Spatially resolved electrochemical characterization of a PEM fuel cell stack during durability testing

The durability of proton exchange membrane fuel cells (PEMFC) is a decisive factor for their use in heavy-duty applications. In order to increase durability, it is important to identify and understand the aging mechanisms. In large-area PEMFCs, inhomogeneities occur across the active area right from beginning of life, which have a decisive influence on degradation. This paper presents results on aging phenomena with a particular focus on spatially resolved degradation. A heavy-duty relevant load cycle was applied for more than 2000 h to a PEMFC stack with an active area of 280 cm 2 . At regular intervals, detailed electrochemical characterizations such as polarization curves, sensitivity tests, and electrochemical impedance spectroscopy at cell level and spatially resolved were performed. Degradation impact increases with decreasing pressure, especially in the resistance of the oxygen reduction reaction. Mass transport losses are primarily affected in the cathode outlet area and show the greatest dependence on stoichiometry.