Neutron imaging is a completely non-destructive probe of the water content in operating fuel cells. However, the spatial and temporal resolution of the method limits the application range. We report on our continued imaging detector resolution improvements, where we have achieved a spatial resolution of 2 µm. We applied this new detector capability to measure the water content of two different membrane/electrode assemblies where the ionomer to carbon mass ratio (I/C) was the only variable. A 1 cm²active area test section with parallel flow channels was operated as a differential cell at 80 °C at constant voltage. Shown in the figure are the imaged water content at 0.4 V, 100% inlet relative humidity for the I/C = 0.9 and I/C = 1.1.

Figure Caption: Neutron images of the water content of an operating fuel cell at 0.4 V; a) I/C of 1.1, b) 2I/C of 0.9. In both cases, the cathode is toward the top of the image and the anode toward the bottom.

The authors from LANL are supported by DOE Fuel Cell Technologies Office, through the Fuel Cell Performance and Durability (FC-PAD) Consortium; Fuel Cells program manager: Dimitrios Papageorgopoulos. The authors from NIST are supported by the U.S. Department of Commerce, the NIST Radiation and Physics Division, the Director's office of NIST, the NIST Center for Neutron Research, and the Department of Energy interagency agreement No. DE_AI01-01EE50660, program manager: Nancy Garland.