Effects of hydrophobic side chains in poly(fluorenyl-<i>co</i>-aryl piperidinium) ionomers for durable anion exchange membrane fuel cells

Hu, Chuan; Park, Jong Hyeong; Kang, Na Yoon; Zhang, Xiaohua; Jeong, Sang Won; Lee, Young Moo

doi:10.1039/d2ta08726j

Cited by 30 publications

(12 citation statements)

References 41 publications

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“…One of the main conclusions was that AEMs with side chains attached to the backbone separated from the cationic groups were superior ion conductors in comparison with AEMs with side chains directly linked to the piperidinium cations. Lee and co-workers have directly compared the effects of having hexyl and octyl side chains, respectively, attached to either piperidinium cations or to fluorene units (Figure a) in the backbone . The study showed that side chains tethered to the cations reduced the alkaline stability and the conductivity, whereas the side chains placed on the fluorene units brought improved dimensional stability, ionic conductivity (up to 134 mS cm –1 ), mechanical properties and electrochemical stability.…”

Section: Aem For Use In Alkaline Solutions < 2 Mmentioning

confidence: 99%

“…Lee and co-workers have directly compared the effects of having hexyl and octyl side chains, respectively, attached to either piperidinium cations or to fluorene units (Figure 21a) in the backbone. 238 The study showed that side chains tethered to the cations reduced the alkaline stability and the conductivity, whereas the side chains placed on the fluorene units brought improved dimensional stability, ionic conductivity (up to 134 mS cm −1 ), mechanical properties and electrochemical stability. Li et al synthesized and investigated AEMs based on poly(arylene indole piperidinium) with different alkyl chains attached to the indole units (Figure 21b).…”

Section: Introduction Of Side Chainsmentioning

confidence: 99%

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Separators and Membranes for Advanced Alkaline Water Electrolysis

Henkensmeier,

Cho,

Jannasch

et al. 2024

Chem. Rev.

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Traditionally, alkaline water electrolysis (AWE) uses diaphragms to separate anode and cathode and is operated with 5−7 M KOH feed solutions. The ban of asbestos diaphragms led to the development of polymeric diaphragms, which are now the state of the art material. A promising alternative is the ion solvating membrane. Recent developments show that high conductivities can also be obtained in 1 M KOH. A third technology is based on anion exchange membranes (AEM); because these systems use 0−1 M KOH feed solutions to balance the trade-off between conductivity and the AEM's lifetime in alkaline environment, it makes sense to treat them separately as AEM WE. However, the lifetime of AEM increased strongly over the last 10 years, and some electrode-related issues like oxidation of the ionomer binder at the anode can be mitigated by using KOH feed solutions. Therefore, AWE and AEM WE may get more similar in the future, and this review focuses on the developments in polymeric diaphragms, ion solvating membranes, and AEM.

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Section: Aem For Use In Alkaline Solutions < 2 Mmentioning

confidence: 99%

Section: Introduction Of Side Chainsmentioning

confidence: 99%

Separators and Membranes for Advanced Alkaline Water Electrolysis

Henkensmeier,

Cho,

Jannasch

et al. 2024

Chem. Rev.

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“…Anode flooding increased the mass transfer resistance of hydrogen, causing voltage loss, while cathode dry-out increased the nucleophilicity of hydroxide ions to attack the functional groups, resulting in degradation of ionomers and an increase in ohmic resistance. Kim, Mustain, and co-workers revealed that the water environment in fuel cells can be optimized by controlling the relative humidity (RH), gas flow rate, and polarity of ionomers in the cathode and anode. − ,− …”

Section: Introductionmentioning

confidence: 99%

“…Dekel and co-workers pointed out that the improved hydroxide conductivity of AEM enhanced water diffusion through the membrane, which is critical for long-term operation of AEMFCs . In addition, inappropriate operation conditions also cause the limited fuel cell performance and durability of AMEFCs. − As has been well elucidated, the water environment of AEMFCs is much more complicated than that of PEMFCs, ,, and the severe water imbalance caused by the water generation reaction in the anode and the water consumption reaction in the cathode can accelerate the degradation of fuel cells . Moreover, the transport of OH – ions from the cathode to the anode accompanied by 8 water molecules further exacerbated the imbalance of water distributions .…”

Section: Introductionmentioning

confidence: 99%

Stabilizing the Catalyst Layer for Durable and High Performance Alkaline Membrane Fuel Cells and Water Electrolyzers

Hu,

Kang,

Jung

et al. 2024

ACS Cent. Sci.

