Atomic Force Microscopy Investigation of Polymer Fuel Cell Gas Diffusion Layers before and after Operation

Abstract

The ageing of microporous layers (MPL) of fuel cell gas diffusion layers has been analyzed using a special atomic force microscopy technique. The mean local adhesion force on the surface as well as the energy dissipation on the same area has been used as a measure for changes of surface properties corresponding to ageing of the MPL. The samples have been studied before and after fuel cell operation. In all cases, the changes due to operation are stronger on the cathode compared to the anode. The results from measurements under comparably dry and wet conditions are consistent with an increased loss of polytetrafluoroethylene (PTFE) at the cathode which leads to a hydrophobicity loss.

PTFE Distribution in High-Temperature PEM Electrodes and Its Effect on the Cell Performance

“…Beside morphology and topography, the AFM is also capable of measuring the local conductivity of the sample. These techniques were previously used to characterize low temperature Nafion-based electrolyte fuel cell membranes and electrodes [8,9], and we find they are especially suited for HT-PEM electrodes due to the distinctive spherical shape of the non conductive PTFE binder. Size distribution of conductive areas in the catalyst layer was analyzed with AFM and the electrode structure was determined with SEM.…”

Analysis of Aged Polymer Electrolyte Fuel Cell (PEFC) Components by Nontraditional Methods

“…Atomic force microscopy (AFM) is a versatile tool for the analysis of surface properties and has been shown to be quite valuable for the investigation of components and materials used in PEM fuel cells [1][2][3][4][5][6]. Especially, the novel technique based on fourier synthesis of the force separation curve at every image point deliver material sensitive information (HarmoniX mode by Bruker Corp.).…”

“…Thereby, in addition to the classical phase shift which indicates the total energy loss, adhesion forces, dissipation energy, peak forces and hardness can be separately measured. Since the properties of membranes, electrodes and gas diffusion layers are dependent on nanoscale structure of the materials valuable information can be derived [6]. In addition, infrared spectroscopy (IR) was used to analyze the PTFE content of electrodes and gas diffusion layer material from the C-F vibration intensities.…”