Imaging and microanalysis of thin ionomer layers by scanning transmission electron microscopy

Journal Article · Wed Jan 01 00:00:00 EST 2014 · Journal of the Electrochemical Society

DOI:https://doi.org/10.1149/2.1091410jes· OSTI ID:1154823

Cullen, David A ^[1]; Koestner, Roland ^[2]; Kukreja, Ratan ^[2]; Minko, Sergiy ^[3]; Trotsenko, Oleksandr ^[3]; Tokarev, Alexander V ^[1]; Guetaz, Laure ^[4]; Meyer, III, Harry M ^[1]; Parish, Chad M ^[1]; More, Karren Leslie ^[1]

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1. ORNL
2. General Motors Corporation
3. Clarkson University, Potsdam, NY
4. French Atomic Energy Commission (CEA), Grenoble

Improved conditions for imaging and spectroscopic mapping of thin perfluorosulfonic acid (PFSA) ionomer layers in fuel cell electrodes by scanning transmission electron microscopy (STEM) have been investigated. These conditions are first identified on model systems of Nafion ionomer-coated nanostructured thin films and nanoporous Si. The optimized conditions are then applied in a quantitative study of the ionomer through-layer loading for two typical electrode catalyst coatings using electron energy loss and energy dispersive X-ray spectroscopy in the transmission electron microscope. The e-beam induced damage to the perfluorosulfonic acid (PFSA) ionomer is quantified by following the fluorine mass loss with electron exposure and is then mitigated by a few orders of magnitude using cryogenic specimen cooling and a higher incident electron voltage. Multivariate statistical analysis is also applied to the analysis of spectrum images for data denoising and unbiased separation of independent components related to the catalyst, ionomer, and support.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
• Sponsoring Organization: USDOE
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1154823
• Journal Information: Journal of the Electrochemical Society, Vol. 161, Issue 10; ISSN 0013--4651
• Country of Publication: United States
• Language: English