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Impedances of a gold-powder and a Raney-gold electrode were measured over a wide frequency range, and were found to be very similar to those of cylindrical pore of finite depth. The simulation calculation for sphere-packed electrode impedance was performed. It was observed that even though each sphere-layer shows the impedance related to an occluded pore-shape, the overall impedance is similar to that of a cylindrical pore electrode. When the penetration depth approaches the pore depth, the shape of the pore wall has little influence on the impedance. Thus, impedance measurement techniques 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. These values determined for a Raney-gold electrode are in very good agreement with those determined by other methods. The case of a more realistic fuel cell electrode such as Raney-nickel with a metal-electrolyte-gas system, was also tentatively examined.

The pore texture of Raney-nickel was determined by impedance measurements carried out over a wide frequency range. The impedance obtained could be characterized by three resistances, R, Re and Rt and one capacitor C. R is the high frequency limit of the electrode impedance, and is equal to the electrolyte resistance between the reference capillary-tip and the upper-surface of catalyst layer. Re is the electrolyte resistance through the cavity of catalyst layer. Rt is linked in parallel with the capacitor C.C value allows to evaluate the surface area of catalyst in contact with electrolyte provided that the double layer capacitance of nickel electrode per unit surface is known. R value, measured with and without catalyst layer allows to estimate its thickness, hence the total pore volume when the density of catalyst-metal is known. The Raney-nickel has a double pore-structure: the one related to micro-pores inside catalyst grain and the other to a heaping of grains. If the volumes of these two types of pore are known, the pore radius of micro-pore can be evaluated. Therefore, impedance measurements determine, in situ, the pore texture of Raney-nickel in liquid phase. Results were in good agreement with those determined in gas phase by current methods.