Practical Modeling of Heterogeneous Bundles of Single-Walled Carbon Nanotubes for Adsorption Applications:  Estimating the Fraction of Open-Ended Nanotubes in Samples

Abstract

A practical approach for adsorption modeling of heterogeneity of single-walled carbon nanotube (SWNT) bundles has been developed. The method integrates experimental analysis with grand canonical Monte Carlo (GCMC) simulation of a small probe molecule, such as nitrogen at 77 K. Using this method, it is possible for one to separately estimate adsorption inside the nanotubes, adsorption on the external surface of the bundles, and adsorptive contributions from the impurities present in samples. By introducing a scaling parameter for adsorption in the internal porous volume of the bundles, the predicted adsorption isotherm results in a near replication of the experimental N 2 adsorption isotherm. We refer to this parameter as the volume fraction of open-ended nanotubes. Our GCMC-assisted experimental characterization method has been applied successfully to several commercial samples obtained from different suppliers, such as MER Corp., Carbon Nanotechnologies Inc., Carbon Solutions Inc., Carbolex Inc., and BuckyUSA. It was found that the volume fraction of openended SWNTs in these samples ranged between 0 and 55%. The majority of the samples were subjected to some purification treatment by the manufacturer and exhibited an already high BET surface area of hundreds of square meters per gram. The near-perfect reproduction of the experimental N 2 (77 K) adsorption isotherm for each of the tested samples shows that our characterization method is not specific to a particular sample and can be extended to most SWNTs successfully. The fraction of open-ended SWNTs cannot otherwise be estimated by visual characterization of the samples because of the large aspect ratio of nanotubes and the spaghetti-like arrangement of the bundles. Our method has the potential to become a standard technique to quantify this structural property of SWNT samples.

Application of water–activated carbon isotherm models to water adsorption isotherms of single-walled carbon nanotubes

“…The sample descriptions, morphologies, and characterization details were provided in our previous work [24,25]. Briefly, the SWNT samples are labeled as SWNT1 (>95% SWNTs, from MER Corp., previously referred to as EA95); SWNT2 (>90% SWNTs, from Carbon Nanotechnologies Inc., previously labeled as CVD90); and SWNT3 and SWNT4 (70% and 80% SWNTs, from Carbon Solutions Inc., previously labeled as CS70 and CS80, respectively).…”

Aging of nanocarbons in ambient conditions: Probable metastability of carbon nanotubes

“…It was not available from the manufacturer. Our group has developed adsorption based methods to characterize the fraction of open-ended nanotubes [38]. The appropriate values are presented in Table 1.…”

Hydrogen physisorption and selectivity in single-walled silicon carbon nanotubes: a grand canonical Monte-Carlo study

“…In recent years, considerable efforts have been spent on hydrogen storage by nanotubes [1,2]. The gas storage capacity, especially hydrogen storage in micro/nano pores of nanotubes, is interested from the industrial point of view and potential application of hydrogen for fuel cell vehicles [3,4].…”