Preparation, Pore Structure Regulation And Electrochemical Properties Of Phenolic - Based Porous Carbon Nanofibers

In this paper, in order to develop electrode materials with high specific surface area and proper pore size distribution for supercapacitors, porous carbon nanofibers with high performance were prepared using resol as carbon source. Using porous carbon nanofibers as electrode materials for supercapacitors, by modifying the specific surface area and pore size distribution of porous carbon nanofibers, the effect on its electrochemical performance was discussed.Microporous carbon nanofibers with high specific surface area were successfully prepared by electrospinning, curing, carbonization and pickling process, which used TEOS as the SiO2 source. Studies demonstrated that TEOS and its hydrolysate SiO2 play a significant role in maintaining the structure of fibers. Additionally, the specific surface area and total pore volume could be obviously increased with the increase of TEOS. However, when the mass ratio of TEOS and phenolic resin was further increased, the spinning process was resistant, which result in hard fabricating process of self-standing nanofiber webs. Therefore, there must be an optimum proportion between precursor and TEOS for spinning solution. In optimum conditions, a specific area as high as 2164 m2/g, high pore volume reaching to 1.01 cm3/g and relatively narrow pore size distribution from 0.6 to 1.2 nm were achieved. While testing in 6 mol/L KOH solution, electrode materials with specific capacitance of 316 F/g, excellent rate performance and cycle performance was obtained.On the basic of SiO2 and Pluronic F127 as hard template and soft template respectively, pore structures could be easily controlled, and then hierarchical carbon nanofiber were easily synthesized. Mesoporosity can be turned by adjusting the amount of F127.With the addition of F127, the specific surface area has extently decrease but the mesoporosity increases. The pore size distribution of micropores between 0.6 and 1.2 nm for microporous carbons swifted to 0.6 and 1.8 nm for hierarchically carbons, meanwhile, the mesopore centred on 5 nm and 20 nm also can be observed. Comparing to microporous carbons, hierarchically carbons present an excellent rete performance.To avoid caustic HF in removing Si-related template, MgO and F127 were selected as hard template and soft template respectively, porous carbon nanofibers with high mesoporosity of 95% can achieve. Although, the specific surface area was decreased with the increased of mesoporosity, the specific capacitance can reach to 270 F/g at 0.2 A/g, meanwhile 186 F/g at high current density, demonstrating excellent capacitance performance and rate performance.