Hydrogen mass transport resistance changes in a high temperature polymer membrane fuel cell as a function of current density and acid doping

Sobi Thomas*, Samuel Simon Araya, Steffen Henrik Frensch, Thomas Steenberg, Søren Knudsen Kær

*Corresponding author

Research output: Contribution to journalJournal articleResearchpeer-review

2 Citations (Scopus)

Abstract

High temperature polymer electrolyte membrane fuel cells (HT-PEMFC) have phosphoric acid doped membranes. Acid in the membrane is mobile and tends to move out of the membrane depending on the acid doping. The migration of acid (when the doping is high) towards the anode at high current density >0.4Acm−2 causes gas diffusion layer (GDL) and catalyst flooding which thereby results higher hydrogen transport resistance. Thus, it is important to determine the acid doping level, which is optimal. In this study, transient changes in hydrogen mass transport is investigated as a function of doping level and current density. Three doping levels 11, 8.3 and 7 molecules of H2PO4 per PBI repeat unit are investigated. Electrochemical impedance spectroscopy (EIS) was modified to a single frequency measurement and time constant are calculated for resistance change with current density using a linear fit. The time constants are 2.0 ± 0.5, 3.4 ± 0.3, 8.2 ± 0.2 min for low and 2.5 ± 0.8, 4.9 ± 0.3 and 4.5 ± 0.2 min for high current densities, for the respective doping levels. The resistance decreases at high and increases at low current densities for all the doping levels with a varying time constant. This change in time constant is attributed to low doping level having lower capillary pressure to push the acid from reaching GDL pores from the membrane and/or catalyst layer.
Original languageEnglish
JournalElectrochimica Acta
Volume317
Pages (from-to)521-527
Number of pages7
ISSN0013-4686
DOIs
Publication statusPublished - Sep 2019

Fingerprint

Fuel cells
Hydrogen
Polymers
Current density
Mass transfer
Doping (additives)
Membranes
Acids
Temperature
Diffusion in gases
Catalysts
Capillarity
Phosphoric acid
Proton exchange membrane fuel cells (PEMFC)
Electrochemical impedance spectroscopy
Anodes
Molecules

Keywords

  • EIS
  • Fuel cell
  • High temperature PEM
  • Load cycling
  • Phosphoric acid

Cite this

@article{b2223f4ce8254e30ada60161e3f76a83,
title = "Hydrogen mass transport resistance changes in a high temperature polymer membrane fuel cell as a function of current density and acid doping",
abstract = "High temperature polymer electrolyte membrane fuel cells (HT-PEMFC) have phosphoric acid doped membranes. Acid in the membrane is mobile and tends to move out of the membrane depending on the acid doping. The migration of acid (when the doping is high) towards the anode at high current density >0.4Acm−2 causes gas diffusion layer (GDL) and catalyst flooding which thereby results higher hydrogen transport resistance. Thus, it is important to determine the acid doping level, which is optimal. In this study, transient changes in hydrogen mass transport is investigated as a function of doping level and current density. Three doping levels 11, 8.3 and 7 molecules of H2PO4 per PBI repeat unit are investigated. Electrochemical impedance spectroscopy (EIS) was modified to a single frequency measurement and time constant are calculated for resistance change with current density using a linear fit. The time constants are 2.0 ± 0.5, 3.4 ± 0.3, 8.2 ± 0.2 min for low and 2.5 ± 0.8, 4.9 ± 0.3 and 4.5 ± 0.2 min for high current densities, for the respective doping levels. The resistance decreases at high and increases at low current densities for all the doping levels with a varying time constant. This change in time constant is attributed to low doping level having lower capillary pressure to push the acid from reaching GDL pores from the membrane and/or catalyst layer.",
keywords = "EIS, Fuel cell, High temperature PEM, Load cycling, Phosphoric acid",
author = "Sobi Thomas and Araya, {Samuel Simon} and Frensch, {Steffen Henrik} and Thomas Steenberg and K{\ae}r, {S{\o}ren Knudsen}",
year = "2019",
month = "9",
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language = "English",
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journal = "Electrochimica Acta",
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Hydrogen mass transport resistance changes in a high temperature polymer membrane fuel cell as a function of current density and acid doping. / Thomas, Sobi; Araya, Samuel Simon; Frensch, Steffen Henrik; Steenberg, Thomas; Kær, Søren Knudsen.

In: Electrochimica Acta, Vol. 317, 09.2019, p. 521-527.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Hydrogen mass transport resistance changes in a high temperature polymer membrane fuel cell as a function of current density and acid doping

AU - Thomas, Sobi

AU - Araya, Samuel Simon

AU - Frensch, Steffen Henrik

AU - Steenberg, Thomas

AU - Kær, Søren Knudsen

PY - 2019/9

Y1 - 2019/9

N2 - High temperature polymer electrolyte membrane fuel cells (HT-PEMFC) have phosphoric acid doped membranes. Acid in the membrane is mobile and tends to move out of the membrane depending on the acid doping. The migration of acid (when the doping is high) towards the anode at high current density >0.4Acm−2 causes gas diffusion layer (GDL) and catalyst flooding which thereby results higher hydrogen transport resistance. Thus, it is important to determine the acid doping level, which is optimal. In this study, transient changes in hydrogen mass transport is investigated as a function of doping level and current density. Three doping levels 11, 8.3 and 7 molecules of H2PO4 per PBI repeat unit are investigated. Electrochemical impedance spectroscopy (EIS) was modified to a single frequency measurement and time constant are calculated for resistance change with current density using a linear fit. The time constants are 2.0 ± 0.5, 3.4 ± 0.3, 8.2 ± 0.2 min for low and 2.5 ± 0.8, 4.9 ± 0.3 and 4.5 ± 0.2 min for high current densities, for the respective doping levels. The resistance decreases at high and increases at low current densities for all the doping levels with a varying time constant. This change in time constant is attributed to low doping level having lower capillary pressure to push the acid from reaching GDL pores from the membrane and/or catalyst layer.

AB - High temperature polymer electrolyte membrane fuel cells (HT-PEMFC) have phosphoric acid doped membranes. Acid in the membrane is mobile and tends to move out of the membrane depending on the acid doping. The migration of acid (when the doping is high) towards the anode at high current density >0.4Acm−2 causes gas diffusion layer (GDL) and catalyst flooding which thereby results higher hydrogen transport resistance. Thus, it is important to determine the acid doping level, which is optimal. In this study, transient changes in hydrogen mass transport is investigated as a function of doping level and current density. Three doping levels 11, 8.3 and 7 molecules of H2PO4 per PBI repeat unit are investigated. Electrochemical impedance spectroscopy (EIS) was modified to a single frequency measurement and time constant are calculated for resistance change with current density using a linear fit. The time constants are 2.0 ± 0.5, 3.4 ± 0.3, 8.2 ± 0.2 min for low and 2.5 ± 0.8, 4.9 ± 0.3 and 4.5 ± 0.2 min for high current densities, for the respective doping levels. The resistance decreases at high and increases at low current densities for all the doping levels with a varying time constant. This change in time constant is attributed to low doping level having lower capillary pressure to push the acid from reaching GDL pores from the membrane and/or catalyst layer.

KW - EIS

KW - Fuel cell

KW - High temperature PEM

KW - Load cycling

KW - Phosphoric acid

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DO - 10.1016/j.electacta.2019.06.021

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SP - 521

EP - 527

JO - Electrochimica Acta

JF - Electrochimica Acta

SN - 0013-4686

ER -