Microstructures of membrane electrode assembly investigated by polarization analysis neutron small-angle scattering; Water distribution in ion cluster

Koizumi, Satoshi; Putra, A.; Noda, Yohei; Yamaguchi, Daisuke; Tokumasu, Takashi*; Kawakatsu, Toshihiro*

In order to perform a multi-scale observation on a membrane-electrolyte assembly (MEA) of polymer electrolyte fuel cell (PEFC), small-angle neutron scattering (SANS) was recently reinforced by advanced neutron optics. A focusing ultra-small-angle scattering method was developed by using a neutron lens. By combining a double crystal (Bonse-Hart) method, we are able to reach to 10 micron meter length scale, which corresponds to the size of aggregation by carbon powders in an electrode layer. Polarization analysis enables us to selectively remove incoherent scattering from hydrogen atoms and to detect coherent scattering due to ion-cluster of polymer electrolyte (Nafion) and water distribution in it. In order to output structural information in real space, we examined our SANS results by comparing images in real space obtained by low vacuum SEM and multi-scale computer simulations.