-
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Proceedings
EFCF 2019 Low-Temperature
Fuel Cells, Electrolysers & H2 Processing
Chapter 05 - Sessions B02, B11, B15
B02: PEFC Degradation & Testing
B11: Acidic Membrane Materials B15: Diffusive Media for FC &
Electrolysers
Edited by Prof. Hubert A. Gasteiger (Chair)
Prof. Aliaksandr Bandarenka (Chair)
Co-Edited by Olivier Bucheli Gabriela Geisser Fiona Moore Dr.
Michael Spirig
Copyright © European Fuel Cell Forum AG
These proceedings must not be made available for sharing through
any open electronic means.
ISBN 978-3-905592-24-5
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PEFC Degradation & Testing, Acidic Membrane Materials,
Chapter 05 - Sessions B02, B11, B15 - 2/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
Chapter 05 - Sessions B02, B11, B15 B02: PEFC Degradation &
Testing B11: Acidic Membrane Materials B15: Diffusive Media for FC
& Electrolysers
Content Page B02, B11, B15 - ..
B0201 (Invited Talk)
...........................................................................................................
6 Multi-step Kinetic Model for Pt Dissolution
Kunal Karan (1), Barath Jayasankar (1,2) (1) Department of
Chemical and Petroleum Engineering, University of Calgary 2500
University Dr NW, Calgary, Alberta, Canada (2) FCP Fuel cell
powertrain GMBH, Chemnitz, Germany HRB 31357
B0203 (Published in EFCF Special Issue Series, www.EFCF.com/LIB)
...................... 11 CFD Simulation of Industrial PEM Fuel
Cells with Local Degradation Effects
Clemens Fink (1), Sönke Gößling (2), Larisa Karpenko-Jereb (3)
(1) AVL List GmbH, Hans-List-Platz 1, 8020 Graz, Austria (2) ZBT,
Carl-Benz-Str 201, 47057 Duisburg, Germany (3) Graz University of
Technology, Inffeldgasse 10/II, 8010 Graz, Austria
B0204 (Published in EFCF Special Issue Series, www.EFCF.com/LIB)
...................... 12 Sub-zero Start-up of Fuel Cell:
Diagnostics, Modelling, and Strategies
Jianbo Zhang (1), Fusen Huang (1), Shangshang Wang (1), Lei Yao
(2), Junning Wen (5), Jie Peng (2), Muriel Siegwart (3,4), Magali
Cochet (3), Pierre Boillat (3,4), Zhili Chen (5), Takemi Chikahisa
(6)
(1) School of Vehicle and Mobility, State Key Laboratory of
Automotive Safety and Energy, Tsinghua University, Beijing 100084,
China (2) Department of Engineering Mechanics, Tsinghua University,
Beijing 100084, China (3) Electrochemistry Laboratory (LEC), Paul
Scherrer Institut, CH-5232 Villigen PSI, Switzerland (4) Laboratory
for Neutron Scattering and Imaging (LNS), Paul Scherrer Institut,
CH-5232 Villigen PSI, Switzerland (5) Department of Mechanical
Engineering and Aeronautics and Astronautics, School of Science and
Technology, Tokai University, Hiratsuka 2591292, Japan (6) Division
of Energy and Environmental Systems, Graduate School of
Engineering, Hokkaido University, Sapporo, Hokkaido 0608628,
Japan
B0205 (Published in EFCF Special Issue Series, www.EFCF.com/LIB)
...................... 13 Predictive model for performance and
platinum degradation simulation of high temperature PEM fuel cells
in transient operating conditions
Ambrož Kregar (1,2), Gregor Tavčar (1), Andraž Kravos (1), Tomaž
Katrašnik (1) (1) UL, Faculty of Mechanical Engineering, Aškerčeva
6, SI-1000 Ljubljana, Slovenia (2) TU Graz, IPTC, Stremayrgasse 9
A-8010 Graz, Austria
B0206 (Abstract only, published elsewhere)
.................................................................
14 Carbon corrosion in PEMFC: linking startup/shutdown and
accelerated stress tests
A. Bisello, E. Colombo, M. Coppola, A. Baricci, A. Casalegno
Politecnico di Milano — Department of Energy, via Lambruschini 40,
Milano 20156 Italy
B1101 (Published in EFCF Special Issue Series, www.EFCF.com/LIB)
...................... 15 PBI-type Polymers and Acidic Proton
Conducting Ionic Liquids – Conductivity and Molecular
Interactions
Jingjing Lin, Jürgen Giffin, Klaus Wippermann, Carsten Korte
Forschungszentrum Jülich, Institut für Energie- und Klimaforschung
(IEK-3)
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Chapter 05 - Sessions B02, B11, B15 - 3/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
B1102
................................................................................................................................
