Alkali-stable polybenzimidazole anion exchange membranes tethered with <i>N</i>,<i>N</i>-dimethylpiperidinium cations for dilute aqueous KOH fed water electrolyzers

Boström, Oskar; Choi, Seung-Young; Xia, Lu; Meital, Shviro; Lohmann-Richters, Felix; Jannasch, Patric

doi:10.1039/d3ta03216g

Cited by 14 publications

(4 citation statements)

References 43 publications

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“…The decreasing electrolyte uptake with increasing KOH concentration has also been observed in other membrane systems based on sulfonated polymers . This phenomenon has also been observed in anion exchange membrane systems, where it has been described as a consequence of the breakdown of the Donnan exclusion, which results in sorption of concentrated electrolyte and shrinking of the hydrophilic domains …”

Section: Results and Discussionmentioning

confidence: 76%

“…36 This phenomenon has also been observed in anion exchange membrane systems, where it has been described as a consequence of the breakdown of the Donnan exclusion, which results in sorption of concentrated electrolyte and shrinking of the hydrophilic domains. 37 The weight fractions of KOH, water, and polymer of the membranes based on S4-M, S4-M s , S5-M, and S5-M s after equilibration in 10−25 wt % KOH are shown in Figures 5a, 5b, 5c, and 5d, respectively. For the S4-M and S4-M s membranes, the KOH fraction remained relatively stable at 5 wt % regardless of the concentration of the surrounding solution.…”

Section: Electrolyte Uptake and Morphologymentioning

confidence: 99%

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Carboxylated Polystyrene-b-poly(ethylene-ran-butylene)-b-polystyrene Membranes for Alkaline Water Electrolysis

Serhiichuk,

Tian,

Almind

et al. 2024

ACS Appl. Energy Mater.

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A series of membranes based on carboxylated polystyrene-b-poly(ethylene-ran-butylene)-b-polystyrene (SEBS) were synthesized via Friedel−Crafts bromoalkylation, substitution with malonate esters, and heterogeneous ester hydrolysis. The physicochemical properties of the obtained membranes, including electrolyte uptake, swelling ratio, and ionic conductivity, were highly affected by the degree of functionalization and the concentration of the aqueous KOH solution. Membranes with degrees of functionalization higher than 100% suffered from excessive swelling and poor mechanical stability. However, membranes with degrees of functionalization in the range of 50−75% combined high electrolyte uptake and ion conductivity with mechanical robustness. The area specific resistance during electrolysis testing in 15 wt % aqueous KOH at 80 °C was 0.18 Ω cm 2 after 1 week, with no signs of degradation. The H 2 in the O 2 level at 50 mA cm −2 was about 0.5%, which was considerably lower than that of Zirfon despite being four times thinner.

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Section: Results and Discussionmentioning

confidence: 76%

Section: Electrolyte Uptake and Morphologymentioning

confidence: 99%

Carboxylated Polystyrene-b-poly(ethylene-ran-butylene)-b-polystyrene Membranes for Alkaline Water Electrolysis

Serhiichuk,

Tian,

Almind

et al. 2024

ACS Appl. Energy Mater.

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“…However, very recently, polybenzimidazole tethered with N , N -dimethylpiperidinium cations was reported for use in dilute aqueous KOH-fed electrolyzers. The conductivity of the prepared membranes reached values ranging from 19 to 38 mS cm −1 in 2M KOH at 80 °C [ 46 ].…”

Section: Resultsmentioning

confidence: 99%

“…Two sets of vinylic signals (small signals) emerged in the region between 4.8 ppm and 5.8 ppm after 2 weeks’ alkaline treatment, and their intensity slightly increased with increasing aging time (after 1 month). The first set of signals observed (at ~4.9 and ~5.8 ppm, corresponding to CH 2 = and CH -CH 2 , respectively) strongly implies that Hofmann β-elimination degradation of the piperidinium ring took place, while the second set of signals (at ~4.8 and ~5.7ppm, assigned to CH 2 = and CH -CH 2 , respectively) is attributed then to β-elimination in the alkyl spacer chain [ 27 , 46 , 49 , 50 ]. In addition, two different signals from protonated amines were detected at ∼9.2 and ∼9.0 ppm, respectively, where the former is ascribed to ring-opening β-elimination and the latter was consequently attributed to nucleophilic substitution at the methyl position of the piperidinium ring [ 51 ].…”

Section: Resultsmentioning

confidence: 99%

Cycloaliphatic Quaternary Ammonium Functionalized Poly(oxindole biphenyl) Based Anion-Exchange Membranes for Water Electrolysis: Stability and Performance

Gjoshi,

Loukopoulou,

Plevova

et al. 2023

Polymers

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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−1 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 1H 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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Tuning the Performance of Poly(quaterphenyl piperidinium) Anion‐Exchange Membranes by Monomer Configuration

Bakvand,

Pan,

Allushi

et al. 2024

Advanced Energy Materials

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Poly(arylene piperidinium)s are attractive anion exchange membranes (AEMs) for alkaline membrane fuel cells and water electrolyzers because of their high chemical stability and hydroxide conductivity. Here, ether‐ and fluorine‐free hydroxide conducting poly(quaterphenyl piperidinium) membranes with very similar ion exchange capacity (IEC), but different ratios of meta to para connectivity in the quaterphenyl units, are synthesized and explored. Ionic clustering, water uptake, and the hydroxide conductivity of the AEMs increase gradually with increasing backbone flexibility, i.e., the fraction of meta connectivity. At 80 °C, the AEMs with para,para‐ and meta,meta‐quaterphenyl units, respectively, reach a conductivity of 96 and 178 mS cm−1, respectively, at a water uptake of 37 and 209%, respectively. Alkaline stability evaluations reveal high alkaline stability, increasing with backbone flexibility. Under very harsh conditions, the cationic loss increases with chain stiffness and occurs mainly through Hofmann β‐elimination, but also increasingly via nucleophilic methyl substitution. Copolymerization of quaterphenyls provides properties in between the corresponding homopolymers. In conclusion, it is demonstrated that the configuration of the quaterphenyl monomer can be efficiently tailored to manipulate the chain flexibility of highly alkali‐stable AEMs for control over the water uptake and ionic conductivity in a wide range without changing the ionic content of the membranes.

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Alkali-stable polybenzimidazole anion exchange membranes tethered with N,N-dimethylpiperidinium cations for dilute aqueous KOH fed water electrolyzers

Abstract: Polybenzimidazole (PBI) is currently considered as a membrane material for alkaline water electrolyzers (AWEs), and has to be fed with highly concentrated aqueous KOH electrolytes in order to ensure sufficient...

Cited by 14 publications

References 43 publications

Carboxylated Polystyrene-b-poly(ethylene-ran-butylene)-b-polystyrene Membranes for Alkaline Water Electrolysis

Carboxylated Polystyrene-b-poly(ethylene-ran-butylene)-b-polystyrene Membranes for Alkaline Water Electrolysis

Cycloaliphatic Quaternary Ammonium Functionalized Poly(oxindole biphenyl) Based Anion-Exchange Membranes for Water Electrolysis: Stability and Performance

Tuning the Performance of Poly(quaterphenyl piperidinium) Anion‐Exchange Membranes by Monomer Configuration

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