Cycloaliphatic Quaternary Ammonium Functionalized Poly(oxindole biphenyl) Based Anion-Exchange Membranes for Water Electrolysis: Stability and Performance
Mechanically robust anion-exchange membranes (AEMs) with high conductivity and long-term alkali resistance are needed for water electrolysis application. In this work, aryl-ether free polyaromatics containing isatin moieties were prepared via super acid-catalyzed copolymerization, followed by functi...
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| Format: | Article |
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MDPI AG
2023-12-01
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| Series: | Polymers |
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| Online Access: | https://www.mdpi.com/2073-4360/16/1/99 |
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| author | Sara Gjoshi Paraskevi Loukopoulou Michaela Plevova Jaromir Hnat Karel Bouzek Valadoula Deimede |
| author_facet | Sara Gjoshi Paraskevi Loukopoulou Michaela Plevova Jaromir Hnat Karel Bouzek Valadoula Deimede |
| author_sort | Sara Gjoshi |
| collection | DOAJ |
| description | Mechanically robust anion-exchange membranes (AEMs) with high conductivity and long-term alkali resistance are needed for water electrolysis application. In this work, aryl-ether free polyaromatics containing isatin moieties were prepared via super acid-catalyzed copolymerization, followed by functionalization with alkaline stable cyclic quaternary ammonium (QA) cationic groups, to afford high performance AEMs for application in water electrolysis. The incorporation of side functional cationic groups (pyrrolidinium and piperidinium) onto a polymer backbone via a flexible alkyl spacer aimed at conductivity and alkaline stability improvement. The effect of cation structure on the properties of prepared AEMs was thoroughly studied. Pyrrolidinium- and piperidinium-based AEMs showed similar electrolyte uptakes and no obvious phase separation, as revealed by SAXS and further supported by AFM and TEM data. In addition, these AEMs displayed high conductivity values (81. 5 and 120 mS cm<sup>−1</sup> for pyrrolidinium- and piperidinium-based AEM, respectively, at 80 °C) and excellent alkaline stability after 1 month aging in 2M KOH at 80 °C. Especially, a pyrrolidinium-based AEM membrane preserved 87% of its initial conductivity value, while at the same time retaining its flexibility and mechanical robustness after storage in alkaline media (2M KOH) for 1 month at 80 °C. Based on <sup>1</sup>H NMR data, the conductivity loss observed after the aging test is mainly related to the piperidinium degradation that took place, probably via ring-opening Hofmann elimination, alkyl spacer scission and nucleophilic substitution reactions as well. The synthesized AEMs were also tested in an alkaline water electrolysis cell. Piperidinium-based AEM showed superior performance compared to its pyrrolidinium analogue, owing to its higher conductivity as revealed by EIS data, further confirming the ex situ conductivity measurements. |
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| language | English |
| last_indexed | 2024-03-08T14:59:26Z |
| publishDate | 2023-12-01 |
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| series | Polymers |
| spelling | doaj.art-7afd163fd50147dc8aa21459961f5ee72024-01-10T15:06:49ZengMDPI AGPolymers2073-43602023-12-011619910.3390/polym16010099Cycloaliphatic Quaternary Ammonium Functionalized Poly(oxindole biphenyl) Based Anion-Exchange Membranes for Water Electrolysis: Stability and PerformanceSara Gjoshi0Paraskevi Loukopoulou1Michaela Plevova2Jaromir Hnat3Karel Bouzek4Valadoula Deimede5Department of Chemistry, University of Patras, GR-26504 Patras, GreeceDepartment of Chemistry, University of Patras, GR-26504 Patras, GreeceDepartment of Inorganic Technology, University of Chemistry and Technology, Prague, Technická 5, 16628 Prague, Czech RepublicDepartment of Inorganic Technology, University of Chemistry