16 Heteropoly Acid Based Membranes for Excellent Durability and
High Performance in Fuel Cell Applications
Andrew M. Herring, Andrew R. Motz, Mei-Chen Kuo Department of
Chemical and Biological Engineering Colorado School of Mines,
Golden, CO 80401, USA
B1103 (Abstract only, published elsewhere)
.................................................................
24 Chemical Stability Enhancement of Sulfonated Poly(arylene ether
ketone) Fuel Cell Membrane by Fixation of Cerium Ion
Yongman Park, Dukjoon Kim School of chemical Engineering,
Sungkyunkwan University, Suwon, Gyeonggi, 16419, Republic of Korea
Tel.: +82-31-290-7250
B1104 (Abstract only, published elsewhere)
.................................................................
25 Atomistic MD study of Nafion in dispersions: Understanding the
role of solvent in the ionomer aggregate structure, sulfonic group
clustering and acid dissociation
Atefeh Tarokh, Kunal Karan, Sathish Ponnurangam Department of
Chemical and Petroleum Engineering, University of Calgary 2500
University Dr NW, Calgary, Alberta, Canada
B1105 (Abstract only, published elsewhere)
.................................................................
26 Protic Organic Ionic Plastic Crystals as Novel Proton
Conductors
Jiangshui Luo, Yingting Yi, Michael Wübbenhorst Department of
Physics and Astronomy, KU Leuven Celestijnenlaan 200d - box 2416,
3001 Leuven, Belgium
B1106
...............................................................................................................................
27 Anion Influence on the Properties of Acidic Protic Ionic
Liquids
Hui Hou, Jürgen Giffin, Carsten Korte Forschungszentrum Jülich
GmbH, IEK-3 Wilhelm-Johnen-Straße, 52428 Jülich, Germany
B1107
...............................................................................................................................
33 Diagnosis of MEA Degradation for health management of Polymer
Electrolyte Fuel Cells
Derek Low, Lisa Jackson, Sarah Dunnett Department of
Aeronautical and Automotive Engineering Loughborough University
Loughborough, United Kingdom
B1110 (Abstract only, published elsewhere)
.................................................................
44 Investigating Polymer Membrane Durability in Polymer Electrolyte
Fuel Cells Operating at Intermediate Temperatures
Ahmed Ibrahim*, Ahmad El-kharouf Centre for Fuel Cell and
Hydrogen Research, School of Chemical Engineering University of
Birmingham, B15 2TT, UK
B1111 (Abstract only)
......................................................................................................
45 In situ estimation of the effective membrane diffusion
coefficient in a PEMFC
Kush Chadha, S. Martemianov, A. Thomas Institut Pprimé CNRS –
Université de Poitiers – ISAE-ENSMA – UPR 3346 SP2MI – Téléport 2
11 Boulevard Marie Curie BP 30179 F86962 FUTUROSCOPE CHASSENEUIL
Cedex EFCF 2019
B1112(Abstract only, published elsewhere)
..................................................................
46 Experimental and theoretical studies of transport properties of
a protic ionic liquid
Jiangshui Luo, Yingting Yi, Michael Wübbenhorst Department of
Physics and Astronomy, KU Leuven Celestijnenlaan 200d - box 2416,
3001 Leuven, Belgium
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Chapter 05 - Sessions B02, B11, B15 - 4/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
B1113 (Abstract only, published elsewhere)
.................................................................
47 Multi-block copolymers with highly sulfonated poly(arylene
sulfone) block for Proton Exchange Membrane Fuel Cells
Sang-Woo Jo (1,2), Hee-Tak Kim (1), Young Taik Hong (2), Tae-Ho
Kim (2) (1) Department of Chemical and Biomolecular Engineering,
Korea Advanced Institute of Science and Technology (KAIST) 291
Daehak-ro, Yuseong-gu, 34141, Daejeon/Republic of Korea (2)
Membrane Research Center, Korea Research Institute of Chemical
Technology 141 Gajeong-ro, Yuseong-gu, 34114, Daejeon/Republic of
Korea
B1114
................................................................................................................................
48 High-Temperature Polymer Electrolyte Fuel Cells based on Protic
Ionic Liquid Electrolytes
Josef Sanarov, Jürgen Giffin, Carsten Korte Forschungszentrum
Jülich GmbH Wilhelm-Johnen-Straße, DE-52428 Jülich
B1116 (Abstract only, published elsewhere)
.................................................................