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Anion exchange membrane (AEM) fuel cells (AEMFCs) and water electrolyzers (AEMWEs) suffer from insufficient performance and durability compared with commercialized energy conversion systems. Great efforts have been devoted to designing high-quality AEMs and catalysts. However, the significance of the stability of the catalyst layer has been largely disregarded. Here, an in situ cross-linking strategy was developed to promote the interactions within the catalyst layer and the interactions between catalyst layer and AEM. The adhesion strength of the catalyst layer after cross-linking was improved 7 times compared with the uncross-linked catalyst layer due to the formation of covalent bonds between the catalyst layer and AEM. The AEMFC can be operated under 0.6 A cm −2 for 1000 h with a voltage decay rate of 20 μV h −1 . The related AEMWE achieved an unprecedented current density of 15.17 A cm −2 at 2.0 V and was operated at 0.5, 1.0, and 1.5 A cm −2 for 1000 h.

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“…Because of their high ionic conductivity and evident microphase separation, the prepared AEMs can reach a maximum power density of 785.6 mW cm −2 . Hu et al 31 reported a set of AEMs with varying lengths of hydrophobic side chains located at different graft positions. Because of the apparent microphase separation, the obtained AEMs had an ionic conductivity of 143.2 mS cm −1 and a peak power density (PPD) of 2.6 W cm −2 .…”

Section: Introductionmentioning

confidence: 99%

Modification of Hydrophobic Diacid Units for Enhanced Poly(crown ether) Anion-Exchange Membrane Performance

Chen,

Lai,

Choo

et al. 2023

ACS Appl. Energy Mater.

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Ideal anion-exchange membranes (AEMs) for anion-exchange membrane fuel cells (AEMFCs) must possess high OH − conductivity, excellent alkaline resistance, good thermal stability, and improved dimensional stability. In this study, four types of poly(crown ether) (PCE) cross-linked AEMs containing different aromatic or alicyclic dicarboxylic acids were prepared for AEMFCs. The hydrophilic/hydrophobic polarity discrimination of AEMs can be adjusted by the introduction of various diacids into the polymer backbones. As a result, an obvious microphase-separated structure will form in AEMs, which may aid the movement of hydroxide ions. The as-prepared QAPCE-1.4P membranes with 1,4-phenylenediacetic acid as the dicarboxylic acid exhibit a distinct micromorphology separation, as confirmed by morphology characterization using small-angle X-ray scattering, atomic force microscopy, as well as transmission electron microscopy. The highest hydroxide ion conductivity of QAPCE-1.4P at 80 °C in ultrapure water is 133.25 mS cm −1 . Meanwhile, QAPCE-1.4P shows an improved dimensional stability at 80 °C with a swelling ratio of 10.83%. In addition, QAPCE-1.4P shows good chemical stability (96.1% ionic conductivity retention) even after being put in harsh alkali conditions at 80 °C for 40 days. Furthermore, the maximum power density of a single cell using QAPCE-1.4P as the polymer electrolyte membranes can reach 689 mW cm −2 in hydrogen/oxygen (80 °C).

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Effects of hydrophobic side chains in poly(fluorenyl-co-aryl piperidinium) ionomers for durable anion exchange membrane fuel cells

Abstract: Durable and conductive catalyst layers are critical for anion exchange membrane fuel cells (AEMFCs) to achieve high power density and sufficient lifespan. Great efforts have been devoted to improving the...

Cited by 30 publications

References 41 publications

Separators and Membranes for Advanced Alkaline Water Electrolysis

Separators and Membranes for Advanced Alkaline Water Electrolysis

Stabilizing the Catalyst Layer for Durable and High Performance Alkaline Membrane Fuel Cells and Water Electrolyzers

Modification of Hydrophobic Diacid Units for Enhanced Poly(crown ether) Anion-Exchange Membrane Performance

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