Next generation anion-exchange membranes (AEM) with covalently-bound antiradical functions for enhanced durability

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The prime motivation in the development of anion-exchange membrane-(AEM)-based fuel cells (AEMFC) and alkaline water electrolysers (AEM-AWE), that use (generate electricity) and produce sustainable hydrogen respectively, is the potential to minimise the use of precious metal electrocatalysts (cf. proton-exchange membrane equivalents); this will reduce costs and lead to systems involving only earth abundant elements (ensures sustainability). Additionally, AEM-AWEs use low-concentration aqueous-alkali or pure-water feeds (cf. traditional non-AEM alkaline water electrolysers), eliminating the need to handle large quantities of highly caustic solution (that comes with significant environmental implications related to leakage and disposal).The AEMFCs will initially be targeted in the backup power stationary sector (including for telecoms) to replace diesel generators with the added consumer convenience of reduced noise and local emissions of pollutants: the current diesel generation market supplies 200 GW of global power demand (valued at £9B in 2015). The global hydrogen electrolyser market is estimated to register a compound annual growth rate of 7.2% between 2018-28 (market expected to reach US$426.3M by 2028), with application in the transport segment expected to grow at a significant pace in Western Europe ["Hydrogen Electrolyzer Market: Alkaline Electrolyzer Expected to Remain Dominant Product Type Through 2028: Global Industry Analysis 2013-17 and Opportunity Assessment 2018-28", Future market insights report, 2019].The applicants are world-leaders in the development of alkaline polymer electrolyte materials (membranes and powdered forms, the latter for use in electrode manufacture), especially radiation-grafted types. Mechanically robust, alkali stable, and high performance (high conductivity, high water transport) materials have been demonstrated for use in both AEMFCs and AEM-AWEs (temperatures up to 80 degC). The recent improvements in alkali stability means that oxidative-radical degradation mechanisms become relatively significant and now need to be a research focus. The focus of this project is to develop two classes of AEM with further enhanced chemical stabilities (both alkali and radical-oxidative), but where mechanical, ion-transport and water transport properties are not sacrificed: (1) next generation radiation-grafted AEMs (RG-AEM) and (2) new dimensionally-stable, mechanically-strong pore-filled AEMs (PF-AEM).Firstly, the focus will be on the co-incorporation of vinyl-phenolic components into RG-AEMs, where such covalently-bound phenolic components can act as radical traps to enhance radical-oxidative stabilities. Secondly, our prior RG-AEM research has also identified several new advanced monomers (such as the 3-vinylbenzyl chloride) that can form RG-AEMs with enhanced alkali stabilities but, unfortunately, poor ion conductivities and water transport properties (as such monomers cannot be made to radiation-graft at adequate levels, due to the crude radical-based nature of such grafting). Hence, these advanced monomers will be used to make PF-AEMs, which can be fabricated using alternative polymerisation methods (e.g. cationic or advanced controlled-radical polymerisation). Thirdly, co-incorporation of vinyl-phenolic monomers will also be possible with these new PF-AEMs to produce materials with maximised chemical and mechanical stabilities.The RG-AEMs and PF-AEMs will be evaluated in both AEMFCs and AEM-AWEs, to maximise the commercialisation opportunities. This will heavily involve our industrial project partners: AFC Energy (Dunsfold, Surrey) will assist with translating the materials developments into pilot scale AEMFC demonstrator systems, using their fuel cell component integration knowhow and IP (for the backup power sector). PV3 Technologies (Cornwall) will assist with AEM-AWE developments by materials exchange and evaluation and scale-up of AEM-AWE technology in their facilities.