55 Activation energy landscape for Brønsted acid−base systems
Yingting Yi, Jiangshui Luo, Michael Wübbenhorst Department of
Physics and Astronomy, KU Leuven Celestijnenlaan 200d - box 2416,
3001 Leuven, Belgium
B1501 (Published in EFCF Special Issue Series, www.EFCF.com/LIB)
...................... 56 Investigating the Influence of Structural
Modification of MicroPorous Layer and Catalyst Layer on Performance
and Water Management of PEM Fuel Cells through Neutron
Tomography
A. Mohseninia(1), D. Kartouzian(1), P. Langner (1), M.Eppler(1),
H. Markötter (2), J. Scholta (1),I. Manke (2)
(1) Zentrum für Sonnenenergie- und Wasserstoff-Forschung
Baden-Württemberg (ZSW), Helmholtzstraße 8, 89081 Ulm, Germany (2)
Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin,
Germany
B1502
...............................................................................................................................
57 Advances in PEM Fuel Cell Liquid Water Management
Preston Stolberg, Alexander Coverdill, Mehdi Mortazavi, Vedang
Chauhan, Jingru Benner, Anthony D. Santamaria
Department of Mechanical Engineering Western New England
University 1215 Wilbraham Rd, Springfield, MA 01119
B1503 (Abstract only, published elsewhere)
.................................................................
62 Mass transport of Water Vapor in a Polymer Electrolyte Fuel Cell
with Evaporation Cooling
Magali Cochet (1), Victoria Manzi-Orezzoli (1), Dirk Scheuble
(1), Pierre Boillat (1,2) (1) Electrochemistry Laboratory (LEC) (2)
Laboratory for Neutron Scattering and Imaging (LNS) Paul Scherrer
Institut, 5232 Villigen, Switzerland
B1504 (Abstract only)
......................................................................................................
63 Next Generation Gas Diffusion Layers (GDLs) – A Design for
Manufacture and Assembly (DFMA) Analysis
Whitney G. Colella (1), Jason Morgan (2) (1) Gaia Energy
Research Institute LLC, Arlington, VA, 22203-1966, USA (2) AvCarb
Material Solutions 2 Industrial Avenue, Lowell, MA, 01851, USA
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Chapter 05 - Sessions B02, B11, B15 - 5/65 Diffusive Media for FC
& Electrolysers
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B1505 (Abstract only, published elsewhere)
.................................................................
64 Correlation of porous transport layers properties and polymer
electrolyte water electrolysis performance
Tobias Schuler (1), Thomas J. Schmidt (1,2), Felix N. Büchi (1)
(1) Electrochemistry Laboratory, Paul Scherrer Institut CH-5232
Villigen-PSI, Switzerland (2) Laboratory of Physical Chemistry, ETH
Zürich, CH-8093 Zürich, Switzerland
B1506 (Abstract only, published elsewhere)
.................................................................
65 Direct water pathways in PEFC GDLs for improved liquid water
management
Christoph Csoklich (1), Thomas J. Schmidt (1,2), Felix N. Büchi
(1) (1) Electrochemistry Laboratory, PSI, Forschungsstrasse 111,
5232 Villigen PSI, Switzerland (2) Laboratory of Physical
Chemistry, ETH Zürich, 8093 Zürich, Switzerland
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Chapter 05 - Sessions B02, B11, B15 - 6/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
B0201 (Invited Talk)
Multi-step Kinetic Model for Pt Dissolution
Kunal Karan (1), Barath Jayasankar (1,2) (1) Department of
Chemical and Petroleum Engineering, University of Calgary
2500 University Dr NW, Calgary, Alberta, Canada (2) FCP Fuel
cell powertrain GMBH, Chemnitz, Germany HRB 31357
[email protected]
Abstract
Platinum and Pt-alloys remain the electro-catalyst with highest
activity for oxygen reduction reaction in the cathodes of polymer
electrolyte fuel cells (PEFCs). However, Pt-catalysts in PEFCs
undergo a loss of electrochemically active surface (ECSA) as a
result of cell potential changes experienced during operation.
Performance degradation arising from Pt ECSA loss is a key limiting
factor for PEFC durability. Understanding the mechanism of Pt ECSA
loss could lead to better control/mitigation strategies that can
arrest or minimize the loss. Platinum dissolution is the primary
mechanism of ECSA loss during potential cycling between 0.6V and an
upper potential of 1 V or higher. The mechanism of Pt dissolution
occurring during these cycles has not been fully understood. The
2012 groundbreaking work of Karl Mayrhofer and colleagues using the
electrochemical scanning flow (SCF) system coupled to ICP-MS system
revealed many new information on Pt dissolution [1]. It showed that
dissolution occurs both during anodic and cathodic scan, cathodic
dissolution was greater than anodic dissolution, and cathodic
dissolution rate increased with upper potential limit but anodic
dissolution was minimally affected. In this work, we present an
extension of our recently published unified model for O2
electrochemistry (oxide intermediates) comprising multi-step
reaction scheme that captures cyclic voltammetry, logarithmic oxide
growth and oxygen reduction reaction [2] to include the Pt
dissolution reaction (see reaction scheme below). This model is
able to simulate all key features of the SCF experiments. The
validated model provides a deeper insight into the Pt dissolution
mechanism.
