Supercapacitive performance of N-doped graphene/Mn 3 O 4 /Fe 3 O 4 as an electrode material

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/Mn 3 O 4 /Fe 3 O 4 ) for a supercapacitor was prepared through the hydrothermal method, followed by freeze-drying. Field emission scanning electron microscopy (FESEM) images revealed that the NDG/Mn 3 O 4 /Fe 3 O 4 composite displayed wrinkled-like sheets morphology with Mn 3 O 4 and Fe 3 O 4 particles attached on the surface of NDG. The presence of NDG, Mn 3 O 4 , and Fe 3 O 4 was characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The electrochemical studies revealed that the NDG/Mn 3 O 4 /Fe 3 O 4 composite exhibited the highest specific capacitance (158.46 F/g) compared to NDG/Fe 3 O 4 (130.41 F/g), NDG/Mn 3 O 4 (147.55 F/g), and NDG (74.35 F/g) in 1 M Na 2 SO 4 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/Mn 3 O 4 /Fe 3 O 4 is the longest compared to NDG/Mn 3 O 4 and NDG/Fe 3 O 4 , indicating that it had the largest charge storage capacity. NDG/Mn 3 O 4 /Fe 3 O 4 also exhibited the smallest resistance of charge transfer (R ct ) 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.