Interfacial capacitance and electronic conductance of activated carbon double-layer electrodes

We have measured double-layer capacitance and electronic conductance of an activated carbon electrode in an aprotic electrolyte solution, 1 mol/L (C2H5)(4)NBF4 in acetonitrile. Both quantities show a similar dependence on the electrode potential with distinct minima near the potential of zero charge. This correlation suggests that the capacitance like the conductance is governed substantially by the electronic properties of the solid, rather than by the properties of the solution side of the double layer. These findings can be explained by treating activated carbon as a metal with a finite density of electronic states at the Fermi level, and with hopping conduction between these states. (C) 2003 The Electrochemical Society.