Evidence for Vertical C2 on Ni as a Precursor for Graphite Nucleation
GEORGE WASHINGTON UNIV WASHINGTON DC DEPT OF CHEMISTRY
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We interpret previously published C K edge CEELS and NEXAFS data for carbon Ni between 500-700K. The C K CEELS data for CONi at 500K reveal the presence of C-C bonding on the surface, i.e. horizontal Cnn2,3... The CEELS data for carbon at 620K reveal that some of the C2 species flip up at this temperature, while the others dissociate. Evidence for vertical C2 is seen only at higher carbon coverages suggesting that some of the C2 are forced to flip up to make room for neighboring horizontal C2s to dissociate. These vertical C2s then apparently serve as the precursor for the nucleation of graphite, as it explains the lack of graphite formation at lower coverages when total dissolution into the bulk occurs.
- Atomic and Molecular Physics and Spectroscopy