Selective oxidation of single-walled carbon nanotubes using carbon dioxide

doi:10.1016/S0008-6223(03)00054-X

Carbon

Volume 41, Issue 6, 2003, Pages 1221-1230

https://doi.org/10.1016/S0008-6223(03)00054-X Get rights and content

Abstract

A simple process for selective removal of carbon from single-walled carbon nanotube samples was developed based on a mild oxidation by carbon dioxide. The reactivity profiles of as prepared and purified nanotube samples were determined using both TG and a related analytical technique, controlled atmosphere programmed temperature oxidation (CAPTO). The complex differential rate curves for weight loss (DTG) or carbon dioxide evolution (CAPTO) could be resolved by a series of Gaussian peaks each associated with carbonaceous species of different reactivity. Comparisons were made between samples as received after preparation by the laser ablation method, after purification by nitric acid oxidation, and both of these after reaction with CO₂. The DTG of as prepared tubes had a broad major peak centered about 410 °C. Mild oxidation of as prepared nanotubes under flowing carbon dioxide at 600 °C preferentially removed more reactive carbon species leaving behind a narrower distribution about the major peak in DTG. In contrast to the as prepared material, the sample that had been purified using nitric acid had a more distinct separation of the major DTG peaks between more and less readily oxidized material. Oxidation of this sample with CO₂ selectively removed the peak associated with the most readily oxidized material. The original CO₂ oxidation experiments performed on the analytical scale were successfully scaled up to a small preparative scale.

Introduction

Partial and selective oxidation has been routinely used to modify the adsorption characteristics of activated carbons. Similar approaches might be valuable in modifying single-walled carbon nanotubes (SWCNTs). In particular, it has already been demonstrated that partial oxidation with carbon dioxide opens the ends of and “thins” multi-walled nanotubes [1] as well as increases the microporosity of soot [2] derived from arc vaporization of carbon. In fact, we have discovered that mild oxidation with CO₂ is an effective way for activating SWCNTs, thereby increasing their hydrogen storage capacity [3]. In addition to activating SWCNTs, mild CO₂ oxidation provides insight into their chemical reactivity and character. The application of thermogravimetry (TG) and related techniques is particularly valuable in this context. A comparison between samples of raw and purified nanotubes received from tubes@rice [4] is the main focus of this work. The raw material was purified by partial oxidation using HNO₃ followed by extraction and washing [5]. This technique was devised to generate high-purity SWCNTs by removing the commonly encountered contaminants: metallic catalyst, amorphous carbon, “shells”, and various fullerite structures. A recent extensive transmission electron microscopy (TEM) study of the effects of purification by treatment with strong acids has shown that typically employed purification procedures lead to partial oxidation of SWCNTs themselves and sometimes to an extensive disruption of the tubular structure [6]. We report below on the use of carbon dioxide for the selective removal of easily oxidized material from SWCNTs produced by the laser ablation method [7] and purified samples of those materials [5].

Section snippets

Experimental

SWCNT samples were purchased from tubes@rice. The “Purified” grade was received as a suspension in toluene (6 mg/ml). Samples (typically 10 ml) were withdrawn and evaporated in a stream of N₂ and then heated to 110 °C at 25 mmHg pressure for 2 h or at 140 °C for 12 h at atmospheric pressure (1 mmHg=133.322 Pa). Samples were often stored under ambient conditions for days prior to use and most received moderate grinding prior to use. “Raw Material” grade was received as a solid fibrous material and

Rice-purified SWCNTs

CAPTO analysis of purified-grade rice SWCNTs is shown in Fig. 1. The weight of carbon evolved as carbon dioxide is plotted versus temperature. The curve shows that the initial oxidation starting at 200 °C is the first of four distinguishable but unresolved peaks. The results of curve fitting (R²=0.999) and integration of the individual components are also shown. The first oxidation is centered at 297 °C and accounts for 28% of the total. The major component (67%) is centered at 368 °C and two

Summary and conclusions

Raw and purified SWCNTs produced by the laser ablation technique were analyzed by CAPTO and TG. Both analyses (Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5) reveal that despite the considerable extent of purification achieved by nitric acid oxidation, the purified sample remained a mixture of carbons of different oxidative reactivity. Comparative analyses were conducted in three atmospheres of differing oxidative reactivity—oxygen, air, and carbon dioxide. In each case, a progression of four to five

Acknowledgements

This work was performed while M.R.S. held a National Research Council–NETL Research associateship. The assistance provided by Leslie Bittner in obtaining TG data is gratefully acknowledged. Dr. J. Karl Johnson provided helpful discussions on nanotubes. Reference in this work to any specific commercial product is to facilitate understanding and does not necessarily imply endorsement by the United States Department of Energy.

References (15)

M. Monthioux et al.
Sensitivity of single-wall carbon nanotubes to chemical processing: an electron microscopy investigation
Carbon
(2001)
R.B. LaCount et al.
Advances in coal characterisation by programmed-temperature oxidation
Fuel
(1993)
D.B. Mawhinney et al.
Surface defect site density on single walled carbon nanotubes by titration
Chem. Phys. Lett.
(2000)
E.W. Bittner et al.
Characterization of the surfaces of single-walled carbon nanotubes using alcohols and hydrocarbons: a pulse adsorption technique
Carbon
(2003)
S.C. Tsang et al.
Thinning and opening carbon nanotubes by oxidation using carbon dioxide
Nature
(1993)
Tsang SC, Harris PJF, Claridge JB, Green MLHA. Microporous carbon produced by arc-evaporation. J Chem Soc Chem Commun...
M.R. Smith et al.
Hydrogen storage on carbon single-walled nanotubes

There are more references available in the full text version of this article.

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Published by Elsevier Ltd.

Selective oxidation of single-walled carbon nanotubes using carbon dioxide

Abstract

Introduction

Section snippets

Experimental

Rice-purified SWCNTs

Summary and conclusions

Acknowledgements

Carbon

Fuel

Chem. Phys. Lett.

Carbon

Thinning and opening carbon nanotubes by oxidation using carbon dioxide

Nature

Hydrogen storage on carbon single-walled nanotubes