High resolution in plane imaging of electrochemical systems

In conventional through plane imaging the neutron beam is perpendicular to the membrane. To image the distribution between the different cell layers, high resolution in plane imaging can be used, where the neutron beam is parallel to the membrane. Due to the low thickness of the fuel cell layers (e.g. 200 µm for a GDL), high resolution is required. To optimize the trade-off between spatial and temporal resolution, we developed a set of anisotropic resolution enhancement methods [1, 2] as the high spatial resolution is only required in one direction, namely across the membrane. This allows obtaining a sufficient resolution to resolve the different layers while keeping reasonable exposure times.

  • Effective spatial resolution of 20 µm for small scale and middle size cells up to 120 mm length (suitable to resolve profiles of water distribution across the GDLs)
  • Effective spatial resolution of 50 µm for long cells up to 300 mm length (suitable to separately resolve the water content of the GDLs in the anodeand the cathode )
  • Typical exposure times: 5 – 20 seconds
  • The active area size in the direction of the beam is limited to ~20 mm
  • Possibility to measure several small scale fuel cells simultaneously with our multi-cell setup
Example: Freezing during isothermal sub-zero startup [3]. In the example above, a small scale fuel cell was started in isothermal conditions at -10°C. Water produced in super-cooled state is transported through the GDL to the cathode flow channels. Approximately 14 minutes after the startup, water freezes and cannot be transported anymore through the GDL, resulting in accumulation in the catalyst layer, as evidenced by the sudden increase of water content localized in the central part of the cell.

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