Double-layer capacity measurements as a method to characterize porous fuel cell electrodes

Growing interest in porous Teflon-bonded carbon and catalyst carbon electrodes has resulted in increasing research efforts to improve performance and lifetime of these electrodes. The impedance method is demonstrated as a useful instrument to investigate these semihydrophobic electrodes. The double-layer capacity, derived by rather simple calculations from impedance spectra, is correlated with important parameters such as Teflon content, fabrication pressure and drying temperature of the electrode as well as to the deterioration processes which are still limiting the lifetime of the electrode. Information needed for improving these electrodes can be deduced from CD measurements. Further interpretation of the impedance spectra and calculation of kinetic data are possible with the aid of appropriate equivalent circuits.