PEMFC Water Transport and Material Properties Correlated with Neutron Diagnostic Methods

Jeff Gagliardo (GM)

Metrology methods based on neutron beam attenuation are well-suited to diagnostic applications in a variety of practical electrochemical energy systems. In the area of hydrogen fuel cells, liquid water formed as a product of the electrochemical reaction can be imaged in-situ with high temporal and spatial resolution, due to the large neutron cross-section of hydrogen. Collaborative research between the National Institute of Standards and Technology (NIST) and General Motors has used detectors with spatial resolutions of 100 .m or better for measurements acquired in the plane of the MEA and neutron detectors with spatial resolution ~13 .m to resolve water gradients normal to the membrane electrode assembly (MEA) and at critical material interfaces. The applicability of the proposed measurements are enhanced by a fuel cell test section with distributed measurements of temperature, current density, and ohmic resistance. Using these tools variations in GDL thermal conductivity, thickness, and durability are evaluated for optimized water removal at various shutdown conditions.

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