Highly selective growth of vertically aligned double-walled carbon nanotubes by a controlled heating method and their electric double-layer capacitor properties

Vertically aligned double‐walled carbon nanotubes (DWCNTs) with the highest selectivity of 90% were synthesized by a controlled heating method and their electric double‐layer capacitor characteristics were evaluated. DWCNT arrays had a specific capacitance of 83 F/g, which is one of the highest values among CNT arrays in a nonaqueous solution and is almost equivalent to that for single‐walled CNT (SWCNT) arrays reported previously. At the same specific capacitance, DWCNTs with superior structural properties are more promising for practical capacitors than SWCNTs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) The authors report the growth and EDLC properties of vertically aligned DWCNTs with a high selectivity of 90%. The catalyst particle size appropriate for DWCNT growth was obtained by a precise control of the preheating temperature for particle formation. DWCNT arrays showed a high specific capacitance. Since DWCNTs have superior structural properties to SWCNTs, they are more promising materials for practical capacitors.