Determination of Anion Transference Number and Phosphoric Acid Diffusion Coefficient in High Temperature Polymer Electrolyte Membranes

Hans Becker, Uwe Reimer, David Aili, Lars N. Cleemann, Jens Oluf Jensen, Werner Lehnert, Qingfeng Li*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

The passage of an electrical current through phosphoric acid doped polymer membranes involves parasitic migration of the acid, which imposes a critical issue for long-term operation of the high temperature polymer electrolyte membranes fuel cell (HT-PEMFC). To elucidate the phenomenon, a three-layered membrane is constructed with embedded micro reference electrodes to measure phosphoric acid redistribution in a polybenzimidazole based membrane. Under a constant load, a concentration gradient develops due to the acid migration, which drives the back diffusion of the acid and eventually reaches a steady state between migration and diffusion. The acid gradient is measured as a difference in local ohmic resistances of the anode- and cathode-layer membranes by electrochemical impedance spectroscopy. The phosphoric acid diffusion coefficient through the acid doped membrane is about 10(-11) m(2) s(-1), at least one order of magnitude lower than that of aqueous phosphoric acid solutions. The anion (H2PO4-) transference number is found to range up to 4% depending on current density, temperature and atmospheric humidity of the cell, implying that careful control of the operating parameters is needed in order to suppress the vehicular proton conduction as a degradation mitigation strategy. (C) The Author(s) 2018. Published by ECS.
Original languageEnglish
JournalJournal of the Electrochemical Society
Volume165
Issue number10
Pages (from-to)F863-F869
ISSN0013-4651
DOIs
Publication statusPublished - 2018

Bibliographical note

This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited.

Cite this

@article{7749c46903b04f108519a213411919bf,
title = "Determination of Anion Transference Number and Phosphoric Acid Diffusion Coefficient in High Temperature Polymer Electrolyte Membranes",
abstract = "The passage of an electrical current through phosphoric acid doped polymer membranes involves parasitic migration of the acid, which imposes a critical issue for long-term operation of the high temperature polymer electrolyte membranes fuel cell (HT-PEMFC). To elucidate the phenomenon, a three-layered membrane is constructed with embedded micro reference electrodes to measure phosphoric acid redistribution in a polybenzimidazole based membrane. Under a constant load, a concentration gradient develops due to the acid migration, which drives the back diffusion of the acid and eventually reaches a steady state between migration and diffusion. The acid gradient is measured as a difference in local ohmic resistances of the anode- and cathode-layer membranes by electrochemical impedance spectroscopy. The phosphoric acid diffusion coefficient through the acid doped membrane is about 10(-11) m(2) s(-1), at least one order of magnitude lower than that of aqueous phosphoric acid solutions. The anion (H2PO4-) transference number is found to range up to 4{\%} depending on current density, temperature and atmospheric humidity of the cell, implying that careful control of the operating parameters is needed in order to suppress the vehicular proton conduction as a degradation mitigation strategy. (C) The Author(s) 2018. Published by ECS.",
author = "Hans Becker and Uwe Reimer and David Aili and Cleemann, {Lars N.} and Jensen, {Jens Oluf} and Werner Lehnert and Qingfeng Li",
note = "This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited.",
year = "2018",
doi = "10.1149/2.1201810jes",
language = "English",
volume = "165",
pages = "F863--F869",
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issn = "0013-4651",
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Determination of Anion Transference Number and Phosphoric Acid Diffusion Coefficient in High Temperature Polymer Electrolyte Membranes. / Becker, Hans; Reimer, Uwe; Aili, David; Cleemann, Lars N.; Jensen, Jens Oluf; Lehnert, Werner; Li, Qingfeng.

In: Journal of the Electrochemical Society, Vol. 165, No. 10, 2018, p. F863-F869.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Determination of Anion Transference Number and Phosphoric Acid Diffusion Coefficient in High Temperature Polymer Electrolyte Membranes

AU - Becker, Hans

AU - Reimer, Uwe

AU - Aili, David

AU - Cleemann, Lars N.

AU - Jensen, Jens Oluf

AU - Lehnert, Werner

AU - Li, Qingfeng

N1 - This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited.

PY - 2018

Y1 - 2018

N2 - The passage of an electrical current through phosphoric acid doped polymer membranes involves parasitic migration of the acid, which imposes a critical issue for long-term operation of the high temperature polymer electrolyte membranes fuel cell (HT-PEMFC). To elucidate the phenomenon, a three-layered membrane is constructed with embedded micro reference electrodes to measure phosphoric acid redistribution in a polybenzimidazole based membrane. Under a constant load, a concentration gradient develops due to the acid migration, which drives the back diffusion of the acid and eventually reaches a steady state between migration and diffusion. The acid gradient is measured as a difference in local ohmic resistances of the anode- and cathode-layer membranes by electrochemical impedance spectroscopy. The phosphoric acid diffusion coefficient through the acid doped membrane is about 10(-11) m(2) s(-1), at least one order of magnitude lower than that of aqueous phosphoric acid solutions. The anion (H2PO4-) transference number is found to range up to 4% depending on current density, temperature and atmospheric humidity of the cell, implying that careful control of the operating parameters is needed in order to suppress the vehicular proton conduction as a degradation mitigation strategy. (C) The Author(s) 2018. Published by ECS.

AB - The passage of an electrical current through phosphoric acid doped polymer membranes involves parasitic migration of the acid, which imposes a critical issue for long-term operation of the high temperature polymer electrolyte membranes fuel cell (HT-PEMFC). To elucidate the phenomenon, a three-layered membrane is constructed with embedded micro reference electrodes to measure phosphoric acid redistribution in a polybenzimidazole based membrane. Under a constant load, a concentration gradient develops due to the acid migration, which drives the back diffusion of the acid and eventually reaches a steady state between migration and diffusion. The acid gradient is measured as a difference in local ohmic resistances of the anode- and cathode-layer membranes by electrochemical impedance spectroscopy. The phosphoric acid diffusion coefficient through the acid doped membrane is about 10(-11) m(2) s(-1), at least one order of magnitude lower than that of aqueous phosphoric acid solutions. The anion (H2PO4-) transference number is found to range up to 4% depending on current density, temperature and atmospheric humidity of the cell, implying that careful control of the operating parameters is needed in order to suppress the vehicular proton conduction as a degradation mitigation strategy. (C) The Author(s) 2018. Published by ECS.

U2 - 10.1149/2.1201810jes

DO - 10.1149/2.1201810jes

M3 - Journal article

VL - 165

SP - F863-F869

JO - Journal of The Electrochemical Society

JF - Journal of The Electrochemical Society

SN - 0013-4651

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