Graphene structure

Figure 1. Schematic description of a (lithium ion) rocking-chair cell that employs graphitic carbon as anode and transition metal oxide as cathode. The undergoing electrochemical process is lithium ion deintercalation from the graphene structure of the anode and simultaneous intercalation into the layered structure of the metal oxide cathode. For the cell, this process is discharge, since the reaction is spontaneous.

Figure 17. Schematic drawing of the GlC-exfoliation model. Differentiation of the stereo difference among EC, PC, and related carbonates by graphene structure.

The extent of the irreversible capacity depends on both the anode material and the electrolyte composition. Empirical knowledge indicates that the PC presence, which is well-known for its tendency to cause the exfoliation of the graphene structures, is especially apt to induce such irreversible capacities. On the other hand, reformulation of the electrolyte may lead to significant reduction in the irreversible capacity for given electrode materials. 

Unfortunately, TMP was found to be cathodically unstable on a graphitic anode surface, where, in a manner very similar to PC, it cointercalated into the graphene structure at 1.20 V and then decomposed to exfoliate the latter, although its anodic stability did not seem to be a problem. Eor this reason, TMP has to be used in amounts less than 10% with EC and other carbonates in high concentration in order to achieve decent performance in lithium ion cells. However, capacity fading caused by the increase of cell impedance cast doubt on the application of this flame retardant in a lithium ion cell. To avoid the poor cathodic stability of TMP on graphitic anodes, the possibility of using it with other amorphous carbon electrodes was also explored by the authors. ... 

Yan JA, Chou MY (2010) Oxidation functional groups on graphene structural and electronic properties. Phys Rev B 82 125403... 

Figure 2. The columnar structure as seen in TEM cross section of a C-Ni nanocomposite film (left). The HREM images (centre and right) show the graphene structure of the carbon matrix between the Ni3C grains near the bottom and the top of the film, respectively.

Under suitable conditions, the reaction of perfluorinated hydrocarbons like teflon (PTFE) or perfluoronaphthalene with alkali amalgam yields carbon nanostructures as weU. The reductive dehalogenation generates intermediate polyynes that subsequently condense to give the respective graphene structures. Normally, a rruxture of carbon nanotubes and onions is obtained. 

Geim, A. K., and K. S. Novoselov. The Rise of Graphene. Nature Materials 6 (March 2007) 183. This article describes graphenes structure, manufacture, and potential in an entirely new class of two-dimensional materials. 

Carbon nanotubes synthesized by the catalytic route exhibit a less well-defined graphene structure compared to those formed by the arc-discharge method due to the low synthesis temperature. This can be rectified by submitting these nanotubes to a high temperature treatment in the range of 1800 to 2600 °C under an inert atmosphere. The heat-treated carbon nanotubes exhibit a more ordered graphene structure compared to their counterpart obtained after the low-temperature synthesis via catalytic route (Fig. 7.10A and B). 

Prepare a sheet showing an extended graphene structure, approximately 12 by 15 fused carbon rings or larger. Use this sheet to show how the graphene structure could be rolled up to form (a) a zigzag nanotube, (b) an armchair nanotube, and (c) a chiral nanotube. Is more than one chiral structure possible (See M. S. Dresselhaus, G. Dresselhaus, and R. Saito, Carbon, 1995, 33, 883.)... 

Inspired by the observation, that binary Pt=Ru nanoparticles supported on CNT showed a promising performance as anode catalysts in PEMFCs, Harris et al. [65] used density functional theory calculations to study the anchoring of the nanoparticles to the nanofibers. They found a strong metal-carbon bond ( 3 eV) with covalent character between the graphene structure and the metal (111) crystal planes, which might be the reason for the higher stability found in these systems. 

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