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Relationship between Carbon Nanotube Structure and Electrochemical Behavior: Heterogeneous Electron Transfer at Electrochemically Activated Carbon Nanotubes
Author(s) -
Pumera Martin,
Sasaki Toshio,
Iwai Hideo
Publication year - 2008
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.200800218
Subject(s) - x ray photoelectron spectroscopy , carbon nanotube , raman spectroscopy , materials science , dielectric spectroscopy , electrochemistry , electron transfer , analytical chemistry (journal) , chemical engineering , nanotechnology , chemistry , electrode , organic chemistry , physics , optics , engineering
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 ( ${k_{{\rm{obs}}}^0 }$ ) for heterogeneous electron‐transfer with [Fe(CN) 6 ] 3−/4− (from 8.34×10 −5 cm s −1 for as‐received MWCNTs to 3.67×10 −3 cm s −1 for MWCNTs that were electrochemically activated at 2.0 V for 180 s). The increase in the value of ${k_{{\rm{obs}}}^0 }$ 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.