Defect propagation at the anode in Polymer Electrolyte Membrane Fuel Cells

International audience; Defaults propagation in Membrane Electrode Assemblies (MEA) of Polymer Electrolyte Membrane Fuel Cells (PEMFC) was investigated through an Accelerated Stress Test (AST) consisting load (and thus potential) cycling, load driven RH cycling and Open Circuit Voltage. Customized MEA without and with several defects at the anode Catalyst Layer (CL), i.e. lack or over thickness, at two different locations (near the hydrogen inlet or near the hydrogen outlet) were fabricated and subjected to the AST. Electrochemical characterization was performed periodically using a segmented cell which allows to follow the evolution of the cell performance, as well as anode and cathode and ElectroChemical Surface Area (ECSA) over the test period with a spatial resolution along the gas channels. The primary results indicate a significant impact of the default on the aging rates in all cases, as well as a significant impact on the default location in the case of the MEA with a default of the anode CL near the hydrogen inlet: we observed a default propagation along the hydrogen flow direction monitored through the evolution of local ECSA and its standard variation between the beginning and the end of the test. The segments neighboring the defect seemed more affected than the others. No significant impact was evidenced however when the default was located near the anode outlet. These observations were completed by post-mortem analysis of the membrane following the AST: the MEA with a lack of anode CL evidenced thinning of the PFSA layer on the cathode side near the location of the default.