Local Electrical Resistance and Electrochemical Impedance Response of a Proton Exchange Membrane Electrolyzer Anode

High Resolution Image Download MS PowerPoint Slide Optimizing membrane electrode assemblies (MEAs) of proton exchange membrane electrolyzer cells (PEMECs) is crucial for cost-effective green hydrogen production and requires postoperation characterization. This study uses cross-section analysis, four-point-probing (4PP), Raman spectroscopy, and alternating current scanning electrochemical microscopy (AC-SECM) to examine local aging effects of an operated anode. Operation increased sheet resistance, promoted by partial oxidation of the highly conductive metallic Ir. While low-magnification imaging suggested a constant anode thickness, higher-resolution imaging revealed an Ir-rich sublayer formed by Ir migration toward the cathode. Despite the increased sheet resistance, in situ AC-SECM revealed a reduced normalized electrochemical impedance response after operation. This is due to an increase in the conductive electrode surface caused by a loss of insulating ionomer. Local compaction through the porous transport layer (PTL) may counteract this effect by reducing accessible catalyst surface area within the SECM-sensitive volume, resulting in impedance differences depending on the PTL contact history. This study advances understanding of anode aging by emphasizing structural, chemical, and mechanical changes at local PTL contacts, and applies AC-SECM to PEMEC anodes to correlate property changes toward assessing local electrochemical activity.