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Chapter 05 - Sessions B02, B11, B15 - 7/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
Introduction Despite enormous research on non-precious metal
group metal (non-PGM) catalysts, the electro-catalytic activity of
Pt and Pt-alloys remain far superior than any of its contender. As
a result, Pt and/or its alloys remain the only pragmatic catalyst
solution for a functional PEFC stack. On the other hand, Pt
catalysts in a polymer electrolyte fuel cells (PEFCs) undergo a
loss of electrochemically active surface (ECSA) as a result of
potential changes experienced during operation. Performance
degradation arising from Pt ECSA loss is a key limiting factor for
PEFC durability. Understanding the mechanism of Pt ECSA loss could
lead to better control/mitigation strategies that can arrest or
minimize the loss. Many different mechanisms for Pt surface area
loss during operation has been proposed including Pt dissolution,
Ostwald ripening, particle agglomeration, particle detachment from
carbon support and corrosion of carbon support itself [3-5].
Platinum dissolution has been considered to be the key cause of Pt
electrochemically active surface area (ECSA) loss. The mechanism of
Pt dissolution/loss has been debated and summarized in review
articles, most recently by Deborah Meyers and co-workers [6], which
contains key references and discussion on the debate that had
existed regarding Pt dissolution mechanism. Interesting
observations have been made regarding the Pt dissolution phenomena.
Under potentiostatic conditions, observable Pt dissolution is noted
above 0.8 V and increases with an increase in potential [6]. Pt
dissolution rates are accelerated upon potential cycling. The rate
of dissolution depends on the shape of the potential scans, i.e.
the scan rate, the potential range, and the dwell at the
upper/lower potential [7]. Recently, in a novel flow cell
experiment, Mayrhofer and co-workers demonstrated that Pt
dissolution occurs both during anodic and cathodic scans of the
potential cycle [1]. Interestingly, they observed the Pt
dissolution rate to be significantly higher in the cathodic scan
compared to that during the anodic scan. The models for Pt
dissolution [8-10] capture many features of the Pt dissolution
phenomena but none have discussed the transient behaviour of Pt
dissolution during the cathodic and anodic scans observed [1]. In
this work, we extended of our recently published unified model for
O2 electrochemistry on Pt (oxide intermediates) comprising
multi-step reaction scheme that captures cyclic voltammetry,
logarithmic growth of oxide at high potential and oxygen reduction
reaction [2] to include the Pt dissolution reaction. Our model
considers Pt dissolution to occur via chemical dissolution of
oxides species. With a single tuning parameter, the model was able
to simulate all key features of the SCF experiments.
Key Points The details of the multi-step O2 electrochemistry
model can be found in Ref [2]. The present work extends that model
by including Pt dissolution, which is modelled via chemical
dissolution of two oxide species, the place-exchange oxide (O-Pt)
and hydroxide on such a place-exchanged site (O-Pt-OH):
O-Pt + 2H+ Pt2+ + H2O (1)
O-Pt-OH + 3H+ Pt2+ + H2O (2)
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Fuel Cells, Electrolysers & H2 Processing EFCF 2019 2 - 5
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Chapter 05 - Sessions B02, B11, B15 - 8/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
The kinetics follow a simple first-order dependency on the
surface concentration of the two oxide species:
Rate of dissolution = kdiss O-Pt or kdiss O-Pt-OH (3) Here,
three key results showing a direct comparison of recent data by
Mayrhofer and colleagues (Topalov et al [1]) exemplifying of the
trends observed in their experiments are shown. (a)
Potential-dependent rate of platinum dissolution: Figure 1 below
shows a comparison of the rate of platinum dissolution as function
of upper potential. Each cycle comprised of a triangular wave from
0.1 V (vs RHE) to UPL. As can be noted fro the Figure 1, the model
predictions are remarkably close to the experimental data. It must
be noted that the rate constant for dissolution (kdiss) was tuned
so as to match with a potential. The closeness of the experimental
data and model prediction implies that the simple Pt dissolution
model is able to capture the dissolution rate at 8 different
potentials. This was a surprising result. However, our results
imply that sub-surface oxides, which were modeled via an earlier
kinetic model to simulate logarithmic sub-surface oxide growth on
Pt, are the critical component for Platinum dissolution.
Figure 1. Platinum dissolution per cycle as a function of upper
potential limit (UPL) during a triangular wave from 0.2 V to UPL at
a scan rate of 10 mV/s.
