title: Quantum Chemical Simulation of Carbon Nanotube Nucleation on Al2O3 Catalysts via CH4 Chemical Vapor Deposition.
abstract: We present quantum chemical simulations demonstrating how single-walled carbon nanotubes (SWCNTs) form, or "nucleate", on the surface of Al2O3 nanoparticles during chemical vapor deposition (CVD) using CH4. SWCNT nucleation proceeds via the formation of extended polyyne chains that only interact with the catalyst surface at one or both ends. Consequently, SWCNT nucleation is not a surface-mediated process. We demonstrate that this unusual nucleation sequence is due to two factors. First, the π interaction between graphitic carbon and Al2O3 is extremely weak, such that graphitic carbon is expected to desorb at typical CVD temperatures. Second, hydrogen present at the catalyst surface actively passivates dangling carbon bonds, preventing a surface-mediated nucleation mechanism. The simulations reveal hydrogen's reactive chemical pathways during SWCNT nucleation and that the manner in which SWCNTs form on Al2O3 is fundamentally different from that observed using "traditional" transition metal catalysts.
authors.affiliation: †Newcastle Institute for Energy and Resources, The University of Newcastle, Callaghan 2308, Australia.
authors.forename: Alister J
authors.initials: AJ
authors.lastname: Page
authors.affiliation: †Newcastle Institute for Energy and Resources, The University of Newcastle, Callaghan 2308, Australia.
authors.forename: Supriya
authors.initials: S
authors.lastname: Saha
authors.affiliation: §School of Ocean, Shandong University, Weihai 264209, China.
authors.forename: Hai-Bei
authors.initials: HB
authors.lastname: Li
authors.affiliation: ∥Institute of Transformative Bio-Molecules (WPI-ITbM) and Department of Chemistry, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan.
authors.forename: Stephan
authors.initials: S
authors.lastname: Irle
authors.affiliation: ‡Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Morokuma
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry*; D002384:Catalysis; D006859:Hydrogen / Q000737:chemistry; D008697:Methane / Q000737:chemistry*; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D053758:Nanoparticles / Q000737:chemistry; D037742:Nanotubes, Carbon / Q000737:chemistry*; D011789:Quantum Theory; D012825:Silicon / Q000737:chemistry; D014835:Volatilization
chemical_list: D037742:Nanotubes, Carbon; D006859:Hydrogen; D000537:Aluminum Oxide; D008697:Methane; D012825:Silicon