Applications of carbon nanotubes to hydrogen storage, supercapacitors, amplifiers, and field emission displays

Young Hee Lee

Department of physics, Sungkyunkwan University, Suwon, Kyunggi 440-746, South Korea

Abstract

Carbon nanotubes have been intensively investigated for their fundamental and technical importances. Structural diversities and the related diverse physical properties with large aspect ratio and small diameter and hollowness are fascinating. For instance, carbon nanotubes are metal and semiconductors depending on its chirality and furthermore the band gap can be tailored by the diamters. Several issues for the applications to energy storage of hydrogen storage, secondary battery, supercapacitors and electronic devices of amplifiers of secondary electron emission and field emission displays will be discussed. Energy storage using hydrostatic pressure and electrochemical approaches with carbon nanotubes are currently on debate. The maximum storage capacity reported so far varies from group to group. We will demonstrate that the storage capacity is strongly dependent on the sample-preparation conditions. The stability, flatness on the voltage scan, and cycle life will be extensively discussed. On the other hand, the supercapacitor with non-fadadaic reaction has long cycle life and high power density but low energy density. Therefore development of a supercapacitor with high energy density is always desirable. We demonstrated already a maximum capacitance of 180 F/g and a measured power density of 20 KW/kg and an energy density of 7 Wh/kg in a solution of 7.5 N KOH using singlewalled carbon nanotubes[1]. These values are still lower than that of commercially available activated carbons. We will report our effort to improve the energy density using various nanotube-polymer composites.

Applications to the secondary electron emission and field emission displays are technologically important. By depositing secondary electron materials on vertically aligned multiwalled carbon nanotubes, we were able to obtain unmeasurably high amplification factor. This anomalous behavior of the amplification factor will be explained in terms of avalanche effect. Our CVD synthesis to prepare aligned nanotube films at temperature below the glass melting temperatures for field emission displays will be extensively discussed and the corresponding emission characteristics for for various gas adsorbates and tip morphologies will also be discussed.

Keywords: two-step purification processes, singlewalled carbon nanotubes, multiwalled carbon nanotubes .

[1] K. H. An, W. S. Kim, Y. S. Park, S. M. Lee, S. C. Lim, D. J. Bae, Y. H. Lee, Advanced Materials, 2001, in press.

Corresponding author : Young Hee Lee

e-mail : leeyh@sprc2.chonbuk.ac.kr

Fax: +82-63-270-3585

Tel: +82-63-270-3336