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Fuel Cells, Electrolysers & H2 Processing EFCF 2019 2 - 5
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Chapter 05 - Sessions B02, B11, B15 - 9/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
(b) Pt dissolution during anodic and cathodic scan: One of the
most interesting revelations of the SCF experiments of Mayrhofer
and colleagues was to settle the question on when does Pt
dissolution occur during potential cycling – anodic or cathodic
scan? They showed that above 1.1 V of upper potential limit, the
dissolution during cathodic scans far exceeds the dissolution
during anodic scan. They also observed that the dissolved Pt amount
during anodic scan was a weak function of upper potential limit but
that during cathodic scan increased steadily with increasing upper
potential. Again, our kinetic model captures these two trends
surprisingly well as shown in Figure 2 below. The inset is the data
from the experimental study of Topalov [1].
Figure 2. Platinum dissolution during a potential cycle. The
upper potential limit in each subsequent triangular wave is
increasing. The lower potential limit is 0.2 V and the scan rate is
10 mV/s. (c) Effect of scan rate on Pt dissolution: Another
interesting result of the SCF experiments was the decrease in Pt
dissolution per cycle upon increase in scan rate. However, when the
same information is plotted on a per second basis, the Pt
dissolution increases with increasing scan rate. Again, the
simulation results from our model is able to capture these trends
remarkably well as shown in Figure 3 below. The dissolution rate
per cycle drops by more than a factor of two as the scan rate is
increased from 10 mV/s to 50 mV/s.
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Fuel Cells, Electrolysers & H2 Processing EFCF 2019 2 - 5
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PEFC Degradation & Testing, Acidic Membrane Materials,
Chapter 05 - Sessions B02, B11, B15 - 10/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
Figure 3. Platinum dissolution per cycle as a function of upper
potential limit (UPL) during a triangular wave from 0.2 V to UPL at
a scan rate of 10 mV/s.
Summary - Conclusion A kinetic model for dissolution of Pt is
introduced. The results shows that our simple chemical dissolution
model can adequately describe several different experimental trends
remarkably well. This lends credence to the dominant mechanism for
Pt dissolution as: chemical dissolution coupled to sub-surface
oxide coverage/concentration.
References [1] Topalov et al Angewandte Chemie Int. Ed., 51,
12613, (2012) [2] B. Jayasankar and K. Karan Electrochimica Acta,
273, 367 (2018) [3] Y. Shao-Horn et al Topics in Catalysis, 46, 285
(2007) [4] S. Cherevko et al., Nano Energy 29,275–298 (2016). [5]
F. A. de Bruijn et al., Fuel Cells, 08, 1, 3–22 (2008). [6] D.
Meyers et al, J Electrochem Soc (JES), 165, F3178 (2018) [7] A.
Kneer et al JES 165, F805 (2018) [8] R. Darling and J. Myers, JES,
150, A1523 (2003) [9] S. Rinaldo et al, J Phys Chem C, 114,5773
(2010) [10] R. Ahluwalia et al JES 160, F447 (2013).
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Fuel Cells, Electrolysers & H2 Processing EFCF 2019 2 - 5
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PEFC Degradation & Testing, Acidic Membrane Materials,
Chapter 05 - Sessions B02, B11, B15 - 11/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
B0203 (Published in EFCF Special Issue Series,
www.EFCF.com/LIB)
CFD Simulation of Industrial PEM Fuel Cells with Local
Degradation Effects
Clemens Fink (1), Sönke Gößling (2), Larisa Karpenko-Jereb (3)
(1) AVL List GmbH, Hans-List-Platz 1, 8020 Graz, Austria
(2) ZBT, Carl-Benz-Str 201, 47057 Duisburg, Germany (3) Graz
University of Technology, Inffeldgasse 10/II, 8010 Graz,
Austria
Tel.: +43-316-787-4618 Fax: +43-316-787-777
[email protected]
Abstract
The PEM fuel cell model of a commercial software package is
presented in full detail. The basic model is extended by two
chemical degradation effects: ionomer degradation and carbon
corrosion with Pt oxidation. The ionomer degradation model
describes the ionomer mass loss due to hydrogen peroxide formation
and subsequent radical attack of the ionomer. The carbon corrosion
model calculates the carbon mass loss caused by carbon oxidation
and the active area reduction due to Pt oxidation. The degradation
models are coupled with the agglomerate model of the catalyst
layer. The model is validated against measurements on a 50 cm2 cell
from ZBT. For these measurements, the cell is equipped with a
segmented bipolar plate and a segmented measuring board which can
be used to measure the current density distribution as well as the
high frequency resistance of every segment. In order to test the
predictability of the model at different operating conditions,
measurements for stoichiometry and pressure variations are carried
out. For the validation of the degradation model, calculated and
measured current density distributions of the cell, aged by an
accelerated stress test, are compared. Moreover, 3D results of the
fresh and aged cell are analyzed in detail and the influence of
operating conditions on fuel cell aging is pointed out.
