Novel Technique of MEA Sample Preparation Using a Focused Ion Beam for Scanning Electron Microscope Investigation

Abstract

A novel technique using a focused ion beam (FIB) set up with a cryo-stage was developed to prepare a flat surface on a membrane electrolyte assembly (MEA) for scanning electron microscope (SEM) observations. The microsample was first trimmed by an ultramicrotome for use in the novel technique. The standard ultramicrotome epoxy block was prepared by "partially-embedding" techniques to suppress the MEA electrode fill up by epoxy resin. An MEA specimen was sampled from the epoxy block and stick to a silver block. The silver block was placed in to an FIB chamber on a cryo-stage and milled at -150{degree sign}C. The SEM image showed flat surface without any thermal damage composed of an interpenetrate structure of carbon particles and ionomer. From the MEA surface acquired by this novel method, we can understand the flooding phenomenon in an electrode porous structure. In addition, the proton conduction through the catalyst layer can be predicted.