Membrane chemical degradation spectroscopy

On the basis of results from micro-Raman spectroscopy, severe side degradation is found around the platimum redeposition line (Ohma et al. 2007a). The sulfate ion release rate on the cathode side is more than that on the anode side. A similar trend is also observed for the ERR. The results strongly support the role of the platinum line in membrane chemical degradation. 

Energy dispersive X-ray spectroscopy (EDX) is used predominantly for elemental analysis or chemical characterization. The advantage of this technique is that it can identify the elemental composition for a small area thus, a profile of element composition can be created across the sample. Since EDX tests are usually conducted in a scanning electron microscope, a composition profile can be directly overlaid onto a secondary scanning electron microscope micrograph. Major elements related to membrane chemical degradation such as fluorine, sulfur, platinum and other metals can be readily detected. 

L. Ghassemzadeh, K.-D. Kreuer, J. Maier, K. MueUer, Chemical degradation of NAFION membranes under mimic fuel cell conditions as investigated by sohd-state NMR spectroscopy, J. Phys. Chem. C 114 (2010) 14635—14645. 

Ghassemzadeh, L., Marrony, M., Barrera, R., Kreuer, K. D., Maier, and Muller, K. 2009. Chemical degradation of proton conducting perfluorosulfonic acid ionomer membranes studied by solid-state nuclear magnetic resonance spectroscopy. Journal of Power Sources 186 334-338. 

In addition to the radical attack of the end group, hydroxyl radical OH will attack the C-S and C-O-C bond in the copolymer side chain. Loss of a great number of sulfonate gronps or whole side chains would affect the proton conductivity of the membranes. Ghassemzadeh et al. studied chemical degradation of PFSA after fuel cell in sitn tests by solid-state NMR spectroscopy. The NMR spectra prove that degradation mostly takes place within the polymer side chains. ... 

Raman scattering by gases is not a very strong effect and gives only weak signals. So gas permeation is usually not measurable by Raman spectroscopy. However, degradation of some chemical components consecutive to gas permeation can be detected in situ by Raman spectroscopy any formation of a deposited solid (carbon for instance) allows its identification and evaluation of membrane degradation [51],... 

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