Electrical Impedance Tomography for Spatial Conductivity Mapping of PEM Fuel Cell Components

Electrical impedance tomography (EIT) was assessed as a measurement approach for spatial conductivity mapping of electrochemical energy system materials such as polymer electrolyte membrane fuel cell components. Polymer electrolyte membranes were selectively activated or deactivated, and defined artificial defects were introduced into catalyst-coated membranes (CCMs) and gas diffusion layers to evaluate the sensitivity and diagnostic capability of EIT. Reconstructed conductivity distributions were independently verified using scanning electrochemical microscopy to confirm spatial contrast and reconstruction accuracy. EIT enabled rapid, nondestructive detection of large-area variations in activation state and degradation. Localized defects were reliably detected, with the methodology prioritizing spatial localization and fault identification providing a distinct advantage over electrical impedance spectroscopy, which lacks the spatial context to distinguish between localized and global degradation. Reproducibility studies on CCMs showed that measurement variability and sample remounting effects remained sufficiently low for consistent defect identification, with defect and background signals clearly separated for different confidence intervals. Simulation studies with different electrode counts and positions, defect arrangements, and sample sizes including a realistic fuel cell application-scale CCM sample were performed as a qualitative design illustration for possible future EIT applications. This development constitutes an important methodological step toward fast nondestructive electrochemical imaging of fuel cell materials and may provide a powerful tool for in-line, in situ, and operando investigations of localized activation, degradation, defects, and heterogeneities in electrochemical energy devices.