composite exhibited the highest specific capacitance (158.46 F/g) compared to NDG/Fe3O4 (130.41 F/g), NDG/Mn3O4 (147.55 F/g), and NDG (74.35 F/g) in 1 M Na2SO4 at a scan rate of 50 mV/s due to the synergistic effect between bimetallic oxides, which provide richer redox reaction and high conductivity. The galvanostatic charge discharge (GCD) result demonstrated that, at a current density of 0.5 A/g, the discharging time of NDG/Mn3O4/Fe3O4 is the longest compared to NDG/Mn3O4 and NDG/Fe3O4, indicating that it had the largest charge storage capacity. NDG/Mn3O4/Fe3O4 also exhibited the smallest resistance of charge transfer (Rct) value (1.35 Ω), showing its excellent charge transfer behavior at the interface region and good cyclic stability by manifesting a capacity retention of 100.4%, even after 5000 cycles.
Highlights
The rapid growth of the human population and the development of the global economy has caused the increasing demand for energy
Supercapacitors are always preferred due to their high performance in energy storage compared to batteries, flywheels, and traditional capacitors
Manganese sulphate monohydrate (MnSO4 ·H2 O), polytetrafluoroethylene (PTFE), and carbon mesoporous were obtained from Sigma-Aldrich (Steinheim, Germany)
Summary
The rapid growth of the human population and the development of the global economy has caused the increasing demand for energy. The global energy need is predicted to be doubled by the mid-century and more than triple by the end of this century [1]. An energy storage system is needed to store excess energy generated and to supply it to electrical devices effectively. Supercapacitors are always preferred due to their high performance in energy storage compared to batteries, flywheels, and traditional capacitors. This is because batteries have high energy density, but low power density and short life cycles. Traditional capacitors can be charged and discharged in a short time, but they have low energy density
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