Graphene processability

When the electrolyte solutions are not too reactive, as in the case of ethereal solutions, there is no massive formation of protective surface films at potentials above Li intercalation potential, and most of the solvent reduction processes may occur at potentials lower than 0.3 V vs. Li/Li+. Hence, the passivation of the electrodes is not sufficient to prevent cointercalation of solvent molecules. This leads to an exfoliation of the graphite particles into amorphous dust (expholiated graphene planes). This scenario is demonstrated in Figure 2a as the reduction of the 002 diffraction peak21 of the graphite electrode, polarized cathodically in an ethereal solution. 

One synthesis approach that does not rely on CNT formation from the gas phase is molten salt synthesis. The reactor consists of a vertically oriented quartz tube that contains two graphite electrodes (i.e. anode is also the crucible) and is filled with ionic salts (e.g. LiCl or LiBr). An external furnace keeps the temperature at around 600 °C, which leads to the melting of the salt. Upon applying an electric field the ions penetrate and exfoliate the graphite cathode, producing graphene-type sheets that wrap up into CNTs on the cathode surface. Subsequently, the reactor is allowed to cool down, washed with water, and nanocarbon materials are extracted with toluene [83]. This process typically yields 20-30 % MWCNTs of low purity. 

H. Kim, C.W. Macosko, Processing-property relationships of polycarbonate/graphene composites, Polymer, 50 (2009) 3797-3809. 

H.A. Becerril, J. Mao, Z. Liu, R.M. Stoitenberg, Z. Bao, Y. Chen, Evaluation of solution-processed reduced graphene oxide films as transparent conductors, ACS Nano, 2 (2008)... 

Y. F. Huang, C. W. Lin, Facile synthesis and morphology control of graphene oxide/polyaniline nanocomposites via in-situ polymerization process, Polymer, vol. 53, pp. 2574-2582, 2012. 

Fig. 5.14 (a) Schematic of SEED process of metal NP deposition on metai surface supported nanoparticie. (b) Example of Au NP deposition on CVD grown graphene on Cu foil, scale 1pm. Reproduced with permission from [143], (2012) Elsevier. 

Fan, G.-Q., et ah, Plasmonic-enhanced polymer solar cells incorporating solution-processable Au nanoparticle-adhered graphene oxide. Journal of Materials Chemistry, 2012. 22(31) ... 

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