Electrochemical Impedance Spectroscopy as a Diagnostic Tool for High-Temperature PEM Fuel Cells

Abstract

Electrochemical Impedance Spectroscopy (EIS) is used to investigate the impact of acid doping level, air stoichiometry, polymer membrane type, and catalyst material on the operation of Membrane Electrode Assemblies (MEA) for high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). EIS spectra are recorded during operation and analyzed by means of an equivalent circuit model to separate the contributions of individual internal losses. Acid doping level in membrane and electrodes plays a major role for MEA performance. Air stoichiometry influences the MEA operation mainly by affecting the cathode mass transport and charge transfer losses. The investigated membrane materials have little effect on MEA performance, although differences are observed in the shapes of the EIS spectra. The use of a Pt3Co/C alloy catalyst improves the MEA performance to a record value of 707 mV at 200 mA cm-2 in the polarization curve.