Remark: The full paper is published in EFCF Special Issue Series
(www.EFCF.com/LIB, SI EFCF 2019) in Journal "FUEL CELLS - From
Fundamentals to Systems".
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Fuel Cells, Electrolysers & H2 Processing EFCF 2019 2 - 5
July, Lucerne/Switzerland
PEFC Degradation & Testing, Acidic Membrane Materials,
Chapter 05 - Sessions B02, B11, B15 - 12/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
B0204 (Published in EFCF Special Issue Series,
www.EFCF.com/LIB)
Sub-zero Start-up of Fuel Cell: Diagnostics, Modelling, and
Strategies
Jianbo Zhang (1), Fusen Huang (1), Shangshang Wang (1), Lei Yao
(2), Junning Wen (5), Jie Peng (2), Muriel Siegwart (3,4), Magali
Cochet (3),
Pierre Boillat (3,4), Zhili Chen (5), Takemi Chikahisa (6) (1)
School of Vehicle and Mobility, State Key Laboratory of Automotive
Safety and Energy,
Tsinghua University, Beijing 100084, China (2) Department of
Engineering Mechanics, Tsinghua University, Beijing 100084,
China
(3) Electrochemistry Laboratory (LEC), Paul Scherrer Institut,
CH-5232 Villigen PSI, Switzerland
(4) Laboratory for Neutron Scattering and Imaging (LNS), Paul
Scherrer Institut, CH-5232 Villigen PSI, Switzerland
(5) Department of Mechanical Engineering and Aeronautics and
Astronautics, School of Science and Technology, Tokai University,
Hiratsuka 2591292, Japan
(6) Division of Energy and Environmental Systems, Graduate
School of Engineering, Hokkaido University, Sapporo, Hokkaido
0608628, Japan
[email protected]
Abstract Cold start capability is the key bottleneck restricting
large-scale commercialization of
fuel cell vehicles in cold regions. Fundamental understanding of
freezing mechanism and utilization of super-cooled water is
essential to further enhance the PEFCs sub-zero start-up
capability. For this aim, this talk introduces our recent study on
the sub-zero startup of PEFC, including the diagnostic and modeling
of super-cooled water and ice, and the new strategies to start up
the cell.
Advanced characterization tools, such as Cryo-SEM, neutron
radiography, and electrochemical characterization methods, such as
dynamic cyclic voltammetry (CV), dynamic electrochemical impedance
spectroscopy (EIS), were employed in sub-zero start-up experiments
to reveal the behavior of super-cooled water and the effects of ice
formation on the sub-zero startup performance of fuel cell. The
stability of super-cooled water and ice distribution are related to
the cell size, operation conditions, and component properties. The
ice does not cover the surface of the catalysts, but rather blocks
the pores of cathode catalyst layer, resulting in the suffocation
of oxygen supply to the reaction sites.
Based on these characterizations, a three-dimensional
mathematical model was developed to simulate the transient start-up
process. The stochastic freezing behavior of super-cooled water is
considered, which is described by introducing the freezing
probability function. Based on the model, two failure mechanisms,
including anode dehydration and cathode pore blockage are
systematically investigated with various initial membrane water
content and startup current densities.
A single cell setup with adiabatic thermal boundary condition
was proposed and tested to simulate the cell in the center of the
stack. MPL was improved and the current control was designed to
improve the cold start capability. Besides a novel technique using
hydrogen pump method to start the cell from sub-zero temperature is
proposed and verified. Remark: The full paper is published in EFCF
Special Issue Series (www.EFCF.com/LIB,
SI EFCF 2019) in Journal "FUEL CELLS - From Fundamentals to
Systems".
