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Investigation of mass transport in gas diffusion layer at the air cathode of a PEMFC
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
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2005 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 51, no 3, p. 474-488Article in journal (Refereed) Published
Abstract [en]

In a polymer electrolyte membrane fuel cell (PEMFC), slowdiffusion in the gas diffusion electrode may induce oxygen depletion when using air at the cathode. This work focuses on the behavior of a single PEMFC built with a Nafion® based MEA and an E-TEK gas diffusion layer and fed at the cathode with nitrogen containing 5, 10 and 20% of oxygen and working at different cell temperatures and relative humidities. The purpose is to apply the experimental impedance technique to cells wherein transport limitations at the cathode are significant. In parallel, a model is proposed to interpret the polarization curves and the impedance diagrams of a single PEMFC. The model accounts for mass transport through the gas diffusion electrode. It allows us to qualitatively analyze the experimental polarization curves and the corresponding impedance spectra and highlights the intra-electrode processes and the influence of the gas diffusion layer.

Place, publisher, year, edition, pages
2005. Vol. 51, no 3, p. 474-488
Keywords [en]
Gas diffusion layer, Impedance, Mass transport, Modeling, PEMFC
National Category
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-10098DOI: 10.1016/j.electacta.2005.05.007ISI: 000233226100012Scopus ID: 2-s2.0-26844505918OAI: oai:DiVA.org:kth-10098DiVA, id: diva2:208232
Note
QC 20101104Available from: 2009-03-16 Created: 2009-03-16 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Modelling and Experimental Investigation of the Dynamics in Polymer Electrolyte Fuel Cells
Open this publication in new window or tab >>Modelling and Experimental Investigation of the Dynamics in Polymer Electrolyte Fuel Cells
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In polymer electrolyte fuel cells (PEFC) chemical energy, in for example hydrogen, is converted by an electrochemical process into electrical energy. The PEFC has a working temperature generally below 100 °C. Under these conditions water management and transport of oxygen to the cathode are the parameters limiting the performance of the PEFC.

The purpose of this thesis was to better understand the complex processes in different parts of the PEFC. The rate-limiting processes in the cathode were studied using pure oxygen while varying oxygen pressure and humidity. Mass-transport limitations in the gas diffusion layer using oxygen diluted in nitrogen or helium was also studied. A large capacitive loop was seen at 1-10 Hz with 5-20 % oxygen. When nitrogen was changed to helium, which has a higher binary diffusion coefficient, the loop decreased and shifted to a higher frequency.

Steady-state and electrochemical impedance spectroscopy (EIS) models have been developed that accounts for water transport in the membrane and the influence of water on the anode. Due to water drag, the membrane resistance changes with current density. This gives rise to a low frequency loop in the complex plane plot. The loop appeared at a frequency of around 0.1 Hz and varied with D/Lm2, where D is the water diffusion coefficient and Lm is the membrane thickness. The EIS model for the hydrogen electrode gave three to four semicircles in the complex plane plot when taking the influence of water concentration on the anode conductivity and kinetics into account. The high-frequency semicircle is attributed to the Volmer reaction, the medium-frequency semicircle to the pseudocapacitance resulting from the adsorbed hydrogen, and the low-frequency semicircles to variations in electrode performance with water concentration. These low-frequency semicircles appear in a frequency range overlapping with the low-frequency semicircles from the water transport in the membrane. The effects of current density and membrane thickness were studied experimentally. An expected shift in frequency, when varying the membrane thickness was seen. This shift confirms the theory that the low-frequency loop is connected to the water transport in the membrane.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2009. p. 46
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2009:6
Keywords
polymer electrolyte fuel cell, modelling, electrochemical impedance spectroscopy, water transport, membrane
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-10087 (URN)978-91-7415-241-8 (ISBN)
Presentation
2009-04-03, D2, Lindstedtsvägen 5, KTH, Stockholm, 10:15 (Swedish)
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Supervisors
Note

QC 20121011

Available from: 2009-03-18 Created: 2009-03-11 Last updated: 2012-10-11Bibliographically approved

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Lindbergh, Göran

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