II International Symposium on Carbon for Catalysis ABSTRACTS

PP-I-50
DENSITY FUNCTIONAL CALCULATIONS ON THE FORMATION OF CARBON
NANOFIBERS
Zhu Y., Dai Y., Zhou J., Sui Zh., Yuan W.
State Key Laboratory of Chemical Reaction Engineering, East China University of Science
and Technology, Shanghai 200237, China
e-mail: yanzhu@ecust.edu.cn
Introduction
Carbon nanofiber (CNF) is attracting increased attention. There are two major reasons for
studying this particular kind of carbon. On the one hand, filamentous carbon is formed in a
temperature range where reactions of great technical importance, e.g., Fisher-Tropsch
synthesis, methanation, and steam-reforming, are usually carried out. On the other hand,
because of the unique chemical and physical properties induced by the CNF geometric and
electronic structure, CNF has been applied in many fields such as catalysts, catalyst supports,
gas storage materials, electrodes for fuel cell, and polymer additives. CNFs are synthesized
mainly by chemical vapor deposition (CVD). The global evolution of the growth is divided
into three stages: firstly, carbon atoms and hydrogen molecules are formed with the
decomposition of carbon-containing gas on certain transition metal surface; secondly, the
generated carbon atoms dissolve into the metal particle and diffuse through the bulk or along
the surface; finally, the carbon atoms precipitate in the form of graphene layer on the rear side
of the metal particle. The second stage is generally regarded as the rate-determining step
because the activation energy for carbon diffusion is in reasonable agreement with that for the
CNF formation in a range of 1.3-1.5eV. However, in fact, the CNF growth mechanism at the
atomic scale is still unclear.
As suggested microdiffraction data, the [100] crystallographic direction of the FCC Ni lattice
coincided with the filament axis, and (111) planes which were parallel to the graphite sheet
accounted for the nucleation of the filament. This point was also confirmed by Yang and
Chen who performed both experimental and theoretical studies on carbon filament growth,
and verified that the Ni(100) and Ni(110) were among the gas/metal interface, while the
Ni(111) and Ni(311) were among the graphite/metal interface. In this paper, the diffusion of
carbon atoms on Ni(111) is focused.
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