Disentangling Vacancy Oxidation on Metallicity-Sorted Carbon Nanotubes

Duncan J. Mowbray, Alejandro Pérez Paz, Georgina Ruiz-Soria, Markus Sauer, Paolo Lacovig, Matteo Dalmiglio, Silvano Lizzit, Kazuhiro Yanagi, Andrea Goldoni, Thomas Pichler, Paola Ayala, Angel Rubio

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

Pristine single-walled carbon nanotubes (SWCNTs) are rather inert to O2 and N2, which for low doses chemisorb only on defect sites or vacancies of the SWCNTs at the ppm level. However, very low doping has a major effect on the electronic properties and conductivity of the SWCNTs. Already at low O2 doses (80 L), the X-ray photoelectron spectroscopy (XPS) O 1s signal becomes saturated, indicating nearly all of the SWCNT's vacancies have been oxidized. As a result, probing vacancy oxidation on SWCNTs via XPS yields spectra with rather low signal-to-noise ratios, even for metallicity-sorted SWCNTs. We show that, even under these conditions, the first-principles density functional theory calculated Kohn-Sham O 1s binding energies may be used to assign the XPS O 1s spectra for oxidized vacancies on SWCNTs into its individual components. This allows one to determine the specific functional groups or bonding environments measured. We find the XPS O 1s signal is mostly due to three O-containing functional groups on SWCNT vacancies: epoxy (C2>O), carbonyl (C2>C=O), and ketene (C=C=O), as ordered by abundance. Upon oxidation of nearly all of the SWCNT's vacancies, the central peak's intensity for the metallic SWCNT sample is 60% greater than that for the semiconducting SWCNT sample. This suggests a greater abundance of O-containing defect structures on the metallic SWCNT sample. For both metallic and semiconducting SWCNTs, we find O2 does not contribute to the measured XPS O 1s spectra.

Original languageEnglish
Pages (from-to)18316-18322
Number of pages7
JournalJournal of Physical Chemistry C
Volume120
Issue number32
DOIs
Publication statusPublished - Aug 18 2016
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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