Preparation And Electrochemical Performance Of Carbon Nanomaterials By Pyrolysing Organics

Since a long time,carbon nanomaterials have been a hot point in the fields of material research due to its low production and processing costs,good electroconductibility and mechanical capacities,large specific surface area and modifiability.Firstly,we synthesized the Ni(C5H5N)4 complex by using nickel nitrate and pyridine as raw materials,then the nitrogen-doped carbon nanotubes were prepared by tube-sealing pyrolysis or pyrolyzed under atmospheric pressure in N2 atmosphere.We found that during 600-900?the optimum technological parameters of tube-sealing pyrolysis was achieved as follows:the carbon nanotubes with 2.31%nitrogen doping content can be prepared with the carbonization temperature of 700?maintaining 12h at a rate of 10? min-1,the average diameter is about 25.6 nm and average inside diameter is about 12.2 nm.Carbon nanotubes with 0.82%nitrogen doping content can be prepared with the carbonization temperature of 900? maintaining 8h at a rate of 10?min-1,the average diameter is about 25.9 nm and average inside diameter is about 13.9 nm.As the growth of carbon nanotubes follows the gas-liquid-solid(VLS)mechanism,and tube-sealing pyrolysis can promote the self-deposition of small molecule carbon source,it can prepare high-quality nitrogen-doped carbon nanotubes than the atmospheric pressure pyrolysis method.Electrochemical tests showed that under the current densities of 50 and 500 mA g-1,the CNTs prepared by tube-sealing pyrolysis with the carbonization temperature of 700? maintaining 12h showed a capacity increase,and the specific capacity could still be maintained at 683.5 mAh g-1 and 437.1 mAh g-1 after 100 cycles.About the CNTs prepard by pyrolyzed under atmospheric pressure with the carbonization temperature of 900? maintaining 8h,the specific capacity are 471.6 mAh g-1 and 357.7 mAh g-1 after 100 cycles.Subsequently,a kind of Sea urchin-like carbon nanofibers was prepared by injecting pyrolysis with ferrocene and benzene as the reaction solution.The optimum technological parameters of injecting pyrolysis was achieved as follows:the carbonization temperature is 1050?,using thiophene as cocatalyst,its concentration is 0.5(S/Fe atom ratio),the reaction time is 0.5 h,catalyst concentration range is 0.025-0.1 g/ml,and the maximum yield of sea urchin-like carbon nanofibers is about 47.6%.By comparing the carbonized products prepared by injecting pyrolysis with benzene,pyridine and dichloromethane as solvents,benzene as solvent can form a unique structure of sea urchin carbon nanofibers,and the other two solvents can form iron carbon composite spheres.Under the current density of 50 mA g-1,the specific capacity of sea urchin-like carbon nanofibers with three different concentrations(0.025 g/ml,0.05 g/ml,0.1 g/ml)were maintained at 368.7 mAh g-1,218.5 mAh g-1,273.5mAh g-1 after 100 cycles.Under the current density of 1A g-1,the specific capacities are 320.1mAh g-1,191.4mAh g-1,286mAh g-1 after 100 cycles,which also indicates that the material has good rate performance and excellent cycling stability.In this study,based on the tube-sealing pyrolysis method and injecting pyrolysis method,the nitrogen-doped carbon nanotubes and sea urchin-like carbon nanofibers were prepared successfully.Also we discussed the influence of process parameters which will change the morphology of carbonized products during the carbonation process,which have important guiding significance for the preparation of other carbon materials.