Pseudocapacitive properties of electrochemically prepared nickel oxides on 3-dimensional carbon nanotube film substrates

Kyung Wan Nam, Kwang Heon Kim, Eun Sung Lee, Won Sub Yoon, Xiao Qing Yang, Kwang Bum Kim

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Abstract

Nickel oxides on carbon nanotube electrodes (NiOx/CNT electrodes) are prepared by depositing Ni(OH)2 electrochemically onto carbon nanotube (CNT) film substrates with subsequent heating to 300 °C. Compared with the as deposited Ni(OH)2 on CNT film substrates (Ni(OH)2/CNT electrodes), the 300 °C heat treated electrode shows much high rate capability, which makes it suitable as an electrode in supercapacitor applications. X-ray photoelectron spectroscopy shows that the pseudocapacitance of the NiOx/CNT electrodes in a 1 M KOH solution originates from redox reactions of NiOx/NiOxOH and Ni(OH)2/NiOOH. The 8.9 wt.% NiOx in the NiOx/CNT electrode shows a NiOx-normalized specific capacitance of 1701 F g-1 with excellent high rate capability due to the 3-dimensional nanoporous network structure with an extremely thin NiOx layer on the CNT film substrate. On the other hand, the 36.6 wt.% NiOx/CNT electrode has a maximum geometric and volumetric capacitance of 127 mF cm-2 and 254 F cc-1, respectively, with a specific capacitance of 671 F g-1, which is much lower than that of the 8.9% NiOx electrode. This decrease in specific capacitance of the high wt.% NiOx/CNT electrodes can be attributed to the dead volume of the oxides, high equivalent series resistance for a heavier deposit, and the ineffective ionic transportation caused by the destruction of the 3-dimensional network structure. Deconvolution analysis of the cyclic voltammograms reveals that the rate capability of the NiOx/CNT electrodes is adversely affected by the redox reaction of Ni(OH)2, while the adverse effects from the reaction of NiOx is insignificant.

Original languageEnglish
Pages (from-to)642-652
Number of pages11
JournalJournal of Power Sources
Volume182
Issue number2
DOIs
Publication statusPublished - 2008 Aug 1

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All Science Journal Classification (ASJC) codes

  • Renewable Energy, Sustainability and the Environment
  • Energy Engineering and Power Technology
  • Physical and Theoretical Chemistry
  • Electrical and Electronic Engineering

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