Investigation of Modell Electrodes with Different Catalysts and Ionomer Content of Polymer Fuel Cells by Electrochemical Impedance Spectroscopy

Abstract

To increase the performance and the long term stability of Membrane Electrode Assemblies (MEA) it is necessary to investigate the electrode structure. Therefore model electrodes with different type of catalysts with varying amount of ionomer where prepared and characterized. As electrode materials, supported and unsupported platinum catalysts and as ionomer Nafion in powder form were used. The electrodes were applied on both sides of Nafion 1135 membranes. The most common method to characterize the electrochemical performance of a fuel cell is recording of current/voltage U(i) curves. However, separation of electrochemical and ohmic contributions to the U(i) characteristics requires additional experimental techniques. In this regard electrochemical impedance spectra were measured in addition to U(i) curves to characterize the different model electrodes.