Gast ::
| Hauptseite > Publikationsdatenbank > A novel perspective on accelerated degradation studies of proton exchange membranes |
| Hauptseite > Publikationsdatenbank > A novel perspective on accelerated degradation studies of proton exchange membranes |
| Poster (Panel discussion) | FZJ-2025-04274 |
; ; ; ; ; ;
2025
Abstract: Accelerated degradation studies are widely applied in research on proton exchangemembranes (PEMs) for the investigation of the origins and mechanisms of performance lossfor electrolysis or fuel cell applications. In a nutshell, it is reported in literature thatdegradation in PEMs commonly occurs following Fenton-like reactions, where in situ formedH2O2 reacts with transition metal cations to produce radicals. These radicals then alter theionomer on a chemical level by attacking particularly its polar side chains, causing a loss offunctional moieties for proton transport [1]. Fast degradation studies mimic and promotethese conditions by subjecting PEMs to high concentrations of H2O2 and Fe2+ cations atelevated temperatures. However, these studies often exhibit discrepancies when comparedto degradation occurring during long-term operation [2].The presented work attempts to elucidate these discrepancies by i) addressinginconsistencies in accelerated degradation and testing procedures, ii) studying thedependence of degradation on PEM chemistry and structure and iii) utilizing both NMRspectroscopy and SEM microscopy among other techniques for a comprehensive picture.Hereby, solid-state magic angle spinning (MAS) NMR spectroscopy provides information onboth chemical and local structural transformations of the PEM, while SEM offers concreteinsights into structural changes on a microscopic scale.The Fenton-like accelerated degradation experiments were optimized for homogeneity andeffectiveness by introducing the catalytic iron centers into the PEMs. Additionally,interferences in the analytical techniques were minimized by careful removal of excessreactants after accelerated degradation. The combined analytical techniques reveal thatchemical degradation in PEMs is significantly less pronounced than suggested in literature,although differences were observed depending on the type of PEM material. Moreover,organic radicals that form during Fenton-like reactions could not be detected by EPRspectroscopy. However, all samples experienced significant changes in the local structure,as indicated by NMR relaxometry, and microscopic structure, as illustrated by SEMtechniques. Thus, instead of chemical degradation, the PEM may be affected on a structurallevel by mechanical stress due to microscopic gas pockets and macroscopic bubblesforming inside the gas impermeable material.[1] L. Ghassemzadeh et al., J. Am. Chem. Soc. 135, 8181–8184 (2013).[2] J. Mališ et al., Int. J. Hydrogen Energy 41, 2177–2188 (2016).
|
The record appears in these collections: |