http://www.efcf.com/Libhttp://www.efcf.com/LIB
-
Fuel Cells, Electrolysers & H2 Processing EFCF 2019 2 - 5
July, Lucerne/Switzerland
PEFC Degradation & Testing, Acidic Membrane Materials,
Chapter 05 - Sessions B02, B11, B15 - 13/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
B0205 (Published in EFCF Special Issue Series,
www.EFCF.com/LIB)
Predictive model for performance and platinum degradation
simulation of high temperature PEM fuel
cells in transient operating conditions
Ambrož Kregar (1,2), Gregor Tavčar (1), Andraž Kravos (1), Tomaž
Katrašnik (1) (1) UL, Faculty of Mechanical Engineering, Aškerčeva
6, SI-1000 Ljubljana, Slovenia
(2) TU Graz, IPTC, Stremayrgasse 9 A-8010 Graz, Austria Tel.:
+386-1-4771-305 Fax: +386-1-2518-567
[email protected]
Abstract High temperature polymer electrolyte membrane fuel
cells (HT-PEMFCs) are a promising and emerging clean energy
conversion technology. Simultaneous reduction of production costs
and prolongation of the service life are considered as significant
challenges towards their wider market adoptions. To successfully
tackle these challenges predictive virtual tools are applied during
the development process of HT-PEMFC systems. In order to achieve
significant progress in the addressed area, this contribution
presents an innovative modelling framework based on: a) a
mechanistically based spatially and temporally resolved HT-PEMFC
performance model and b) a modular degradation modelling framework
based on interacting partial degradation mechanisms (Figure 1). The
core principle of the HT-PEMFC performance model is a
computationally efficient approach combining 1D numerical and 2D
analytic solution, denoted HAN. HAN modelling approach on one side
allows for achieving high level of predictiveness in FC performance
modelling, which is crucial for adequate virtual integration of FC
in the plant model, and on the other side provides spatially and
temporally resolved data of degradation stimuli. The later are
crucial input parameters for the degradation modelling framework
and are used by it as inputs to adequate causal chains of
interacting partial degradation mechanisms. Presented results
confirm credibility of the proposed modelling framework in
modelling FC performance and Pt degradation as well as related
carbon corrosion. Owing to its structured basis that covers the
entire causal chain from FC operation and control over prediction
of FC performance and degradation stimuli to prediction of
degradation rates over longer time scales, the proposed innovative
modelling framework enables more efficient exploration of the
design space and higher fidelity model supported design of FC
systems including their control functionalities.
Figure 1: A schematic diagram of the intertwined degradation
mechanisms.
Remark: The full paper is published in EFCF Special Issue Series
(www.EFCF.com/LIB,
SI EFCF 2019) in Journal "FUEL CELLS - From Fundamentals to
Systems".
http://www.efcf.com/Libmailto:[email protected]://www.efcf.com/LIB
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Fuel Cells, Electrolysers & H2 Processing EFCF 2019 2 - 5
July, Lucerne/Switzerland
PEFC Degradation & Testing, Acidic Membrane Materials,
Chapter 05 - Sessions B02, B11, B15 - 14/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
B0206 (Abstract only, published elsewhere)
Carbon corrosion in PEMFC: linking startup/shutdown and
accelerated stress tests
A. Bisello, E. Colombo, M. Coppola, A. Baricci, A. Casalegno
Politecnico di Milano — Department of Energy, via Lambruschini 40,
Milano 20156 Italy
Tel.: +39-02-2399-3840 [email protected]
Abstract
Fuel Cell (FC) technology is broadly accepted as a long-term
solution for the replacement of internal combustion engines,
however for automotive application many requirements must be
observed, including specific needs such as tolerance to numerous
start-up/shutdown (SUSD). Carbon corrosion in the electrodes of
MEAs (membrane-electrode assembly) is known as a major cause for
voltage degradation during SUSD cycles, when a slow H2/air front
flow in the anode opposite an air-filled cathode leads to
reverse-current mechanism which increases cathode potential as high
as 1.5 V. This work aims at increasing the understanding of
degradation process that occurs during SUSD. Firstly, aging tests
on single cell, active area 25 cm2, were conducted using custom
setup that combine a segmented cell and local reference electrodes,
to investigate the link between performance decay and local
operating conditions during SUSD (to taking into account different
user profiles). The results at different operating parameters,
showed the predominant effect of temperature on degradation rate,
exhibiting the same trend for kinetic and mass transport loss
between SUSD and AST at 80°C (Figure 1 left). Conversely, at 40°C
performance loss was mitigated but, on the other hand, the
measurements with RHE indicated an increase of maximum potential
(Figure 1 right). To elucidate the complex contributions of carbon
corrosion, double layer and platinum oxidation during SUSD, a
modelling activity were introduced. Finally, we showed that
transient physical model, which considers simultaneously faradaic
and capacitive currents, gives a consistent fit with experimental
data collected during SUSD at different operating conditions.
Remark: Only the abstract is available, because the authors
chose to publish elsewhere.
Please see Presentations on www.EFCF.com/LIB or contact the
authors directly.
