Preparation And Electrochemical Performance Of Mesoporous Carbon And Carbon-Based Composites

In order to avoid the energy depletion, considerable research efforts have been focused on alternative energy conversion and storage systems with high efficiency, low cost and environmental benignity. Supercapacitors ?SCs?,also known as electrochemical capacitors?ECs?,have received a considerable amount of attention due to their attractive merits,such as higher power density,faster charge/discharge process,and longer cycle life,which can be applied in the field of electric vehicles, electronic devices, and other power supply facilities. It can be widely used in areas of mobile communication, transportation, aerospace and defense science and technology. Among all the components of capacitor, electrode material plays a decisive role in the electrochemical performance of supercapacitors. The electrode materials usually contain carbon materials, metal oxides and conducting polymers. The carbon materials and their composite materials as supercapacitors electrode material has been widely research and attention. However, carbon-based materials with simple synthesis method, excellent capacitance performance and low cost need further exploration. Herein, we have designed and prepared mesoporous carbon materials and graphene-based composites and analyzed their electrochemical properties. The main contents are summarized as follows:Uniform fibrous-structured hollow mesoporous carbon spheres ?FHMCSs? have been synthesized by a simple template method using fibrous-structured mesoporous silica microspheres and resol precursor as silica template and carbon sources, respectively. It is found that FHMCSs have an ultra high specific surface area of 1121 m² g^-1 and large pore volume of 1.3 cm³ g^-1. The high surface-to-volume ratio is a favorable factor to obtain high specific capacitance and excellent rate performance. As expected, when used as supercapacitor electrodes,the FHMCSs exhibit high specific capacitance of 359.2 F g^-1 at current density of 1 A g^-1 and excellent cycle stability ?92% retention after 5000 cycles?. The reason for this superior performance may be that the FHMCSs with interesting fibrous-structure is beneficial to the mass transfer during the electrochemical process, suggesting a potential application in supercapacitors and other energy storage fields.A series of cobalt nanoparticles/reduced graphene oxide ?Co/RGO? composites have been successfully synthesized via an in situ crystal growth method under solvothermal conditions for the first time. The synthesized composites are comprised of Co particles that are uniformly anchored onto the surface of graphene sheets by in situ reducing. Powder X-ray diffraction?XRD?, Raman spectroscopy, Scanning electron microscopy ?SEM?,Transmission electron microscopy ?TEM?, X-ray photoelectron spectra ?XPS?, and Brunauer-Emmett-Teller ?BET?analysis are performed for systematically characterizing the microstructure and composition of the as-prepared Co/RGO composites. Interestingly, the as-prepared composites show superior electrochemical performance. As a result, Co/RGO composite exhibits a high specific capacitance of 321.7 F g^-1 at 1 A g^-1 in 2 M KOH aqueous solution as well as good rate capability. Meanwhile, the capacitance retention keeps about 90% of the initial value after 2000 cycles at a current density of 2 A g^-1. The excellent electrochemical performances are due to the 3D graphene conductive network and the synergetic effect of RGO and Co particles,suggesting that Co/RGO composite possesses a great potential application in supercapacitors.