Relationship between carbon nanotube structure and electrochemical behavior: heterogeneous electron transfer at electrochemically activated carbon nanotubes.
The electrochemical activation of multiwalled carbon nanotubes (MWCNTs) (at potentials of 1.5-2.0 V vs Ag/AgCl for 60-360 s) results in significantly increased rate constants (k(0)((obs))) for heterogeneous electron-transfer with [Fe(CN)(6)](3-/4-) (from 8.34 x 10(-5) cm s(-1) for as-received MWCNTs to 3.67 x 10(-3) cm s(-1) for MWCNTs that were electrochemically activated at 2.0 V for 180 s). The increase in the value of k(0)((obs)) arises from the introduction of wall defects exposing edge planes of the MWCNTs, as observed by high-resolution TEM. The density of the edge plane defects increases from almost zero (for as-received MWCNTs) to 3.7 % (for MWCNTs electrochemically activated at 2.0 V for 180 s). High-resolution X-ray photoelectron spectroscopy (HR-XPS), Raman spectroscopy, and electrochemical impedance spectroscopy were used to gain a better understanding of the phenomena. HR-XPS revealed that the increase in electrochemical activation potential increases the number of oxygen-containing groups on the surface of carbon nanotubes.
Pumera
Martin
M
Biomaterial Systems Group, Biomaterials Center and International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Nanomaterials & Biomaterials Research Building, Tsukuba, Ibaraki (Japan). PUMERA.Martin@nims.go.jp
Sasaki
Toshio
T
Iwai
Hideo
H
D004563:Electrochemistry; D004579:Electron Transport; D007700:Kinetics; D046529:Microscopy, Electron, Transmission; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000648:ultrastructure; D013059:Spectrum Analysis, Raman
D037742:Nanotubes, Carbon