A model of the electronic properties of activated carbon

Activated carbon may be regarded as consisting of graphite nanocrystals forming the walls of the pores. These crystallites contain three graphene layers having sizes of 2-4 nm perpendicular to the “c-axis”. A model has been developed of the electronic properties of the material. The model is based on this nano-structure and on experimental results concerning the variation of the conductivity, the thermoelectric power and the ESR signal of activated carbon, immersed in electrolyte solutions, on changing the electrode potential. According to the model, the graphene layers (“domains”) are charged with one, and preferentially two, electrons (or defect electrons) or uncharged, the π-electron system being delocalized throughout a domain. The various types of domains are in thermodynamic equilibria with one another. Charge transport is regarded as transport of charged domains, resembling the “extra” conduction of protons in H-bonding solvents like water, while uncharged domains (like neutral water clusters) do not contribute to the conductivity. Correspondence with electronic energy band models is obtained by constructing electronic levels from the energetic data. Close structural and mechanistic similarities to conducting polymers suggest the applicability of the model also to this material.