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

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.

The development of economic and sustainable technologies for energy conversion and storage is acknowledged to be one of the major milestones that will mitigate climate change and reduce our reliance on fossil fuels. The major advantage of using Anion Exchange Membranes (AEMs) in sustainable hydrogen utilising and generating systems is that they facilitate the use of a wide range of non-precious-metal (potentially Critical Raw Material-[CRM]-free) catalysts, helping to significantly lower costs and improve sustainability.

The research is timely as it responds to the use of renewable electricity generation and the mismatch between generation and use in accord with the UK renewable energy strategy of 15% renewable electricity by 2020. The government commitment to reduce emissions is evident from the recent publication of the Clean Grow Strategy. Energy security involving a diverse and resilient energy mix is at the centre of the document. The UK Industrial Strategy prioritises materials innovations, technologies of tomorrow for more convenient, carbon-friendly living, and innovation drives for affordable and clean energy. In 2016, Materials for Energy Applications was marked as a grow area by EPSRC (balancing capability). However, excluding strategic investments (Faraday and Henry Royce Institutes), there has only been a relatively small increase in the size of this research area since then. The proposed project is in full alignment with all these priorities.

Success in this project through improving the stability of AEMs will represent the required breakthrough, leading to a new era of clean power storage and generation. Our project will have wide-ranging impacts across society, academia, and industry and over a broad range of technologies such as energy conversion and storage (water and carbon dioxide electrolysers, fuel cells, metal air batteries and redox flow batteries) as well as water treatment (electrodialysis and forward osmosis). We have identified two key hydrogen technologies as our focus to demonstrate devices stability and cost savings: solid-state AEM-based alkaline water electrolysers (AEM-AWE) and AEM-based hydrogen fuel cells (AEMFC). To maximise the impact of the project and ensure that the developed materials are tested/validated in commercial configurations, we have included leading UK industrial partners, one for each application (see letters of support). A key impact activity is to embed the postdocs into these companies for 6 months at the end of the project to ensure they are exposed to industrial environments that are related to their project and the specific materials they produced. Exploitation of the potential commercial outputs of the research will be managed by the Enterprise Teams at Newcastle (NCL) and Surrey (SUR), both with extensive experience of successfully negotiating contracts in areas such as collaboration, confidentiality, material transfer and licensing.

An equally important impact is the training of researchers in AEM-related areas to facilitate the industry uptake of this technology through supplying the required skilled workforce. Since this project addresses the challenges of climate change and energy conversion, of significant interest to large sections of the general public, politicians, and industry, there will be many opportunities to communicate our science to these stakeholders. Engagement will be undertaken by the PI, Co-Is, and PDRAs via school lectures, open days, and presentations to relevant UK meetings and trade shows.

The project will help maintain a unique world leading research activity in polymer membrane-based (especially AEMs) energy systems and will provide competitive edge for hydrogen applications for power generation in the mobile, stationary, and auxiliary power sectors. Our long-term vision is to be able to use the same materials in both AEMFCs and AEM-AWEs, to facilitate commercialisation and the use of hydrogen as an energy storage vector.