Microstructure and Pseudocapacitive Properties of Electrodes Constructed of Oriented NiO-TiO2 Nanotube Arrays

Jae Hun Kim, Kai Zhu, Yanfa Yan, Craig L. Perkins, Arthur J. Frank

Research output: Contribution to journalArticlepeer-review

422 Scopus Citations

Abstract

We report on the synthesis and electrochemical properties of oriented NiO-TiO2 nanotube (NT) arrays as electrodes for supercapacitors. The morphology of the films prepared by electrochemically anodizing Ni-Ti alloy foils was characterized by scanning and transmission electron microscopies, X-ray diffraction, and photoelectron spectroscopies. The morphology, crystal structure, and composition of the NT films were found to depend on the preparation conditions (anodization voltage and postgrowth annealing temperature). Annealing the as-grown NT arrays to a temperature of 600 °C transformed them from an amorphous phase to a mixture of crystalline rock salt NiO and rutile TiO2. Changes in the morphology and crystal structure strongly influenced the electrochemical properties of the NT electrodes. Electrodes composed of NT films annealed at 600 °C displayed pseudocapacitor (redox-capacitor) behavior, including rapid charge/discharge kinetics and stable long-term cycling performance. At similar film thicknesses and surface areas, the NT-based electrodes showed a higher rate capability than the randomly packed nanoparticle-based electrodes. Even at the highest scan rate (500 mV/s), the capacitance of the NT electrodes was not much smaller (within 12%) than the capacitance measured at the slowest scan rate (5 mV/s). The faster charge/discharge kinetics of NT electrodes at high scan rates is attributed to the more ordered NT film architecture, which is expected to facilitate electron and ion transport during the charge-discharge reactions.

Original languageAmerican English
Pages (from-to)4099-4104
Number of pages6
JournalNano Letters
Volume10
Issue number10
DOIs
StatePublished - 2010

NREL Publication Number

  • NREL/JA-590-49356

Keywords

  • anodization
  • nanotube
  • nickel oxide
  • Supercapacitor

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