Abstract
Ionomer distribution in catalyst layers has gathered much attention to understanding transport phenomena. In this study, a novel visualization method of the overall through-plane ionomer distribution in the catalyst layers by using a two-stage ion-beam processing is suggested. The first stage is the formation of flat and smooth cross-section by a broad ion beam. The second stage is the selective removal of the materials in the catalyst layer by a focused ion beam. Scanning ion microscopic images were obtained after the first and second stage. Then ionomer distribution was extracted by image processing. The ionomer distribution of the catalyst layer with ionomer to carbon ratio of 2.0 was analyzed. The through-plane ionomer distribution was inhomogeneous. Thin ionomer layer was formed at the interface with the polymer electrolyte membrane. This can be because of deposition of ionomer during solvent evaporation in the fabrication process.