Graphene edge atoms

We have also carried out some initial calculations on BN substituted graphene nanoribbons with passivated edge atoms. We find that the edge atoms have finite magnetic moments, more so if the edge atoms are B and N. In fact, due to the finite magnetic moments at the edge sites, the delocalization of... 

DFT calculations have also demonstrated that in addition to the enhanced capacity to oxidize C atoms and CH fragments, the Sn/Ni surface alloy also lowers the thermodynamic driving force associated with the formation of carbon nucleation centers at low-coordinated Ni sites [16], DFT calculated adsorption energies for various carbon nucleation centers (a carbon atom, a cluster of 8 carbon atoms, and a graphene chain) on monometallic Ni and Sn/Ni surface alloy are shown in Fig. 13.4. The figure shows that for all carbon stractures, the under-coordinated sites on Ni (to model these sites, the Ni(211) surface was used) bind carbon more strongly than the under-coordinated sites on Sn/Ni(211) (in this model systan 1/3 of Ni edge atoms were displaced by Sn atoms). The reason for this is that Sn atoms break the ensembles of... 

The reason for this factor of about 60 in ORR activity between the two types of N-doped carbon catalysts, i.e., N-doped carbons made with strategic metals like Fe or Co and those made without any strategic metal, is what divides the scientific community. One camp believes the presence of Fe-Nx or Co-Nx catalytic sites explains the drastic improvement while the other defends the hypothesis that a larger number of N atoms (pyridinic or graphitic) or a larger number of graphene edges catalyzed by Fe or Co is what explains the difference. 

Figure 5.16. Positions of Fe atoms on the edge of nifrogenated graphene (i) Fe bond sites a, b, c (ii) models of nitrided graphene edge being passivated by hydrogen atoms and bonded with Fe. Here Fe is coordinated with three NH3 ligands [95]. (Reprinted with permission from J Phys Chem B 2006 110(9) 4179-85. Copyright 2006 American Chemical Society.)...

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