Change of electrochemical impedance spectra (EIS) with time during CO-poisoning of the Pt-anode in a membrane fuel cell

摘要

The most common method used to characterize the electrochemical performance of a fuel cell is the recording of current/voltage U(i) curves. However, separation of electrochemical and ohmic contributions to the U(i) characteristics requires additional experimental techniques. The application of electrochemical impedance spectroscopy （EIS) is an approach to determine, which have proved to be indispensable for the development of fuel cell electrodes and membrane electrode assemblies (MEA's). The impedance spectra measured during CO poisoning of the anode in galvanostatic mode at 217 mAcm{sup}(-2)show a strong time dependency. From the evaluation of the spectra with an equivalent circuit we suggest that the hydrogen dissociation reaction is the reaction rate determining step. At lower cell voltages the CO oxidation reaction occurs and the Faraday impedance of the anode shows an inductive response at frequencies lower than 3 Hz.