Electrochemical Preparation Of Graphene Composites And Its Energy Storage Properties

There are many methods for preparing graphene, such as mechanical cleavage,epitaxial growth, chemical vapour deposition, reduction of graphene oxide(GO) that derived from chemical exfoliation of graphite and so on. Among these methods, the electrochemical reduction of GO has been attracted more attentions due to its advantages such as relatively simple, economic, easy to control and friendly to environment. In this paper, electrochemically reduced graphene oxide(ERGO) and electrochemically reduced graphene oxide/carbon nanotubes(ERGO/CNTs) thin films were prepared by the electrochemical reduction method. The ERGO and ERGO/CNTs were characterized by scanning electron microscopy(SEM), Fourier Transform Infrared(FTIR) spectroscopy, Raman spectroscopy and X-ray diffraction(XRD) methods. The effects of electrochemical reduction conditions on the electrochemical properties of ERGO and ERGO/CNTs were investigated, and comparison of electrochemical properties between ERGO and ERGO/CNTs was also included. The main contents of this paper are as follows:1. Firstly, a drop-casting method is employed to prepare graphene oxide(GO) film,then the as-prepared GO film was electrochemically reduced to ERGO film in a Na2SO4 aqueous solution. The results indicate that the electrochemical reduction process has no obvious effect on surface morphologies of GO film, and the ERGO film show a continuous ridge-fold structure alike the GO film. It has been found that the carboxyl and epoxy groups on GO sheets significantly reduced or even removed completely after the electrochemical reduction, and other oxygen-containing functional groups(such as hydroxyl) are not be removed effectively. The electrochemical reduction process introduces five-membered and seven-membered defects structure into ERGO, and interlaminar stripping or expansion of nano sheets results in a disordered structure in ERGO. The conditions for preparing ERGO thin film by cyclic voltammetry method with better electrochemical properties are optimized. A scanning potential range from0.0 to-1.4 V, 50mv/s scanning rate, 30 scanning cycles in a 0.5mol/l Na2SO4 electrolyte solution and PH=6 are better conditions to prepare ERGO film with better electrochemical performance.2. The GO/CNTs thin film was prepared by mixing dispersion of GO and CNTs, andsubsequent drop-casting method, then the as-prepared GO/CNTs was electrochemically reduced into ERGO/CNTs in a Na2SO4 aqueous solution. The results show that carbon nanotubes uniformly distributed in the ERGO/CNTs composite, and a reticular carbon nanotube structure in composite is formed. The addition of CNTs restrains the defects formation in ERGO during the process of electrochemical reduction, but the reduction degree of GO decreases slightly. It has been revealed that a quality ratio of GO to CNTs about 50:1, scanning potential range from 0.0 to-1.4 V, 50mv/s scanning rate, 30 scanning cycles in a 0.5mol/l Na2SO4 electrolyte solution and PH=6 are better conditions to prepare ERGO film with excellent electrochemical performance.3. It has been found that both ERGO and ERGO/CNTs films store energy by electronic accessing between the adjacent layers, which results in good charge and discharge reversibility. Comparing with ERGO films, the ERGO/CNTs thin film shows high specific capacitance and better conductivity, resulting from the synergistic effect between ERGO and CNTs.