Over the last decade or so, RG-AEMs with more than 100 different chemical configurations have been fabricated. Most of these have not been studied in detail as the focus was traditionally on RG-AEMs for use in alkaline membrane fuel cells where AEMs needed to have good stabilities in alkali. This has meant the focus was only on a small number of these chemistries. However, other electrochemical applications, such as electrodialysis (ED) and reverse electrodialysis (RED, a salinity gradient power technology) require AEMs to be operating in more neutral pH environments. This allows a wider range of chemistries to be used. For such applications, properties such as permselectivity and fouling resistance can be as important as ion conductivity.
This presentation will provide a summary of recent RG-AEM developments at Surrey. A focus will be on the study of AEM chemistries for potential use in RED, with a study on the effects of crosslinking, head-group chemistry, and ion-exchange capacity. It has been found that despite being highly ionically conductive, non-crosslinked RG-AEMs have intrinsically low permselectivities and are prone to excessive levels of swelling in water (especially at high ion-exchange capacities). The incorporation of crosslinking can improve permselectivities, and lower swelling, but this often leads to detrimental drops in ion conductivity. Interestingly, the choice of head-group chemistry can have an effect on properties such as permselectivity.
This research has been funded by EPSRC grants EP/M014371/1, EP/M022749/1, EP/R044163/1, and EP/T009233/1 along with EU Project SELECTCO2 (grant agreement 851441).
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