期刊
CHEMSUSCHEM
卷 15, 期 22, 页码 -出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/cssc.202201571
关键词
anion exchange membranes; fuel cells; quaternary ammonium; radical reactions; radiolysis
资金
- Swiss National Science Foundation (SNSF) [175493]
This study evaluated the susceptibility of four benzylic-type quaternary ammonium compounds with different electron density to degradation by radicals. The results showed that electron-donating groups promoted radical degradation, while electron-withdrawing groups increased stability. Therefore, both durability against radical-induced degradation and alkaline stability need to be considered in the rational design of novel anion-exchange membranes.
Four benzylic-type quaternary ammonium (QA) compounds with different electron density at the phenyl group were evaluated for their susceptibility against degradation by radicals. Time-resolved absorption spectroscopy indicated that radicals with oxidizing and reducing character were formed upon oxidation by HO center dot and O center dot- (conjugate base of HO center dot). It was estimated that, dependent on the QA, 18-41 % of the formed radicals were oxidizing with standard electrode potentials (E-0) above 0.276 V and 13-23 % exceeded 0.68 V, while 13-48 % were reducing with E-0 < -0.448 V. The stability of these model compounds against oxidation and reductive dealkylation was evaluated at both neutral and strongly alkaline conditions, pH 14. Under both conditions, electron-donating groups promoted radical degradation, while electron-withdrawing ones increased stability. Therefore, durability against radical-induced degradation shows an opposite trend to alkaline stability and needs to be considered during the rational design of novel anion-exchange membranes for fuel cells and electrolyzers.
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