Effect of alignment on adsorption characteristics of self-oriented multi-walled carbon nanotube arrays

Abstract

The adsorption characteristics of self-oriented multi-walled carbon nanotube (MWCNT) arrays are examined from N2 (−196 °C) adsorption measurements. The arrays were synthesized in a laboratory by in situ chemical vapour deposition of iron or cobalt phthalocyanines at 880 and 950 °C, under otherwise constant conditions, in an attempt to obtain different morphological structures. For both precursors, increasing the temperature leads to MWCNT arrays with lower Brunauer–Emmett–Teller (BET) surface area and total pore volume, though the effect is more pronounced for those arising from the iron-based compound. Despite this, precursor yields of individual nanotubes of larger diameter, higher BET area and total pore volume characterize the resulting arrays compared to those arising from cobalt phthalocyanine for the same temperatures. As evidenced by SEM and TEM images, the arrays synthesized from iron phthalocyanine at 880 °C show better vertical alignment and denser structures than those obtained from this compound at 950 °C, and also from cobalt phthalocyanine at both temperatures. Further ultrasonication of the arrays produced from the iron compound brings about a significant reduction in their adsorption capacity, attributable to the pronounced disarrangement of the resulting structures. The present results demonstrate that the alignment of MWCNT arrays plays a crucial role in their N2 adsorption characteristics.

Carbon nanotubes as adsorbents in environmental pollution management: A review

“…The 'carbon islands' and their surrounding defects and cavities may be efficient hydrogen adsorption sites of MWCNTs, and the exposed carbon edges have great effect on hydrogen storage in MWCNTs. Zilli et al [116] examined the adsorption characteristics of self-oriented MWCNT arrays using N 2 (−196 • C) adsorption measurements, and found that the diameter of the individual nanotubes forming the arrays might be not the prevalent characteristic for the N 2 adsorption behavior of the arrays. Instead, they showed that alignment played a crucial role.…”

Carbon Nanotube Supercapacitors

“…First, aligned CNTs are better-structured materials for supercapacitors. Unlike the irregular pore structures of randomly entangled CNTs (Fig.3a), the vertically aligned and unbundled structures and the well spacing between tubes of the aligned CNTs (Fig.3b) provide a more mesoporous and more accessible surface (Zilli et al, 2006). The aligned structures should provide improved charge storage / delivery properties as each of the constituent aligned tubes can be connected directly onto a common electrode, i.e., participation of each tube during the charge / discharge process of the capacitor.…”

“…Unique properties of plasmaetched, vertically aligned CNTs developed in our work are believed to be responsible for their superior capacitance in the ionic liquid. First, the vertically aligned and unbundled structures and well spacing between tubes of the aligned CNTs (Fig.12) provide a mesoporous and accessible surface (Zilli et al, 2006), resulting in a high electrolyte accessibility, a large effective surface area, and thus a strong capacitive behavior for the aligned CNTs. Second, plasma etching can effectively open the end tips of the nanotubes (Fig.12d) (Huang et al, 1999;Huang & Dai, 2002).…”

Growth of Manganese Oxide Nanoflowers on Vertically-Aligned Carbon Nanotube Arrays for High-Rate Electrochemical Capacitive Energy Storage

“…CNTA is excellent for electrodepositing transition metal oxides because of its regular pore structure, high surface area, homogeneous property (binderfree), and excellent conductivity. [27][28][29][30] The experimental results show that the manganese oxide/CNTA composite electrode exhibits superior rate performance (50.8% capacitance retention at 77 A/g) in an EC, thus, making it very promising for high-rate electrochemical capacitive energy storage applications.Our strategy is shown schematically in Figure 1. The preparation of manganese oxide/CNTA composite mainly involves (1) growing a vertically aligned CNTA on a Ta foil directly by chemical vapor deposition at 800°C 31 and (2) electrodepositing manganese oxide on CNTA "scaffold"…”