Poly(vinyl alcohol-co-vinyl acetal) gel electrolytes for alkaline water electrolysis

Yifan Xia, Sinu Rajappan, Dmytro Serhiichuk, Mikkel Rykær Kraglund, Jens Oluf Jensen, David Aili*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

A series of poly(vinyl alcohol-co-vinyl acetal) gel electrolytes was synthesized, characterized and assessed as electrode separators in alkaline water electrolysis. The copolymers were prepared by reacting poly(vinyl alcohol) with benzaldehyde or 4-formylbenzoic acid under acidic conditions at different ratios, and visually homogenous and water-insoluble membranes were subsequently obtained by solution casting. The physicochemical characteristics in terms of electrolyte uptake, swelling behavior, and ion conductivity could be tuned by varying the degree of functionalization. At a moderate vinyl acetal content of 5%, the membrane combined mechanical robustness with ion conductivity reaching 36 mS cm−1 in 30 wt% aqueous KOH at room temperature. Current densities of up to 1000 mA cm−2 were reached with uncatalyzed Ni-foam electrodes at a cell voltage of less than 2.6 V in alkaline water electrolysis tests, while the membrane effectively prevented hydrogen crossover. Although apparent membrane degradation was observed after a few days of electrolysis operation, the strategies presented in this work to tune membrane properties are of general relevance to the field towards the development of new ion-solvating membrane systems based on more alkaline stable and robust backbone chemistries.
Original languageEnglish
Article number121719
JournalJournal of Membrane Science
Volume680
Number of pages10
ISSN0376-7388
DOIs
Publication statusPublished - 2023

Bibliographical note

This work was financially supported by the European Union's Horizon 2020 Research and Innovation Action program (grant agreement 862509, NEXTAEC).

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