Synthesis Of MnO₂/polyaniline Nanorod Arrays Based On Graphene And Its Electrochemical Performance

In recent years, Supercapacitors have attracted more and more interests of researchers due to its high power density, fast charging-discharging rate and excellent long cycle life. The electrochemical performance of supercapacitors is highly dependent on the performance of electrode materials. Carbon-based active materials, metal oxide and conducting polymer are used as main materials in electrode of supercapacitors. Among numerous conductive polymers, polyaniline(PANI) is considerably attractive. However, the PANI-based electrodes always suffer from poor cycle stability, so the binary and ternary composites of PANI with graphene and manganese dioxide(Mn O2), which are also regarded as the promising electrode materials, have aroused the attention of the researchers. However, until now, studies about graphene/Mn O2/PANI ternary composite are still limited, and in the only researches, the components were combined together in a randomly disordered structure. And thus, the utilization of each component was limited. In order to further improve the stability of PANI-based and enhance the electrochemical performance of graphene/Mn O2/PANI ternary composite, graphene/Mn O2/PANI nanorod arrays(GMPNAs) were fabricated firstly.In this research, Graphite oxide was synthesized by the Hummers’ method. Then, graphene was got through reducing graphite oxide with hydrazine. The ternary composite of graphene/Mn O2/PANI nanorod arrays was fabricated successfully via casting the graphene onto the surface of glassy carbon piece, followed by the deposition of Mn O2 nanorod arrays on graphene film and synthesis of PANI on the surface of Mn O2 nanorod arrays with cyclic voltammetry(CV) electrodeposition. The microstructure and morphology of the samples were characterized by Fourier transform infrared spectra(FTIR), Raman spectra, X-ray diffraction(XRD), scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The electrochemical performance of the all fabricated materials was determined by CV, galvanostatic charge/discharge and electrochemical impedance spectroscopy(EIS) measurements. The results of experiment as follows:Graphene can form a uniform film when casting with the concentration of 0.2 mg ml-1, and the uniform film is conducive to the form of more ordered Mn O2 nanorods, which have more excellent electrochemical performance. The specific capacitance of graphene achieves 95 F g-1 at a current density of 10 A g-1, and it also demonstrates excellent reversibility and stability.By comparing the morphologies of Mn O2 when the graphene film, as support material, is present or absent, it can be found that ordered Mn O2 nanorod are distributed on the surface of graphene, and Mn O2 nanoflakes are obtained while directly deposited on glassy carbon piece without graphene film, which indicate that graphene, used as support material for the deposition of Mn O2, plays a decisive role in the formation of nanorod. Studie have shown that graphene change the nucleation and crystal growth mode of Mn O2 from isotropic to anisotropic, leading to the difference of Mn O2 morphology.Specific capacitance and cycling stability tests of GMPNAs show the maximum specific capacitance of GMPNAs is as high as 755 F g-1 at a current density of 0.5 A g-1 and the capacitance retention is 87% after 1000 cycles at 10 A g-1. Thus, it is believed that the GMPNAs composite as-prepared will have a great potential for application in supercapacitors.