Hole Opening of Carbon Nanotubes and Their Capacitor Performance

Abstract

Pore structures and electrochemical performances of mass-produced metal-free single-walled carbon nanotubes (mf-SWCNTs) heated in either CO 2 gas or dry air were investigated. Pore structures, defects, and electrochemical performances of mf-SWCNTs were analyzed mainly using the N 2 adsorption method, apparent density measurement, Raman spectroscopy, and cyclic voltammogram. mf-SWCNT sheets heated in CO 2 gas showed a remarkable increase of the specific surface area up to 1900 m 2 g -1 , but sheets heated in air showed an increase of only up to 1400 m 2 g -1 . Propan-2-ol, 4-methyl-1,3-dioxolan-2-one, or ionic liquid was impregnated in the inner space of mf-SWCNTs to confirm whether the inner space of mf-SWCNTs is filled with each liquid. mf-SWCNTs heated in air were completely filled, but mf-SWCNTs heated in CO 2 were partially filled. From these results, it is estimated that holes of the size of 0.56 nm or larger are opened on the side wall of mf-SWCNTs. A combination of two heat treatments maximized the effective specific capacitance of heated mf-SWCNTs up to 100 F g -1 , which is 1.6 times higher than that of as-grown mf-SWCNTs because of the removal of the carboneous component and the creation of defects on the sidewall of mf-SWCNTs, which allow the electrolyte into the inner space of mf-SWCNTs.

Facile synthesis of MnO2/CNT nanocomposite and its electrochemical performance for supercapacitors

“…Supercapacitors, based on the charge-discharge mechanisms, can be classified into two kinds. The first one is called electrical double-layer capacitors (EDLCs), including various carbon materials [4][5][6][7][8][9] with high specific surface area such as activated carbon, carbon nanotubes and graphene, which utilize the capacitance arising from charge separation at the electrode/electrolyte interface. The other one is called pseudo-capacitors, including transition-metal oxides [10][11][12] and conducting polymers [13][14][15], which utilize the pseudo-capacitance arising from the fast, reversible redox reaction occurring at the electrode surface.…”

In Situ Synchrotron X-ray Diffraction Studies of Single-walled Carbon Nanotubes for Electric Double-layer Capacitors

“…(2) expresses the surface ratio of bundle surface area S out to the tube inner surface area S in as a function of number (N) of tubes in a bundle. (2) where, r vdw is a van der Waals radius of carbon atom. According to Eq.…”

“…Therefore, there is a strong demand to develop new electrode materials to improve the energy density of EDLC. SWCNTs (Single-walled carbon nanotubes) have been expected as a good electrode material for EDLC because the theoretical specific surface area of SWCNTs is very large (2,630 m 2 /g) [1][2][3][4]. However, the reported EDLC capacitance values of SWCNTs are not so high compared to the values of the typical EDLC electrodes (e.g.…”

Enhancement of electric double layer capacitance of carbon nanotubes by gallium ion irradiation

“…14 The upshift in the G-band is caused by stress generated in MWCNTs after Ga þ ion irradiation. 18 HRTEM image shown in the inset of Fig. Third, the presence of the 2D graphene structure in the sample can be monitored by the nature of the G 0 -band in the Raman spectra.…”