Impedance measurements for determination of pore texture of a carbon membrane

Abstract

The pore texture of a carbon membrane was determined by impedance measurements carried out over a wide frequency range. The impedance obtained could be characterised by a resistance Ω and a double layer capacitance Cn. Ω is the third of electrolyte resistance in pores and Cn is the double layer capacitance corresponding to the developed pore surface. Membrane samples of different length but with the same thickness were studied. As expected, it was shown that the Cn value is proportional to the weight of the membrane whereas the Ω value is inversely proportional. Cn value allowed us to evaluate the specific area of the porous membrane from the value of the double layer capacitance per unit area determined for a plain carbon electrode. Moreover, impedance diagrams obtained were found to be very similar to those of cylindrical pore even though the pore texture is very intricate. Thus, impedance measurements can be applied to porous electrodes of more intricate pore texture and evaluate the radius, depth and pore number of its equivalent cylindrical pore electrode.