Preparation Of Mesoporous Carbon Materials And Their Applications In Supercapacitors

Supercapacitors have been extensively studied due to their low price,fast charge/discharge speed,high power density,and good cycle stability.Among them,the choice of electrode materials has a very critical factor on the performance of supercapacitors.Among many electrode materials,mesoporous carbon materials are widely used in supercapacitors due to their large specific surface area,rich mesoporous structure and good electrochemical performance.The presence of mesopores provides a powerful condition for the transport of the electrolyte.In this paper,the selection of templates,the way of synthesis and the influence of heteroatom doping on carbon materials were explored,and the electrochemical performance of mesoporous carbon was improved.The main researches of the thesis are as follows:1)A novel"pyrolysis-deposition"method is proposed.The waste plastic material polystyrene?PS?is converted to ordered mesoporous carbon?OMCs?.During the synthesis process,PS is pyrolyzed into small organic gases under high temperature,which is then adsorbed through capillary adsorption into the mesoporous of SBA-15 in presence of the catalyst.The obtained ordered mesoporous carbons have high specific surface area,uniform pore size and ordered pore structure.OMCs exhibit specific capacitance of 118 F g^-1 at current density of 0.2 A g^-1,and electrochemical stability of 87.2%at current density of 2 A g^-1 after 5000 cycles.The“pyrolysis-deposition”strategy provides a new idea to convert waste plastics into high-performance carbon materials for electrochemical applications.2)Nitrogen-doped mesoporous carbon?N-MC?was successfully prepared.Tetraethyl-orthosilicate is hydrolyzed and self-polymerized to form mesoporous silica.Meanwhile,aniline monomer is adsorbed and polymerized in the channel of mesoporous silica under the catalysis of iron.After removing silica and iron species,the resulting N-MC has rich nitrogen,mesoporous structure and large specific surface area(1172 m²g^-1).As an electrode material,in 6 M KOH aqueous solution in a three-electrode system,N-MC exhibits an excellent specific capacitance of 334.5 F g^-1 at 0.5 A g^-1 and has good cycle stability?88.5%after 5000 cycles?at 5 A g^-1,maintaining 81.1%of the original capacitance even at high current densities,demonstrating the enormous potential of N-MC in supercapacitor applications.3)The N,O co-doped ordered mesoporous carbon?N/O-OMC?were successfully prepared by the solid-solid grinding method using KIT-6 as template,Fe?NO3?3 as catalyst,and polyvinylpyrrolidone?PVP?as source of C,N,and O.The effect of amount of PVP on the structural parameters of the sample was also discussed.The resulting N/O-OMC replicated the morphology of KIT-6 and showed suitable N and O doping,a large specific surface area and an ordered dual-mesoporous structure.Due to the introduction of N and O,the wettability of the electrode material in the electrolyte is improved.As the electrode materials,N/O-OMC exhibited excellent specific capacitance of 229 F g^-1 at 1 A g^-1,excellent rate performance?79.5%?and cycle stability?92.3%after 5000 cycles?.This multi-element doped mesoporous carbon material was proved a good candidate for high-performance electrode materials.