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Proton exchange membranes with perfluorobenzenesulfonic acid groups for vanadium redox flow battery applications

Xue, Xiaoting LU ; Lv, Peiru ; Yang, Jingshuai LU and Jannasch, Patric LU orcid (2026) In Journal of Materials Chemistry A
Abstract

Proton exchange membranes (PEMs) are critical to the performance of vanadium redox flow batteries (VRFBs). Still, conventional perfluorosulfonic acid membranes such as Nafion® suffer from poor ion selectivity and limited long-term stability. In this study, we introduce PEMs prepared from four types of poly(arylene perfluorobenzenesulfonic acid)s, synthesized via polyhydroxyalkylations of biphenyl (BP) or p-terphenyl (TP) with pentafluorobenzaldehyde (BA) or perfluoroacetophenone (AP), named according to their monomer contents (e.g., sBPBA). The combination of rigid, ether-free polymer backbones and the densely distributed highly acidic sulfonic acid groups... (More)

Proton exchange membranes (PEMs) are critical to the performance of vanadium redox flow batteries (VRFBs). Still, conventional perfluorosulfonic acid membranes such as Nafion® suffer from poor ion selectivity and limited long-term stability. In this study, we introduce PEMs prepared from four types of poly(arylene perfluorobenzenesulfonic acid)s, synthesized via polyhydroxyalkylations of biphenyl (BP) or p-terphenyl (TP) with pentafluorobenzaldehyde (BA) or perfluoroacetophenone (AP), named according to their monomer contents (e.g., sBPBA). The combination of rigid, ether-free polymer backbones and the densely distributed highly acidic sulfonic acid groups led to high proton conductivity and improved ion selectivity. In addition, the –CF3 substitution in the PEMs derived from perfluoroacetophenone likely increased the free volume and enhanced chemical stability. These membranes displayed reduced area resistance and markedly lower vanadium ion permeability compared to Nafion®115. In VRFB single-cell tests, the membranes sBPBA, sTPBA, and sBPAP consistently delivered higher voltage and energy efficiencies than Nafion®115 across 40–160 mA cm⁻2, with the former PEM achieving the highest energy efficiency at all current densities. Long-term cycling demonstrated outstanding stability for sBPAP (~99.5% CE, ~82% EE over 450 cycles), moderate stability for sTPAP (~98% CE over 250 cycles), and rapid performance degradation for sBPBA and sTPBA, prepared from pentafluorobenzaldehyde. This study demonstrates that CF3-containing poly(arylene perfluorophenyl) PEMs, which contain only a small fraction of the perfluoroalkyl (PFAS) content found in Nafion®, are promising candidates for high-efficiency, durable VRFB operation. It also provides a clear molecular design framework for developing advanced membrane materials.

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Please use this url to cite or link to this publication:
author
; ; and
organization
publishing date
type
Contribution to journal
publication status
epub
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in
Journal of Materials Chemistry A
publisher
Royal Society of Chemistry
ISSN
2050-7488
DOI
10.1039/D5TA08577B
language
English
LU publication?
yes
id
1d6ee615-246e-4ac6-b587-ccf606853a48
date added to LUP
2025-08-29 11:40:26
date last changed
2026-02-05 10:46:23
@article{1d6ee615-246e-4ac6-b587-ccf606853a48,
  abstract     = {{<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph">Proton exchange membranes (PEMs) are critical to the performance of vanadium redox flow batteries (VRFBs). Still, conventional perfluorosulfonic acid membranes such as Nafion® suffer from poor ion selectivity and limited long-term stability. In this study, we introduce PEMs prepared from four types of poly(arylene perfluorobenzenesulfonic acid)s, synthesized via polyhydroxyalkylations of biphenyl (BP) or <i>p</i>-terphenyl (TP) with pentafluorobenzaldehyde (BA) or perfluoroacetophenone (AP), named according to their monomer contents (e.g., sBPBA). The combination of rigid, ether-free polymer backbones and the densely distributed highly acidic sulfonic acid groups led to high proton conductivity and improved ion selectivity. In addition, the –CF<sub>3</sub> substitution in the PEMs derived from perfluoroacetophenone likely increased the free volume and enhanced chemical stability. These membranes displayed reduced area resistance and markedly lower vanadium ion permeability compared to Nafion®115. In VRFB single-cell tests, the membranes sBPBA, sTPBA, and sBPAP consistently delivered higher voltage and energy efficiencies than Nafion®115 across 40–160 mA cm⁻<sup>2</sup>, with the former PEM achieving the highest energy efficiency at all current densities. Long-term cycling demonstrated outstanding stability for sBPAP (~99.5% CE, ~82% EE over 450 cycles), moderate stability for sTPAP (~98% CE over 250 cycles), and rapid performance degradation for sBPBA and sTPBA, prepared from pentafluorobenzaldehyde. This study demonstrates that CF<sub>3</sub>-containing poly(arylene perfluorophenyl) PEMs, which contain only a small fraction of the perfluoroalkyl (PFAS) content found in Nafion®, are promising candidates for high-efficiency, durable VRFB operation. It also provides a clear molecular design framework for developing advanced membrane materials.</p><p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"/>}},
  author       = {{Xue, Xiaoting and Lv, Peiru and Yang, Jingshuai and Jannasch, Patric}},
  issn         = {{2050-7488}},
  language     = {{eng}},
  publisher    = {{Royal Society of Chemistry}},
  series       = {{Journal of Materials Chemistry A}},
  title        = {{Proton exchange membranes with perfluorobenzenesulfonic acid groups for vanadium redox flow battery applications}},
  url          = {{http://dx.doi.org/10.1039/D5TA08577B}},
  doi          = {{10.1039/D5TA08577B}},
  year         = {{2026}},
}