The Study Of Supercapacitive Properties Of Graphene Based Composite Electrodes

In response to the increasingly serious energy crisis and extensive use of power by modern science and technology society, people put more and more interests in hydroenergy, wind energy, solar power and other renewable clean energy as alternatives to the oil, coal and other disposable energy. Meanwhile, it is essential to find the solution for the storage of green energy, which plays a crucial role in the development of global economy and human life. Supercapacitor, also called electrochemical capacitor, is regarded as a new generation of energy storage device due to its promising properties, such as long cycle life, high security, wide work temperature range and no pollution. To solve the problems, such as coal consumption, oil imports, lead-acid battery pollution and vehicle exhaust pollution, the government positively promotes the use of supercapacitor. Therefore, currently the study on the basic theory and applications of supercapacitor is necessary.Recent years, it has been reported that graphene was used as electrode material for supercapacitor due to its extraordinary properties caused by the unique2D structure, such as excellent chemical stability, high conductivity and large specific surface area. Although the lack of effective synthesis method will limit its promising applications, graphene still raises a new technological revolution in electronics, information, biomedicine and especially energy storage areas, due to its good photoelectric and mechanical properties. The main content in this paper includes following parts:1. Graphene, sythesized by reduction processes via N2H4or microwave-heating in alkaline solution and acidic solution, respectively, was comparatively characterized as supercapacitor electrode material.2. Graphene and graphene-metal oxide (ZnO and SnO2) composites were prepared by screen printing and ultrasonic spray pyrolysis (USP) methods, meanwhile, the electrochemical properties were studied. The results indicated that graphene and ZnO or SnO2nanoparticles had a good synergistic effect, therefore the specific capacitance and power density of the composite had been increased. The specific capacitance of graphene-ZnO and graphene-SnO2reached the highest value when the deposition time of metal oxides was5min.3. Graphene-carbon nanotubes (CNTs) composite films, used as supercapacitor electrode materials, were successfully fabricated by electrophoretic deposition. The electrochemical performances of films were analyzed through cyclic voltammetry and chronopotentiometry tests. The results showed that graphene-CNTs composite with40%CNTs exhibited an optimal electrochemical capacitance compared with pure graphene and CNTs, due to a synergistic effect of graphene and CNTs.4. Graphene-ZnO nanocomposite was successfully one-step synthesized via microwave-heating reduction in a microwave synthesis system. The electrochemical performance of the composite was analyzed through cyclic voltammetry and chronopotentiometry tests. The results showed that as compared with pure graphene, graphene-ZnO composite exhibited an improved electrochemical capacitance and excellent reversible charge/discharge behavior.