Glassy carbon electrodes double-layer capacitance

Capacitance measurements of carbon electrodes have also been made in molten halides, particularly chlorides [30-32], molten nitrates [33, 34], and in cryolite—alumina melts (graphite and glassy carbons). In cryolite—alumina melts, the double-layer capacitance of the basal plane of graphite, in the range 0.7—1.0 V (vs aluminum reference electrode) is about 20[xF/cm at 0.9 V, i.e., in a potential range where no appreciable flow of current has been observed. Data indicate that the capacitance is influenced by adsorbed species from the melt, possibly yielding intercalation compounds, and uncertainty in the true area of the electrode [34]. 

RALEIGH Some of your double layer capacitance data, such as for silver halides on glassy carbon, seem too low (tenths of yF/cm ) for a 1 st-ions-layer capacitance. I would suggest that one way one can get a voItage-independent para1le1-plate-type capacitance is by an impurity layer, say of oxygen or nitrogen molecules between the electrode and electrolyte and that this is a possibility that is always difficult to rule out. 

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