Jingli Shi

Nitrogen-doped hierarchical porous carbon with high surface area derived from graphene oxide/pitch oxide composite for supercapacitors

A nitrogen-doped hierarchical porous carbon has been prepared through one-step KOH activation of pitch oxide/graphene oxide composite. At a low weight ratio of KOH/composite (1:1), the as-prepared carbon possesses high specific surface area, rich nitrogen and oxygen, appropriate mesopore/micropore ratio and considerable small-sized mesopores. The addition of graphene oxide plays a key role in forming 4 nm mesopores. The sample PO-GO-16 presents the characteristics of large surface area (2196 m(2) g(-1)), high mesoporosity (47.6%), as well as rich nitrogen (1.52 at.%) and oxygen (6.9 at.%). As a result, PO-GO-16 electrode shows an outstanding capacitive behavior: high capacitance (296 F g(-1)) and ultrahigh-rate performance (192 F g(-1) at 10 A g(-1)) in 6 M KOH aqueous electrolyte. The balanced structure characteristic, low-cost and high performance, make the porous carbon a promising electrode material for supercapacitors.

Preparation and molten salt-assisted KOH activation of porous carbon nanofibers for use as supercapacitor electrodes

Carbon nanofiber paper was prepared by electrospinning from thermosetting phenolic resin, followed by activation via KOH-containing molten salt at high temperature. By adding a small dosage of KOH in the molten salt the porous volume and specific surface area could be greatly improved. The obtained porous carbon nanofibers had a specific surface area of 1007xa0m2xa0g−1, total pore volume of 0.363xa0cm3xa0g−1, micropore volume of 0.247xa0cm3xa0g−1. The electrochemical measurements in 6xa0M KOH aqueous solution showed that the porous carbon nanofibers possessed high specific capacitance and considerable rate performance. The maximal specific capacitance of 288xa0Fxa0g−1 was achieved at 0.2xa0Axa0g−1 and the specific capacitance could still remain 204xa0F g−u20091 at 20xa0A g−1 with the retention of 71%. In the molten salt system, the reaction between activating agent and carbon could be more efficient, hence, such molten salt-assisted activation method was considered as a general activation method for the high-specific-surface-areaed carbons.

Preparation and one-step activation of nanoporous ultrafine carbon fibers derived from polyacrylonitrile/cellulose blend for used as supercapacitor electrode

In this work, nanoporous ultrafine carbon fibers have been fabricated by one-step activation of electrospun polyacrylonitrile (PAN)/cellulose acetate (CA) ultrafine fiber using ZnCl2 as an activation agent. CA, a renewable resource, was used to replace part of PAN as carbon precursor for electrospun carbon fibers. The effect of additive amount of CA on the microstructure of the ultrafine carbon fibers, including morphology, crystal structure, porosity, specific surface area and surface chemistry, has been investigated. The introduction of CA made an active role in improving structural stability and specific surface area. Both three-electrode and two-electrode test were conducted to evaluate capacitive performance of the ultrafine carbon fibers. And the correlation between electrochemical performance and structure of the carbon fibers was discussed. When CA/PAN mass ratio was 1:9, the ultrafine carbon fibers have the highest specific capacitance of 280xa0F/g. Such high specific capacitance should be due to combination of high content of surface functionality and wider pores.

Preparation of diameter-controlled multi-wall carbon nanotubes by an improved floating-catalyst chemical vapor deposition method

Abstract Multi-wall carbon nanotubes (MWCNTs) with controlled diameters were synthesized by an improved-floating catalyst chemical vapor deposition method, using toluene and ferrocene as a carbon source and catalyst precursor, respectively. Ferrocene was sublimed in a heater and carried as a gas mixed with toluene vapor into a reactor where MWCNTs were formed. The effects of the sublimation temperature, hydrogen content in the gas mixture and gas flow rate on the diameter and diameter distribution of the CNTs formed were investigated. Results indicated that the CNT diameter distributions could be controlled by changing the sublimation temperature. The higher the sublimation temperature, the narrower the distribution of CNT diameters. The average CNT diameter decreased and levelled off with increasing hydrogen content in the gas mixture from 0 to 40 vol%. The CNT diameter decreased with increasing gas flow rate.

Preparation and Comparative Study of Microporous and Mesoporous Carbon Nanofibers as Supercapacitor Electrodes

Microporous carbon nanofibers (Mi-CNFs) and mesoporous carbon nanofibers (Me-CNFs) with high surface area were prepared by electrospinning resol resin/PVP/TEOS/F127 ethanol solution, followed by curing, carbonization and pickling process. TEOS was responsible for structural stability and producing micropores, while F127 for forming mesopores. Mi-CNFs showed high specific surface area of 1841 m2 g-1, while Me-CNFs possessed both high specific surface area of 1674 m2 g-1 and mesoporosity of 64%. The electrochemical test revealed that Mi-CNFs had higher capacitance (276 F g-1 at 0.5 A g-1) and Me-CNFs possessed higher capacitance retention (71%, 150 F g-1 at 30 A g-1).