Impregnation methods for quantitative analyses of the gas diffusion layer in proton exchange membrane fuel cells

Abstract

Microstructural analysis is central to understand and predict the performance and degradation of proton exchange membrane fuel cell (PEMFC) materials. Advanced electron and x-ray 3-D microscopy methods are needed to characterize the reticulate structures forming the catalyst, gas diffusion layer/ microporous layers. The high-throughput dual beam scanning electron microscope allows the 3-D imaging of such layers with a spatial resolution in the range of a few nm. However, for accurate quantitative analyses, impregnation of the porous sample is required to mitigate artefacts due to milling and pore-through effect, and provide sufficient contrast between the material phases for image segmentation. This study investigates an impregnation method based upon the addition of Cobalt (II) acetylacetonate nanoparticles in an epoxy polymer resin. The results were compared with conventional methods using commercial resins stereology on sections polished by focused ion beam (FIB). The results indicate the appropriateness of the newly proposed method, providing adequate contrast for accurate image segmentation. An Energy Dispersive X-ray (EDX) analysis was included to obtain an information about the composition, which can be used for further improvements of the resin.