The Synthesis Of Carbon-based Nano Composite And Their Application In Supercapacitor

In order to resolve the depletion of fossil fuels and environmental pollution, much attention has been paid to develop a kind of renewable and clean energy conversion/storage systems in recently years. Supercapacitor is also known as electrochemical capacitors, which is a new kind of electrochemical storage device between traditional capacitor and battery. Compared to traditional batteries, supercapacitor possesses lots of merits such as high power density, long cycle life and environment-friendly, making supercapacitor become a potential competitor as energy storage devices in a wide range of applications. Though supercapacitor has high theoretic capacitance, long cycle-life and very fast charging and discharging process, the practice properties of supercapacitor are much less than that the theoretic one due to the lower conductance and small specific surface area of the electrode materials. Thus how to obtain electrode materials with low resistance and high specific surface area has been identified as a major challenge for the practice application of supercapacitors. In this work, firstly we have prepared nanographene sheet and3D carbon nanotube foam with greenhouse gas CO2as a raw material by a simple and environmental method and then based on these carbon materials, some composite electrode materials with high electrochemical performance are obtained. The main results are listed as follows:1. We have synthesized nanographene sheet (NGs) hybrid α-MnO2nanotube (MTGs) and α-MnO2nanoparticle (MPGs) by a joint method of burn-quench and hydrothermal. The NGs are prepared by directly reverting CO2through a burn-quench method. The results indicate that these nano-carbons can easily react with KMnO4to produce MPGs even at40℃and MTGs at140℃, respectively. The electrochemical measurements show the MTGs and MPGs have excellent electrochemical properties as supercapacitor electrode materials. The specific capacitance values for the MPGs and MTGs can get up to about171.3and290.6F g-1at current density of1A g-1in1M Na2SO4electrolyte, respectively. Moreover, after3000cycles at a rate of1A g-1, the corresponding specific capacitances are150.6F g-1for MPGs and265.4F g-1for MTGs materials, which reveals the good retention of capacity upon cycling. 2. We reported the direct synthesis3D carbon nanotube foam (CNTF) macrostructure by conversing CO2through template-directed chemical vapor deposition. Using this unique network structure and outstanding electrical and mechanical properties of the CNTF, as an example, we demonstrate the excellent electrochemical properties of Ni(OH)2/CNTF composite. Based on the total mass of the electrode, as high as specific capacitances of259and131F g-1are obtained at current densities of0.5and10A g1respectively. Meanwhile, the electrode also exhibits excellent long cycle life along with94.0%specific capacitance retained after2000cycle tests.