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Electrochemical Performances Of Activated Carbon And Carbon Nitride Doped By Graphene Oxide And Carbon Nanotubes

Posted on:2015-04-20Degree:MasterType:Thesis
Country:ChinaCandidate:X J YuFull Text:PDF
GTID:2272330431493047Subject:Chemical Engineering and Technology
Abstract/Summary:PDF Full Text Request
Because of the growing shortage of oil resource, and the serious pollutionfrom disel-engine exhaust of burning oil, the new energy devices, instead of oil,have still been researched. Furthermore, the power sources are paid greatattention and the greater progress has been made. Supercapacitors possessexcellent electrochemical properties, which will partially or completely substitute thetraditional oil for vehicles in traction and start-up. Besides, Supercapacitors havemuch wider applications than the traditional power sources. It is of great practicalvalue and theoretical significance to develop electrode materials with high specificcapacity for supercapacitors.At present, carbon materials for supercapacitors, such as activated carbon (AC),mesoporous carbon, carbon fibres, carbon nanotubes (CNTs), and graphene et al, arewidely investigated. But these carbon-based materials have their own shortages. CNTsand graphene, as a new type of carbon materials, have attracted much attention.Although CNTs and graphene are composed of the graphite layer, and present theperformances of batter electrical conductivity and thermal conductivity, their densityis far less than that of other carbon materals. If CNTs or graphene is added inside ACelectrodes, their superior properties will be held. With the improvement ofconductivity of the electrode materials, the higher energy density and power densitywill be gotten.Carbon nitride is the crystal material synthesized by manpower, which shows thestructures similar to graphitic layer, higher specific surface area, stronger adsorptionability and batter thermal stability. These properties have attracted worldwideattention due to their potential application in mechanism, optics and electricalmarerials. The main studies of this paper as follows:(1) The Hummer method was used to prepare the graphene oxide, and thepreparation conditions were optimized. The results show that the contents ofpotassium permanganate and sulfuric acid have the most influences on themorphology of the graphene oxide. The graphene oxide presents the aggregationwhen the contents of potassium permanganate and sulfuric acid were insufficient orsufficient. The electrochemical performances reveal that the graphene oxide has battercapacitance characteristic, batter performances of power discharge and cyclibility.(2) After the CNTs and graphene oxide were added inside activated carbon, theinfluence of the conductivity of activated carbon electrodes on the electrochemicalperformances was explored. The results of electrochemical capability reveal that the effect of the CNTs and graphene oxide on the conductivity is similar. The conductivityof the activated carbon electrodes increases with the increase of the content of theCNTs and graphene oxide inside the activated carbon. The best capacitancecharacteristic, the highest response current density and capacitance are achieved whenthe CNTs and graphene oxide of5wt%are used. Furthermore, the differences of theirelectrochemical performances are also compared. The effect of CNTs on theelectrochemical performances of activated carbon electrodes is superior to that ofgraphene oxide.(3) The bulk C3N4and“graphitic”(g)-C3N4with a layered structure wereprepared by dicyandiamide as the precursor. CNTs was “in situ” combined with g-C3N4as the electrode materials of supercapacitors. Their electrochemical propertieswere analyzed. The results demonstrate that N2adsorption volume increases with theincrease of CNTs added. The best electrochemical performances are found whenCNTs of50wt%are added in the bulk C3N4. Whereas the best electrochemicalperformances appear at CNTs of25wt%are added in the g-C3N4. Therefore, g-C3N4with a layered structure will be superior to the bulk C3N4in the application.
Keywords/Search Tags:Supercapacitor, Graphene Oxide, Carbon Nanotubes, Carbon Nitride
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