Year-end Sale % OFF 
Abstract
abstract Low-density polyethylene (LDPE)-based anion exchange membranes (AEMs) with 65% degree of grafting of vinylbenzyl chloride (VBC) were tethered with different amine functionalities namely, trimethyl amine (TMA), 1,4-diazabicyclo[2.2.2]octane (DABCO), 1-azabicyclo[2.2.2]octane (ABCO) and N-methylpiperidine (NMP), and were subjected to degradation test by immersing the OH − exchanged AEMs in deionised water at 60 °C, a condition analogous to fuel cell and electrolyser environment. All the quaternised membranes, regardless of the tethered amine functional group, exhibited similar degradation loss of ca. 5% IEC per month. Benzylic peroxide was detected in the degradation solution in all the tested AEMs. The observed degradation of the OH − exchanged AEMs was mainly attributed to peroxide and hydroxide radical attacks on the ternary (benzylic) carbon resulting in the release of vinylbenzyl trimethylammonium hydroxide (VBTMA) as a whole which was also detected. The degradation test performed on TMA-functionalised membrane under nitrogen, oxygen and 3 wt% H 2 O 2 showed similar degradation products namely benzylic peroxide and VBTMA suggesting that the degradation mechanisms under these three conditions are similar. The over three-fold increase in the degradation rate under oxygen saturated solution compared to nitrogen is due to the higher peroxide concentration produced from oxygen reduction to superoxide via ylide.
Highlights
The development of solid anion exchange membrane (AEM) as an alternative to liquid KOH solution as electrolyte paved the way for the renewed interest in alkaline fuel cell and electrolyser applications
We have recently reported that, in close to neutral and low alkalinity solutions, typical of that in anion exchange membrane fuel cell (AEMFC) and water electrolyser (AEMWE), AEM degradation in terms of ion exchange capacity (IEC) loss was not mainly due to OHÀ ion attack on the trimethylamine (TMA) functional groups proposed above, but mainly due to the removal of the vinylbenzyl trimethylammonium (VBTMA) group as whole [12]
The slightly higher degradation rate in DABCO could be due to the difficulty in obtaining 100% mono-quaternisation and the presence of small amount of bis-quaternised DABCO which converts into a piperazine less stable structure as discussed previously
Summary
The development of solid anion exchange membrane (AEM) as an alternative to liquid KOH solution as electrolyte paved the way for the renewed interest in alkaline fuel cell and electrolyser applications. We have recently reported that, in close to neutral and low alkalinity solutions, typical of that in anion exchange membrane fuel cell (AEMFC) and water electrolyser (AEMWE), AEM degradation in terms of IEC loss was not mainly due to OHÀ ion attack on the trimethylamine (TMA) functional groups proposed above, but mainly due to the removal of the vinylbenzyl trimethylammonium (VBTMA) group as whole [12]. Previous attempts to investigate AEM degradation used density functional theory (DFT) [21,41,42] and model compounds [40,43e45] instead of grafted or synthesised AEMs. In this research, LDPE-based AEMs were used and the investigation was extended to include the effect of employing other functional groups aside from TMA to the resulting stability of the functionalised membrane, namely, DABCO, ABCO and NMP immersed in deionised water. The investigations of the degradation of hydroxideexchanged AEM reported were performed in water/deuterated water media with very low alkalinity in order to mimic the real operating conditions of fuel cells/electrolysers and so that the degradation by-products can be conveniently and directly analysed by 1H NMR spectroscopy
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
