STXM Characterization of PEM Fuel Cell Catalyst Layers

Abstract

The synchrotron based scanning transmission soft X-ray microscopy (STXM) utilizing near edge X-ray absorption fine structure (NEXAFS) is a novel technique for characterization of membrane electrode assembly (MEA) components in proton exchange membrane fuel cells (PEMFC). Component maps for carbon support, Pt and ionomer in the cathode catalyst layer and perfluorosulphonic acid (PFSA) membrane including the reinforced layer have been obtained from full C 1s multi-energy image sequences and maps from images at four energies in the C 1s and F 1s regions. The ability of this technique to distinguish both structural and chemical differences in cathode catalyst layers from two significantly different designs has been demonstrated. The ionomer distribution in the cathode catalyst layer of an advanced catalyst coated membrane (CCM) structure is compared to that of the cathode in a gas diffusion electrode (GDE).

Characterizing automotive fuel cell materials by soft x-ray scanning transmission x-ray microscopy

“…These include development of dose-and time-efficient methods for quantitative mapping of ionomer in microtomed sections of membrane electrode assemblies [3,4]; in situ studies of effects of hydration at ambient temperature [5]; and 3D mapping of chemical species using multi-photon energy spectro-tomography [6]. STXM methods have been applied to studies of the role of the Pt-precursor on Pt degradation chemistry [7,8]; the fate of the PFSA ionomer during degradation by carbon corrosion [9]; ink-jet printed catalyst layers [10]; and the role of the perylene support in fabrication, assembly and degradation of alternative, nanostructured thin film catalysts [11,12].…”

Atomic Force Microscopy on Cross Sections of Fuel Cell Membranes, Electrodes, and Membrane Electrode Assemblies

“…This complex functionality is normally achieved by mixing ionomer with the catalytically active nanometer platinum particles supported on carbon. The size and distribution of the components, especially of the ionomer in the catalyst layer, determines the performance and stability of the electrodes, i.e., based on the volume of the electrochemically active catalyst area, which affects the proton conductivity, mass transport, electronic conductivity, and porosity [33].…”

“…Recently, the analysis of components in fuel cell has been performed using synchrotron based soft X-ray scanning transmission microscopy (STXM) [33], [38], [39]. The chemical contrast between the elements is facilitated using the near edge X-ray absorption with a spatial resolution of 30 nm.…”

Progress in Soft X-ray Microscopy Characterization of PEM Fuel Cell Catalyst Layers

“…For a given radiation dose, it can provide better spectroscopic chemical characterization than analytical transmission electron microscopy (TEM) using electron energy loss or X-ray fluorescence methods. Given the very high sensitivity of the perfluorosulfonic acid (PFSA) membrane and ionomer to radiation damage [4], there are significant advantages to using X-ray microscopy for mapping ionomer in MEAs [2,3]. An example of quantitative mapping of ionomer in catalyst layers in 2D projection by STXM is presented in Fig.…”