Surface chemistry edge planes

Figure 5.4 summarizes in a schematic way the current state of knowledge of carbon surface chemistry, with an emphasis on the details of graphene edges. As discussed in Section 5.2.1, it shows the dominant surface functionalities, all containing oxygen because of the often inevitable contact of realistic carbon materials with 02 from air. The main features of interest here are (i) the existence of free edge sites and (ii) the notion that the basal plane is not as chemically inert as is often... 

Fig. 11.22. Example structures for monolayer covalent bonding to edge plane pyrolytic graphite electrodes. (Reprinted from Techniques of Chemistry, Molecular Design of Electrode Surfaces, R. W. Murray, ed., Vol. 22, p. 143. Copyright 1992 John Wiley Sons. Reprinted by permission of John Wiley Sons, Inc.)...

It is now generally accepted that the surface chemistry and morphology of the edge planes of graphite play a major role in the chemical and electrochemical reactivity of this material in contact with electrolyte. In order to determine whether there is a correlation between the composition and morphology of the SEI formed on the HOPG and on the real anode in lithium-ion batteries, we... 

For carbon anodes, the exchange-current density of the reduction reactions also depends on the surface properties of the electrode (content of impurities, surface chemistry and surface morphology). The SEI functions differently on the basal and on the cross-section planes. Consequently, the surface chemistry and morphology of the SEI vary with the basal-plane to edge-plane area ratio of carbon. We suggest that the carbon matrix has a more marked effect on the composition and thickness of the SEI than does the nature of the electrolyte. 

Fig. 4.9 AFM images of the as received commercially available CVD graphene surface, observed from various top-down (a) and three-dimensional (b) perspectives. Note that the surface is generally akin to that of a HOPG surface, but is highly disordered and thus as a result there is a high edge plane content making, the two electrodes in comparison act electrochemically similar. Reproduced from Ref. [31] with permission from The Royal Society of Chemistry...

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