Spectroscopic study of X-ray absorption near-edge structure of chemical states of Pt catalyst during growth of single-walled carbon nanotubes

Growth of single-walled carbon nanotubes (SWCNTs) by alcohol catalytic chemical vapor deposition with the assistance of Pt as a catalyst is a useful technique because small-diameter SWCNTs are prepared under low ethanol pressure. In the study reported here, we carried out spectroscopy of X-ray absorption near-edge structure (XANES) to investigate the chemical bonding states of the Pt catalyst during SWCNT growth. Pt L3-edge XANES spectra of the Pt catalyst showed that it was reduced during pre-heating and remained metallic during SWCNT growth. This indicates that carbon atoms dissociated from the ethanol molecules did not dissolve into the Pt catalyst particles, but diffused on their surface and formed SWCNTs. Based on the XANES results, a model of Pt-catalyzed SWCNT growth is proposed.