CO₂-Assisted SWNT Growth on Porous Catalysts

Abstract

The effect of CO 2 on the synthesis of single-walled carbon nanotubes (SWNTs) by methane decomposition on a Fe/Mo/MgO porous catalyst was investigated. Characterizations of the change in methane conversion with time, XRD and SSA of the catalyst, Raman spectroscopy, TGA, and the specific surface area (SSA) of SWNTs showed that CO 2 inhibited the formation of amorphous carbon around the catalyst and also interacted with the MgO support of the catalyst, which decreased its particle size and increased the SSA of the catalyst. The result was an increase in the yield, purity, and SSA of SWNTs. These results indicated that the limited and small space in the pores of the porous catalyst made it difficult to increase the SWNTs in high yield. The addition of CO 2 , by destroying the structure of the catalyst and decreasing the catalyst size, provides a new route to increase the yield, purity, and SSA of SWNTs.

Synthesis of High‐Quality, Double‐Walled Carbon Nanotubes in a Fluidized Bed Reactor

“…However, to date, their mass production remains a challenge, whether using laser-ablation, arc-discharge or chemical vapor deposition (CVD) methods. Compared with the two former methods, CVD has potential advantages in producing DWCNTs, single-walled carbon nanotubes (SWCNTs) or their mixtures with high selectivity at a small scale of milligrams to grams [3][4][5][6][7][8][9][10][11]. However, the mass production of DWCNTs is hardly reported.…”

“…Though some reports have discussed the mass production of SWCNTs [12][13][14], they may be different for DWCNTs. Recent study suggests that the wall number control of SWCNTs is relatively tough as compared to that of multi-walled carbon nanotubes (MWCNTs) [10,11]. In this case, the higher metal loading on the catalyst for the DWCNT growth than that for the SWCNT growth makes it more difficult to avoid sintering than for the latter, when operated in the same high temperature range.…”

“…In this case, the higher metal loading on the catalyst for the DWCNT growth than that for the SWCNT growth makes it more difficult to avoid sintering than for the latter, when operated in the same high temperature range. Moreover, to synthesize bulk DWCNTs, it is necessary to control the concentration of the carbon source and the gas velocity [14], the thermal stability of the catalyst [10,11], the contact time of the catalyst with the carbon source [12], as well as the agglomerate structure of the carbon products [14] so that these are similar to those in the synthesis of MWCNTs [15][16][17][18][19].…”

Recent Progress on the Growth Mechanism of Carbon Nanotubes: A Review

“…Hydrothermal treatment of Fe/MgO, as well as the addition of CO 2 during the SWCNT synthesis, have both been shown to increase the porosity of the catalyst and, consequently, the amount of active phase in contact with the reaction feed, leading to higher yields. [190][191] After analyzing these experimental results, one might discuss whether the same explanations also apply to Fe/Al 2 O 3 . In the case of powder catalysts, boehmite, which is an aluminum oxide hydroxide, is often chosen as a support.…”

A Comparative Study of Cobalt Catalyst Behavior between Silica and Quartz Substrates for Single-Walled Carbon Nanotube Growth

“…Typically, insulating materials, such as silica [10][11][12], alumina [8,9,13,14], magnesia [15][16][17], quartz crystal [18,19], etc., have been successfully used as catalyst supports in SWNT synthesis. To some extent, the main structure difference of the substrates above can be attributed to amorphous and crystalline configuration of the surfaces.…”