Growth and Characterization of Carbon Nanotube Carpets for Electrochemical Applications
- Category: Energy, Nanotechnology
- Tags: Carl Thompson
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Download as PDFImprovements in electrochemical devices for energy storage (Li-based batteries and ultracapacitors), and capacitive deionization are being aggressively investigated. There are many benefits to fabricating nanostructured electrodes for these devices [1] . Carbon nanotube (CNT) arrays show immense promise as electrodes due to the high aspect ratios, electrical conductivity, and mechanical rigidity of CNTs.
Carbon nanotubes are typically grown using transition metal catalysts, such as Fe. The catalyst morphology has a direct influence on the resulting nanotube diameter and areal density. We have demonstrated control of catalyst-coarsening by changing the time of the introduction of H2 during CVD growth for nanotubes grown on insulating substrates [2] . This technique allows the modulation of tube properties and carpet morphology. Additionally, we have demonstrated low-temperature growth on conductive substrates, enabled by gas preheating [3] and rapid sample insertion into the growth zone in concert with an appropriate catalyst-substrate combination [4] . An example of crystalline tubes grown on conductive substrates is shown in Figure 1.
In order to explore the effect of carpet structure on electrochemical device performance, we can mechanically densify nanotube carpets using a technique developed by Wardle et al [5] . Further, we have developed a process for transferring carpets, grown on insulating substrates, to arbitrary conductive substrates as illustrated in Figure 2. In addition to investigating densified nanotube carpets, we also plan to explore composite electrode structures for Li-ion batteries composed of CNT-supported nanoparticle Li-intercalation materials.
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- Figure 1: Carpet of vertically-aligned CNTs grown on a conductive substrate at 475 °C. The catalyst/underlayer system is Fe/Ta. The HRTEM image on the inset shows the crystalline nature of the CNTs (scale bar 5 nm).
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- Figure 2: Vertically aligned CNT carpet transferred to a Au-coated Si substrate via a diffusion-bond transfer, enabling nanotube carpets to be integrated into electrochemical devices.
- Y. G. Guo, J. S. Hu, and L. J. Wan, “Nanostructured materials for electrochemical energy conversion and storage devices,” Advanced Materials, vol. 20, pp. 2878-2887, Aug. 2008. [↩]
- G. D. Nessim, A. J. Hart, J. S. Kim, D. Acquavia, J. Oh, C. D. Morgan, M. Seita, J. S. Leib, and C. V. Thompson, “Tuning of vertically-aligned carbon nanotube diameter and areal density through catalyst pre-treatment,” Nano Letters, vol. 8, pp. 3587-3593, Nov. 2008. [↩]
- G. D. Nessim, M. Seita, K. P. O’Brien, A. J. Hart, R. K. Bonaparte, R. R. Mitchell, and C. V. Thompson, “Low temperature synthesis of vertically aligned carbon nanotubes with electrical contact to metallic substrates enabled by thermal decomposition of the carbon feedstock,” Nano Letters, vol. 9, pp. 3398-3405, Oct. 2009. [↩]
- G. D. Nessim, D. Acquaviva, M. Seita, K. P. O’Brien, and C. V. Thompson, “The critical role of the underlayer material and thickness in grown vertically aligned carbon nanotubes and nanofibers on metallic substrates by chemical vapor deposition,” Adv. Funct. Mat., vol. 20, 2010. [↩]
- B. L. Wardle, D. S. Saito, E. J. Garcia, A. J. Hart, R. G. de Villoria, and V. P. Verploegen, “Fabrication and characterization of ultrahigh-volume-fraction aligned carbon nanotube-polymer composites,” Advanced Materials, vol. 20, pp. 2707-2714, July 2008. [↩]