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| Home > Publications database > Degradation studies of a short-side-chained PFSA material for industrial water electrolysis by MAS and PFG-NMR |
| Poster (Panel discussion) | FZJ-2024-00267 |
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2023
Abstract: As the ongoing climate change demands alternative energy sources to fossil fuels, the acidic water electrolysis to produce green hydrogen is growing in importance. A critical cornerstone of an electrolyser for acidic water electrolysis is the proton exchange membrane (PEM), which is intended to provide reliable separation of the anode and cathode compartments while ensuring high proton conductivity. In addition, the PEM serves as a carrier for the electrode material to form a membrane electrode assembly (MEA).To operate acidic water electrolysis economically the PEM must be resistant to degradation in order to maximize its lifetime. On a molecular level the polymer is attacked by radicals formed in various side reactions during electrolysis. The influence of the MEA preparation procedure on PEM degradation has been rarely discussed so far. In addition, the electrodynamic parameters of the acidic water electrolysis itself affect the stability and lifetime of a PEM polymer.1Nuclear magnetic resonance (NMR) spectroscopy has proven to be a powerful method for analysing the structural properties of polymers and ionomers. For this reason, NMR spectroscopy was used to study the changes in PEM structure and properties during MEA preparation and electrolysis operation. Thereby, it was essential to find a suitable reference point that allows a quantitative evaluation of the various influences on PEM degradation. In this work changes in chemical structure of a short-side-chained perfluorinated ionomer were investigated using 19F MAS NMR experiments. The relaxation times of the functional groups before and after PEM degradation were compared to detect changes concerning the mobility and chemical environment of the functional groups. The observed relaxation data suggest that degradation decreases the mobility of the individual groups due to chain fracture and crosslinking, as it has already been demonstrated for long-side-chained PEMs.2 In addition, the signal intensities of the individual functional groups before and after PEM degradation have been tracked to identify sites that are vulnerable to degradation. These data suggest that the side chain is more degraded than the polymer backbone. In addition, PFG-NMR was applied to study the proton conductivity as a function of PEM degradation, where the water uptake ratio plays a major role.3Literature:[1] S. H. Frensch et al., International Journal of Hydrogen Energy 2019, 44, 29889-29898[2] L. Ghassemzadeh et al., The Journal of Physical Chemistry C 2010, 114, 34, 14635-14645[3] Ochi et al., Solid State Ionics 2009, 180, 6-8, 580-584
Keyword(s): Energy (1st) ; Chemistry (2nd)
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