Alterations in the local structure of the Co/SiO 2 dispersed carbon nanotubes induced by CO molecules during microwave irradiation
Journal
Materials Chemistry and Physics
Journal Volume
135
Journal Issue
2-3
Pages
438-444
Date Issued
2012
Author(s)
Abstract
This study presents a detailed structural investigation of Co/SiO 2 catalysts dispersed carbon nanotubes (CNTs) treated by microwave in Ar and CO ambient, using X-ray absorption spectroscopy and Raman scattering. For the local structure of the cobalt site in the Co/SiO 2 catalysts dispersed CNTs treated by microwave in Ar, the coordination number (N Co-Co) of the first shell is 10.8 with a Co-Co bond length of 2.496 Å, corresponding to the Co-Co bonding in cubic cobalt metal. After the microware treatment in CO, partial amounts of the cobalt species in the Co/SiO 2 catalysts are translated to Co 2+. In terms of the local structure of carbon site, the π orbital in CNTs are more delocalized than those in graphite and the defects are significant in the case of treating by microwave in Ar. For the microwave treatment in CO, the C-C π* transition energy shifts to that of graphite and the C-C σ* increases, indicating that the defect density is reduced by the microwave treatment in CO ambient. This detailed knowledge of the local structural translation is useful to the modification of the structure of CNTs. © 2012 Elsevier B.V. All rights reserved.
SDGs
Type
journal article