Membranes, Electrodes, and Membrane-Electrodes Assemblies Analyzed before and after Operation by Atomic Force Microscopy

Abstract

Material-sensitive and conductive atomic force microscopy was applied to the investigation of cross sections of membrane-electrode-assemblies (MEA) at operating conditions, 80% relative humidity and 75°C, before and after operation. The ionomer content inside the electrodes could be measured due to their characteristic mechanical, chemical and physical properties. By surface potential measurements across MEAs after degrading fuel cell operation, a severe influence of the re-deposited platinum on the potential distribution was found.

Quantitative in Situ Analysis of Ionomer Structure in Fuel Cell Catalytic Layers

“…Atomic force microscopy (AFM) is a high-resolution surface analysis tool. It has been proven to deliver deeper insight into the structure and conductivity of Nafion and Aquivion PFSA ionomer layers, membranes, and electrodes. ,− Using material-sensitive and conductive AFM, different materials can be identified by their properties, which are retrieved as mappings correlating to the topographic data . In the electrode cross-sections, the ionomer layer can be distinguished from carbon and platinum by its higher adhesion force and stiffness (DMT modulus) as well as its lack of electronic conductivity …”

Possible scenario of forming a catalyst layer for proton exchange membrane fuel cells

“…The material-sensitive and conductive atomic force microscopy (AFM) was used to show the ionomer distribution in CL. [13][14][15][16][17][18][19][20][21] The adhesion force image overlaid topography was used to distinguish the ionomer and the aggregated Pt/C. The ionically conductive regions, which implied the ionomer region in CL, could be recognized by their low adhesion signal.…”

“…Cullen 23 showed the ionomer coating lm thickness is about 7 nm using AFM technology. Hiesgen's group [15][16][17][18][19][20][21] had done a series of works on ionomer distribution in the CL by AFM. The AFM tip of nominal radius of less than 1 nm was used and an image pixel size was less than 1 nm (<0.36 nm) for high-resolution image.…”