Nanometer-Scale Water Dynamics in Nafion Polymer Electrolyte Membranes: Influence of Molecular Hydrophobicity and Water Content Revisited

Seung Bo Saun; Jiwon Kim; Ryeo Yun Hwang; Yeonho Ahn; Dukjoon Kim; Daniel K. Park; Soonchil Lee; Oc Hee Han

doi:10.1021/acsmacrolett.0c00173

Nanometer-Scale Water Dynamics in Nafion Polymer Electrolyte Membranes: Influence of Molecular Hydrophobicity and Water Content Revisited

Seung Bo Saun, Jiwon Kim, Ryeo Yun Hwang, Yeonho Ahn, Dukjoon Kim, Daniel K. Park, Soonchil Lee, Oc Hee Han

Department of Applied Statistics

Research output: Contribution to journal › Article › peer-review

2 Citations (Scopus)

Abstract

The ionic conductivity of polymer electrolyte membranes (PEMs) is an essential parameter for their device applications. In water-swollen PEMs, protons and other ions are transferred through hydrophilic channels of a few nanometers in diameter at most. Thus, optimizing the chemical and physical properties of the channels can enhance the conductivity of PEMs. However, the factors controlling the conductivity have not been completely clarified. Here, we report that measurements taken near the channel walls by a special nuclear magnetic resonance technique with ≤1 nm spatial resolution showed the largest water diffusivity when ∼80% of hydrophilic sulfonic acid groups were blocked, but the proton conductivity was low. The water diffusivity was much less affected by differences in water content. Our results provide a concept for changing the properties of PEMs and a challenge to implement the improved diffusivity in a way that enhances net ion conductivity.

Original language	English
Pages (from-to)	1013-1018
Number of pages	6
Journal	ACS Macro Letters
Volume	9
Issue number	7
DOIs	https://doi.org/10.1021/acsmacrolett.0c00173
Publication status	Published - 2020 Jul 21

Bibliographical note

Funding Information:
This work was supported by the Grant (DRC-14-1-KBSI) of the National Research Council of Science and Technology in Korea to O.H.H., by Ministry of Science, the Grant (C39925) of the KBSI, and Technology Development Program to Solve Climate Changes (NRF-2018M1A2A2063349) through the National Research Foundation of Korea. We thank Dr. SangGap Lee at the Korea Basic Science Institute for the generous loan of an NMR console and informative discussion during the initial construction of a NMR system for the ODNP-NMR system.

Publisher Copyright:
Copyright © 2020 American Chemical Society.

All Science Journal Classification (ASJC) codes

Organic Chemistry
Polymers and Plastics
Inorganic Chemistry
Materials Chemistry

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10.1021/acsmacrolett.0c00173

Cite this

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title = "Nanometer-Scale Water Dynamics in Nafion Polymer Electrolyte Membranes: Influence of Molecular Hydrophobicity and Water Content Revisited",

abstract = "The ionic conductivity of polymer electrolyte membranes (PEMs) is an essential parameter for their device applications. In water-swollen PEMs, protons and other ions are transferred through hydrophilic channels of a few nanometers in diameter at most. Thus, optimizing the chemical and physical properties of the channels can enhance the conductivity of PEMs. However, the factors controlling the conductivity have not been completely clarified. Here, we report that measurements taken near the channel walls by a special nuclear magnetic resonance technique with ≤1 nm spatial resolution showed the largest water diffusivity when ∼80% of hydrophilic sulfonic acid groups were blocked, but the proton conductivity was low. The water diffusivity was much less affected by differences in water content. Our results provide a concept for changing the properties of PEMs and a challenge to implement the improved diffusivity in a way that enhances net ion conductivity.",

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note = "Funding Information: This work was supported by the Grant (DRC-14-1-KBSI) of the National Research Council of Science and Technology in Korea to O.H.H., by Ministry of Science, the Grant (C39925) of the KBSI, and Technology Development Program to Solve Climate Changes (NRF-2018M1A2A2063349) through the National Research Foundation of Korea. We thank Dr. SangGap Lee at the Korea Basic Science Institute for the generous loan of an NMR console and informative discussion during the initial construction of a NMR system for the ODNP-NMR system. Publisher Copyright: Copyright {\textcopyright} 2020 American Chemical Society.",

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AU - Park, Daniel K.

AU - Lee, Soonchil

AU - Han, Oc Hee

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PY - 2020/7/21

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N2 - The ionic conductivity of polymer electrolyte membranes (PEMs) is an essential parameter for their device applications. In water-swollen PEMs, protons and other ions are transferred through hydrophilic channels of a few nanometers in diameter at most. Thus, optimizing the chemical and physical properties of the channels can enhance the conductivity of PEMs. However, the factors controlling the conductivity have not been completely clarified. Here, we report that measurements taken near the channel walls by a special nuclear magnetic resonance technique with ≤1 nm spatial resolution showed the largest water diffusivity when ∼80% of hydrophilic sulfonic acid groups were blocked, but the proton conductivity was low. The water diffusivity was much less affected by differences in water content. Our results provide a concept for changing the properties of PEMs and a challenge to implement the improved diffusivity in a way that enhances net ion conductivity.

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Nanometer-Scale Water Dynamics in Nafion Polymer Electrolyte Membranes: Influence of Molecular Hydrophobicity and Water Content Revisited

Abstract

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