and Technology, Prague, Technická 5, 16628 Prague, Czech RepublicDepartment of Inorganic Technology, University of Chemistry and Technology, Prague, Technická 5, 16628 Prague, Czech RepublicDepartment of Chemistry, University of Patras, GR-26504 Patras, GreeceMechanically robust anion-exchange membranes (AEMs) with high conductivity and long-term alkali resistance are needed for water electrolysis application. In this work, aryl-ether free polyaromatics containing isatin moieties were prepared via super acid-catalyzed copolymerization, followed by functionalization with alkaline stable cyclic quaternary ammonium (QA) cationic groups, to afford high performance AEMs for application in water electrolysis. The incorporation of side functional cationic groups (pyrrolidinium and piperidinium) onto a polymer backbone via a flexible alkyl spacer aimed at conductivity and alkaline stability improvement. The effect of cation structure on the properties of prepared AEMs was thoroughly studied. Pyrrolidinium- and piperidinium-based AEMs showed similar electrolyte uptakes and no obvious phase separation, as revealed by SAXS and further supported by AFM and TEM data. In addition, these AEMs displayed high conductivity values (81. 5 and 120 mS cm<sup>−1</sup> for pyrrolidinium- and piperidinium-based AEM, respectively, at 80 °C) and excellent alkaline stability after 1 month aging in 2M KOH at 80 °C. Especially, a pyrrolidinium-based AEM membrane preserved 87% of its initial conductivity value, while at the same time retaining its flexibility and mechanical robustness after storage in alkaline media (2M KOH) for 1 month at 80 °C. Based on <sup>1</sup>H NMR data, the conductivity loss observed after the aging test is mainly related to the piperidinium degradation that took place, probably via ring-opening Hofmann elimination, alkyl spacer scission and nucleophilic substitution reactions as well. The synthesized AEMs were also tested in an alkaline water electrolysis cell. Piperidinium-based AEM showed superior performance compared to its pyrrolidinium analogue, owing to its higher conductivity as revealed by EIS data, further confirming the ex situ conductivity measurements.https://www.mdpi.com/2073-4360/16/1/99alkaline water electrolysisAEMsalkaline stabilitypiperidiniumpyrrolidiniumpoly(oxindole biphenyl) backbone |
| spellingShingle | Sara Gjoshi Paraskevi Loukopoulou Michaela Plevova Jaromir Hnat Karel Bouzek Valadoula Deimede Cycloaliphatic Quaternary Ammonium Functionalized Poly(oxindole biphenyl) Based Anion-Exchange Membranes for Water Electrolysis: Stability and Performance Polymers alkaline water electrolysis AEMs alkaline stability piperidinium pyrrolidinium poly(oxindole biphenyl) backbone |
| title | Cycloaliphatic Quaternary Ammonium Functionalized Poly(oxindole biphenyl) Based Anion-Exchange Membranes for Water Electrolysis: Stability and Performance |
| title_full | Cycloaliphatic Quaternary Ammonium Functionalized Poly(oxindole biphenyl) Based Anion-Exchange Membranes for Water Electrolysis: Stability and Performance |
| title_fullStr | Cycloaliphatic Quaternary Ammonium Functionalized Poly(oxindole biphenyl) Based Anion-Exchange Membranes for Water Electrolysis: Stability and Performance |
| title_full_unstemmed | Cycloaliphatic Quaternary Ammonium Functionalized Poly(oxindole biphenyl) Based Anion-Exchange Membranes for Water Electrolysis: Stability and Performance |
| title_short | Cycloaliphatic Quaternary Ammonium Functionalized Poly(oxindole biphenyl) Based Anion-Exchange Membranes for Water Electrolysis: Stability and Performance |
| title_sort | cycloaliphatic quaternary ammonium functionalized poly oxindole biphenyl based anion exchange membranes for water electrolysis stability and performance |
| topic | alkaline water electrolysis AEMs alkaline stability piperidinium pyrrolidinium poly(oxindole biphenyl) backbone |
| url | https://www.mdpi.com/2073-4360/16/1/99 |
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