Abstract
Giron Rodriguez et al. [ACS Sustainable Chem. Eng., 2023, 11, 1508] previously showed that radiation-grafted anion-exchange membranes containing N-benzyl-N-methylpiperidinium headgroups (MPIP-RG-AEM) are promising for use in CO2 electrolysis (cf. commercial and other RG-AEM types). For a more sustainable synthesis, MPIP-RG-AEMs have now been fabricated using a reduced 1.1 times excess of amine reagent (historically made using >5 times excess). A resulting RG-AEM promisingly had a bulk amination level that was comparable to those made with the traditional large excess. Unexpectedly, however, it had a significantly reduced water content, with two further batches showing that this observation was repeatable (and reproducible via measurements collected on a single batch using different techniques in different labs). The ionic conductivities of the RG-AEM made with a controlled 1.1 excess of amine were also lower, with higher activation energies. Terahertz time-domain spectroscopy measurements showed that the lower water uptake RG-AEMs, made with the 1.1 amine excess, contained smaller amounts of bulk water relative to bound water (a repeatable observation with different counter-anions). This lack of bulk water, yielding reduced water diffusion coefficients, led to a change in the water management when such RG-AEMs were tested in CO2 electrolysis cells, with significantly affected in situ performances. Small angle scattering data (X-ray and neutron) indicated that MPIP-RG-AEM fabrication with the 1.1 excess of amine reduced the size of the amorphous lamella domains on hydration, and this change is suspected to be the cause of the lower water uptakes and swelling. The finding that chemically similar AEMs can have significantly different hydration properties is potentially important to all ion-exchange membrane users and developers (beyond the CO2 electrolysis scope of this study).
| Original language | English |
|---|---|
| Pages (from-to) | 20724-20740 |
| Number of pages | 17 |
| Journal | Journal of Materials Chemistry A |
| Volume | 11 |
| Issue number | 38 |
| DOIs | |
| Publication status | Published - 8 Sept 2023 |
| Externally published | Yes |
Bibliographical note
Publisher Copyright:© 2023 The Royal Society of Chemistry
Funder
This research was primarily funded by the European Union's Horizon 2020 research and innovation programme under grant agreement no. 851441 (project SELECTCO2, led by DTU). The resources used for conductivity experiments were funded by the UK Engineering and Physical Sciences Research Council (EPSRC) grant EP/T009233/1. The Raman microscope was funded by EPSRC grant EP/M022749/1. We thank Dr Sam Page (Solid-state NMR Service, University of Durham) for recording the solid-state NMR spectra (data in Fig. 4 and 5). DTU would also like to acknowledge support from the Villum Foundation's VSustain center (project # 9455). The Lancaster team acknowledges support from EPSRC H2FC Supergen Flexible Grant EP/P024807/1, the Royal Academy of Engineering for funding Dr Lin's Industrial Fellowship, the Centre for Global Eco-Innovation PhD Programme, Dr Riccardo Degl'Innocenti for THz-TDS equipment access, and discussions with Dr Gaurav Gupta. The Newcastle team's dynamic water sorption work were resourced from EPSRC grant EP/T00939X/1. The UCL team acknowledges EPSRC for funding (grants EP/V057863/1 and EP/W033321/1), ISIS (Harwell, STFC, UK) for neutron beamtime (https://doi.org/10.5286/ISIS.E.RB2291004-1), and gratefully acknowledge Dr Han Wu and the EPSRC CNIE research facility service (EPSRC Award, EP/S03305X/1) at University College London for assisting the collection of SAXS data. The University of Surrey also thanks Dr Friedrich Menges for granting a free licence for use of the Spectragryph software: https://www.effemm2.de/spectragryph/index.html.ASJC Scopus subject areas
- Chemistry(all)
- Renewable Energy, Sustainability and the Environment
- Materials Science(all)
