Understanding the hydrocarbon – PFSA ionomer conductivity gap in hydrogen fuel cells

Bangay, W., Yandrasits, M. and Hayes, W. ORCID: https://orcid.org/0000-0003-0047-2991 (2025) Understanding the hydrocarbon – PFSA ionomer conductivity gap in hydrogen fuel cells. Physical Chemistry Chemical Physics, 27 (16). pp. 8305-8319. ISSN 1463-9076 doi: 10.1039/d5cp00334b

Abstract/Summary

Hydrocarbon ionomers (HCs) have the potential to replace perfluorinated sulfonic acids (PFSAs), which are currently used in electrolyser or fuel cell membranes. To be a truly viable alternative, HCs must have conductivity across the operating range and cell lifetime comparable to PFSAs. Conductivity is an important property of membranes because it affects the energy efficiency of a fuel cell or electrolyser. By examining conductivity as a function of water volume fraction, it becomes evident that HC ionomers have consistently lower conductivity at low relative humidity. To better understand this ‘conductivity gap’, conductivity was converted to proton diffusivity and analysed using General Effective Media (GEM) theory for the first time. This analysis revealed that all ionomers require similar hydration levels for proton dissociation, and proton diffusion coefficients in the dry polymer are responsible for the conductivity gap. It is suggested that the membrane tortuosity ultimately accounts for the dry membrane’s proton diffusivity and low RH conductivity. As the membrane hydrates however, all ionomers exhibit similar diffusion coefficients, indicating that conductivity at high humidity is limited by proton concentration.

Item Type	Article
URI	https://centaur.reading.ac.uk/id/eprint/122805
Identification Number/DOI	10.1039/d5cp00334b
Refereed	Yes
Divisions	Life Sciences > School of Chemistry, Food and Pharmacy > Department of Chemistry
Publisher	Royal Society of Chemistry
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