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Lookup NU author(s): Dr Hosni Ahmed Elwan Atout, Dr Corinne Wills, Professor Mohamed MamloukORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
Copyright © 2026. Published by Elsevier Ltd. Protic ionic liquids (PILs), prepared from a stoichiometric acid-base mixture, can function as electrolytes in proton exchange membrane fuel cells (PEMFCs) under low humidity. However, using platinum (Pt) microelectrode studies, we showed that in stoichiometric PILs, oxygen reduction (ORR) and hydrogen oxidation (HOR) kinetics are sluggish due to the lack of free protons for proton-transfer reactions. This can be addressed by adding excess acid to form non-stoichiometric PILs. In this work, we introduce new PILs: butyl pyrrolidinium triflate [Bu-Pyrr][TfO] and ethyl piperidinium triflate [Et-Pip][TfO], featuring thermally stable cations (boiling points: 155 °C and 131 °C). Adding 200 mM triflic acid enhanced Pt activity, yielding ORR currents of -7.17 and -3.08 mA/cm2 at 0 V vs. RHE, and HOR currents of 2.31 and 1.43 mA/cm2 at 0.75 V vs. RHE for [Bu-Pyrr][TfO] and [Et-Pip][TfO], respectively. ORR was limited by O2 solubility beyond 300 and 400 mM added acid for [Bu-Pyrr][TfO] and [Et-Pip][TfO], respectively, while HOR currents remained linearly dependent on added acid up to 500 mM. This study concludes that stoichiometric PILs are unsuitable for PEMFCs. Although non-stoichiometric PILs support electrochemical activity, cation adsorption on Pt increases overpotentials and reduces limiting currents; [Bu-Pyrr] raised ORR and HOR overpotentials by ∼10% and 6%, respectively.
Author(s): Elwan HA, Wills C, Mamlouk M
Publication type: Article
Publication status: Published
Journal: Electrochimica Acta
Year: 2026
Volume: 554
Print publication date: 01/04/2026
Online publication date: 16/01/2026
Acceptance date: 15/01/2026
Date deposited: 16/02/2026
ISSN (print): 0013-4686
ISSN (electronic): 1873-3859
Publisher: Elsevier Ltd
URL: https://doi.org/10.1016/j.electacta.2026.148231
DOI: 10.1016/j.electacta.2026.148231
Data Access Statement: Data will be made available on request.
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