Acceptor-type graphite intercalation compounds

Hoffman, D. M., R. E. Heinz, G. L. Doll, and P. C. Eklund. 1985. Optical reflectance study of the electronic structure of acceptor-type graphite intercalation compounds. Phys. Rev. B 32 1278-1288. 

It forms both types of intercalation compounds, donor (D) and acceptor (A) type. This is quite in contrast to most of the other inorganic host lattice such as, for example, TiSa [31], VaOg, CrgOg, MnOa, C0O2, and many others [29], where D-type compounds, mostly with Li+, are absolutely preferred The reason for this is that graphite is a metal, with a Fermi potential of about —0.2 V vs. SHE (see... 

Metal chloride intercalate compounds such as graphite-FeQa, ZnCl2, BeCl2, ZrCU, NbCls, and TaCls are all Friedel-Crafts catalysts, and their action has been well described. The mechanism of formation of graphite acceptor compounds of this type is of interest in that electrons are removed from graphite to form negative ions the neutral molecules formed at the same time diffuse into the lattice. 

The electronic conductivity of residue compounds is several times higher than that of the parent graphite, but still below the conductivity of either donor- or acceptor-type lamellar compounds. Thus conductivity is a sensitive probe for the reversibility of an intercalation reaction. 

As already mentioned the fundamental condition which must be fulfilled for intercalation to occur is electron transfer from the graphite macromolecule to intercalate or vice versa. This quantity determines directly many physiocochemical properties of GICs. For example, it is obvious that for an acceptor compound the quantity of electrons lost by the graphene layers (some other time understood as the hole concentration), must exactly be compensated by the amount of electrons accumulated in the intercalate layers to assure the electrical balance of the intercalation system. The formation of acceptor and donor-type compounds in the reactions of anodic oxidation and cathodic reduction may be represented by the following equations, respectively,... 

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