Effect of Purification on Pore Structure of HiPco Single-Walled Carbon Nanotube Aggregates

Abstract

HiPco single-walled carbon nanotube (HPNT) containing Fe was purified by one-step purification with HCl-washing (D-method) and two-step purification with HCl-washing after air oxidation (GD-method). The N 2 adsorption isotherm of HPNT at 77 K is of type II and it changes to type IV after purification. Purification by the D and GD methods increases the total surface area and micropore volume, and it decreases the average pore width from 3.5 nm to 1.7 and 1.0 nm, respectively.Introduction. Carbon nanotubes, 1 which are one of the recently discovered novel carbon nanomaterials, have received much attention both from scientific and technological aspects and they are expected to hold a great potential for application in various fields. In particular, the reversible storage of hydrogen on carbon nanotubes has been studied extensively. [2][3][4] Because the pore structure of carbon nanotube aggregates plays an essential role in gas adsorption, it is necessary to determine accurately the pore structure of carbon nanotube. The single-walled carbon nanotubes (SWCNTs) with catalytic method contain metallic impurities such as Fe, Ni, and Co in addition to various forms of carbon such as graphite, amorphous carbon, and nanoparticles. [5][6][7] These authors have studied gas adsorption using single-walled carbon nanohorns (SWNHs) which can be obtained in a pure form. 8,9 As SWNH has a slightly different morphology from SWCNT, we need highly pure SWCNTs to understand the gas adsorption properties exactly. A better purification method must be developed in order to study intrinsic properties of carbon nanotubes. Hence, various purification techniques for carbon nanotubes have been reported. [10][11][12][13] However, many purification methods such as chemical and mechanical treatments give rise to structure change of carbon nanotubes. Yudasaka et al. reported that metal content of HiPco SWCNT (HPNT), which was about 30 wt. %,

Mesoporous binder-free monoliths of few-walled carbon nanotubes by spark plasma sintering

“…The CNT powders exhibit a N 2 sorption isotherm ( volumes (1000-2500 m 2 /g) in line with other reports for thin MWCNTs [35], DWCNTs [15,36] and SWCNTs [37,38]. The shape of the isotherm and specifically the presence of the hysteresis loop points to a type IV isotherm, one of the six types of isotherm recognized by the IUPAC classification and characteristic of mesoporous adsorbents (i.e., the pore size diameter is in the range 2-50 nm) [39].…”

“…9) show two more or less defined micropore ranges, 0.5-1.0 nm and 1.4-1.9 nm. This could reflect a partial opening of the CNTs [37]. The present values for S BET and pore size distribution are in line with the values reported for carbon monoliths for non-activated carbon (KOHactivation is known to increase the specific surface area and microporosity) and possible applications could be as oil or gas sorbents [16,[48][49][50].…”

Activation routes for high surface area graphene monoliths from graphene oxide colloids

“…The samples were pre-evacuated at 473 K for 3 h before N 2 adsorption. The total surface area and external surface area were determined by the subtracting pore effect (SPE) method using high resolution α s -plot of the N 2 adsorption isotherm [21,22]. The surface area was also determined according to the Brunauer-Emmett-Teller (BET) method in a relative pressure range of 0.05-0.30 for comparison, although the BET analysis gives an overestimated surface area.…”

Development of Metal-impregnated Single Walled Carbon Nanotubes for Toxic Gas Contaminant Control in Advanced Life Support Systems

“…The total bet surface area of raw HiPco is 577m2/g which compares with a value of 524 mz/g for HiPco material previously reported by Yang et ai. [9].any minor differences in the raw material properties between our data and those of 31 and [9] may be attributed to batch-to-batch variations of a process that is constantly undergoing improvements, Remarkably the total surface area of our completely purified sample is 1587 m2/g which is nearly twice that of the previous best values for HiPco or other SWNT's (861 m2/g in 191). If the DMF/EDA treatment is skipped and only the acid treatment/wet oxidation is performed, we only see a total area of 968 m?g.…”