TY - JOUR
T1 - QM/MD simulation of SWNT nucleation on transition-metal carbide nanoparticles
AU - Page, Alister J.
AU - Yamane, Honami
AU - Ohta, Yasuhito
AU - Irle, Stephan
AU - Morokuma, Keiji
PY - 2010/11/10
Y1 - 2010/11/10
N2 - The mechanism and kinetics of single-walled carbon nanotube (SWNT) nucleation from Fe- and Ni-carbide nanoparticle precursors have been investigated using quantum chemical molecular dynamics (QM/MD) methods. The dependence of the nucleation mechanism and its kinetics on environmental factors, including temperature and metal-carbide carbon concentration, has also been elucidated. It was observed that SWNT nucleation occurred via three distinct stages, viz. the precipitation of the carbon from the metal-carbide, the formation of a "surface/subsurface"carbide intermediate species, and finally the formation of a nascent sp2-hybidrized carbon structure supported by the metal catalyst. The SWNT cap nucleation mechanism itself was unaffected by carbon concentration and/or temperature. However, the kinetics of SWNT nucleation exhibited distinct dependences on these same factors. In particular, SWNT nucleation from NixCy nanoparticles proceeded more favorably compared to nucleation from Fe xCy nanoparticles. Although SWNT nucleation from Fe xCy and NixCy nanoparticle precursors occurred via an identical route, the ultimate outcomes of these processes also differed substantially. Explicitly, the Nix-supported sp2-hybridized carbon structures tended to encapsulate the catalyst particle itself, whereas the Fex-supported structures tended to form isolated SWNT cap structures on the catalyst surface. These differences in SWNT nucleation kinetics were attributed directly to the relative strengths of the metal-carbon interaction, which also dictates the precipitation of carbon from the nanoparticle bulk and the longevity of the resultant surface/subsurface carbide species. The stability of the surface/subsurface carbide was also influenced by the phase of the nanoparticle itself. The observations agree well with experimentally available data for SWNT growth on iron and nickel catalyst particles.
AB - The mechanism and kinetics of single-walled carbon nanotube (SWNT) nucleation from Fe- and Ni-carbide nanoparticle precursors have been investigated using quantum chemical molecular dynamics (QM/MD) methods. The dependence of the nucleation mechanism and its kinetics on environmental factors, including temperature and metal-carbide carbon concentration, has also been elucidated. It was observed that SWNT nucleation occurred via three distinct stages, viz. the precipitation of the carbon from the metal-carbide, the formation of a "surface/subsurface"carbide intermediate species, and finally the formation of a nascent sp2-hybidrized carbon structure supported by the metal catalyst. The SWNT cap nucleation mechanism itself was unaffected by carbon concentration and/or temperature. However, the kinetics of SWNT nucleation exhibited distinct dependences on these same factors. In particular, SWNT nucleation from NixCy nanoparticles proceeded more favorably compared to nucleation from Fe xCy nanoparticles. Although SWNT nucleation from Fe xCy and NixCy nanoparticle precursors occurred via an identical route, the ultimate outcomes of these processes also differed substantially. Explicitly, the Nix-supported sp2-hybridized carbon structures tended to encapsulate the catalyst particle itself, whereas the Fex-supported structures tended to form isolated SWNT cap structures on the catalyst surface. These differences in SWNT nucleation kinetics were attributed directly to the relative strengths of the metal-carbon interaction, which also dictates the precipitation of carbon from the nanoparticle bulk and the longevity of the resultant surface/subsurface carbide species. The stability of the surface/subsurface carbide was also influenced by the phase of the nanoparticle itself. The observations agree well with experimentally available data for SWNT growth on iron and nickel catalyst particles.
UR - http://www.scopus.com/inward/record.url?scp=78649731279&partnerID=8YFLogxK
U2 - 10.1021/ja106264q
DO - 10.1021/ja106264q
M3 - Article
AN - SCOPUS:78649731279
SN - 0002-7863
VL - 132
SP - 15699
EP - 15707
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 44
ER -