On the microelectrode behaviour of graphite-epoxy composite electrodes

Electrodes fashioned from conducting particles embedded in insulating binder show some properties commonly associated with arrays of microelectrodes, viz. independence of current from convective flow and sigmoidal current-voltage curves. We have systematically investigated the electrochemical behaviour of a range of composite formulations. The fraction of the surface area that is conducting and the size of the conducting features have been quantified using the novel technique of conducting atomic force microscopy (C-AFM). We have shown that flow sensitivity and voltammetric behaviour are correlated with results from the C-AFM. The more dilute formulations behave like arrays of microelectrodes, though exhibiting large time constants. The origin of this behaviour is discussed.