Fabrication Of Novel Composite Material Of Porous Carbon/Multi-layer Graphene For Supercapacitors

Now, porous carbon materials have been attracting considerable attention owing to many advantages of high surface area, physical and chemical stability, porosity, good electrical conductivity, and low cost, which are recognized as most promising candidates for supercapacitors. However, current preparations of porous carbon usually are complicated. In this paper, composite carbon materials composed of porous amorphous carbons and graphene are fabricated by chemical vapor deposition(CVD) on Ni foil and Ni foam. The composite carbon materials possess good electrical conductivity, high strength and high surface area so that they are suitable as electrode materials for electrochemical capacitors. Electrochemical capacitors assembled by the composite carbon materials exhibit high specific capacitance, ultrahigh rate capability, wide frequency range, and high power density. Detailed research contents are as follows:Firstly, composite carbon film composed of porous carbons film and multilayer graphene(MLG) were prepared by ambient pressure chemical vapor deposition(APCVD) with Ni foils as catalysts substrates and methane as carbon source. The microstructure of the composite carbon films on silicon wafers were characterized by using field-emission scanning electron microscope(FESEM), Raman spectra, X ray diffraction(XRD). The results showed that the carbons film is porous carbon film, and the diameter ranges from several to ten nanometers. The graphene is multilayer graphene. The carbon films(including porous carbon film and multilayer graphene) can be easily transferred to arbitrary substrates. In addition, the composite carbon film can be directly assembled into electrochemical capacitors. Electrochemical behaviors are studied by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The result showed that the composite carbon film exhibited high rate capability, wide frequency range, good stability, reversibility and high area specific capacitance.Secondly, three-dimensional foam-like carbon materials were synthesized by APCVD with Ni foams as catalysts substrates and methane as carbon source. The structure of three-dimensional foam-like carbon materials can be simply controlled by adjusting growth temperature. ? Three-dimensional foam-like pure porous carbons material can fabricated in low growth temperature range(<620?). However, the three-dimensional foam-like porous carbons material is easy to collapse because of weak strength.? In the medium growth temperature area(625~700?), three-dimensional foam-like composite carbon materials composed of porous carbons and MLG were gained. In composite carbon material, the porous carbons were covered by discontinuous MLG slices. ? In high growth temperature(>700?), three-dimensional foam-like hollow MLG were formed, and internal surface of hollow MLG was covered by a layer of amorphous carbon. This whole composite carbon materials copied and inherited the interconnected 3D scaffold structure of the Ni foam templates.Finally, electrochemical capacitors were assembled by using three-dimensional foam-like carbon materials as electrodes, and tested by electrochemical workstation. The results indicated all capacitors exhibit good electrochemical performance: ultrahigh rate capability, wide frequency range, good stability, reversibility and high area specific capacitance. Moreover, three-dimensional foam-like carbon materials in growth temperature of 700? exhibited the highest area specific capacitance(703mF/cm2 at scan rate of 20 m V/s). On the contrary, porous carbons obtained at low temperature exhibited lowest area specific capacitance(119mF/cm2 at scan rate of 20 m V/s). The main reason for this was because that the three-dimensional foam-like composite carbon materials had high specific surface area and conductivity, however, three-dimensional foam-like amorphous carbon materials had low high specific surface area and poor electrical conductivity.