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Fuel Cells, Electrolysers & H2 Processing EFCF 2019 2 - 5
July, Lucerne/Switzerland
PEFC Degradation & Testing, Acidic Membrane Materials,
Chapter 05 - Sessions B02, B11, B15 - 15/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
B1101 (Published in EFCF Special Issue Series,
www.EFCF.com/LIB)
PBI-type Polymers and Acidic Proton Conducting Ionic Liquids –
Conductivity and Molecular Interactions
Jingjing Lin, Jürgen Giffin, Klaus Wippermann, Carsten Korte
Forschungszentrum Jülich, Institut für Energie- und Klimaforschung
(IEK-3)
Wilhelm-Johnen-Straße, 52425 Jülich Tel.: +49 2461 61-9804 Fax:
+49 2461 61-6695
[email protected]
Abstract
The operation of low temperature polymer electrolyte fuel cells
(LT-PEFC) at elevated tem-peratures of above 100°C would allow a
much simpler system setup: i) no feed gas humidi-fication, ii) a
more efficient cooling system (easier water and heat management),
iii) the possibility of recovering high-grade waste heat, and iv) a
higher tolerance against feed gas impurities. Currently, (high
temperature) HT-PEFC, based on phosphoric acid doped
poly-benzimidazole (PBI) membranes, cannot compete with the
performance characteristics of NAFION-based LT-PEFCs. The presence
of H3PO4 causes a slow cathodic oxygen reduc-tion reaction kinetics
(ORR). Thus, there is a necessity for new non-aqueous proton
con-ducting electrolytes operational for the temperature range
between 100–120 °C.
Proton conducting ionic liquids (PIL) with acidic cations are
promising candidates for the use as non-aqueous electrolytes at
operation temperatures above 100 °C. In this contribution, an
experimental study on the interaction of PBI based proton exchange
membrane (PEM) with a betaine-type highly acidic PILs is presented.
2-Sulfoethylmethylammonum triflate exhibits a ~3 times higher ORR
current densities on Pt compared to H3PO4 [1]. There is a (slow)
uptake of the electrolyte by PBI due to a swelling process, up a
weight increase of 135%. The doping process was monitored by Raman
spectroscopy, proving the protonation of base imidazole groups on
PBI chains. TGA measurements show stable coulombic interaction
between triflate group and PBI, which is provided by
protonation.
NMR analysis has been applied to elucidate the molecular
interactions between PBI, PIL and residual water, which is present
during fuel cell operation. The total conductivity depends highly
on the H2O concentration. The acidic betaine-type PIL is able to
protonate H2O. Thus, proton conduction may take place by a vehicle
transport via PIL cations or H3O+ but also by cooperative mechanism
involving both species. Proton exchange, respectively an
interaction between the polar groups and water can be observed in
the spectra, indicating a network of H-bonds in doped PBI.
Compared to the neat PIL, the proton conduction in the doped PBI
membrane is restricted due to the constraining network of the
polymer chains. To optimise the conductivity but also the uptake of
the PIL into the polymer, the use of solution casting methods has
been studied for these materials.
Remark: The full paper is published in EFCF Special Issue Series
(www.EFCF.com/LIB, SI EFCF 2019) in Journal "FUEL CELLS - From
Fundamentals to Systems"..
http://www.efcf.com/Libhttp://www.efcf.com/LIB
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Fuel Cells, Electrolysers & H2 Processing EFCF 2019 2 - 5
July, Lucerne/Switzerland
PEFC Degradation & Testing, Acidic Membrane Materials,
Chapter 05 - Sessions B02, B11, B15 - 16/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
B1102
Heteropoly Acid Based Membranes for Excellent Durability and
High Performance in Fuel Cell
Applications
Andrew M. Herring, Andrew R. Motz, Mei-Chen Kuo Department of
Chemical and Biological Engineering Colorado School of Mines,
Golden, CO 80401, USA
Tel.: +1-303-273-3730 Fax: +1-303-384-2081
[email protected]
Abstract
Heteropoly acids (HPAs), a subclass of the polyoxometalates, are
a class of proton conducting radical activating or decomposing
molecules. Several types of HPAs have demonstrated the ability to
improve membrane chemical stability through polymer blends, but
they still suffer from migration and only result in marginal gains.
A method of covalent bonding HPAs to carbon in the catalyst layer
has also shown some improvements in chemical stability, but
chemical degradation mitigation within the membrane is needed. Our
group has developed two membrane platforms with HPAs covalently
attached and immobilized within a polymer membrane, serving as the
proton conducting acid. More recently, the outstanding chemical
stability of one of these platforms has been demonstrated, however,
the stability demonstrated in this study was criticized for using
rather thick, 80 µm membranes in sub-scale fuel cells. In a recent
study a 50 cm2 fuel cell was fabricated using a thin, 25 µm
membrane with covalently attached silicotungstic acid, which was
subjected to an accelerated stress test for chemical degradation
and displayed an OCV decay rate of 520 µV h-1. To the authors
knowledge, this is the first reported fuel cell of a larger
practical area containing a hybrid HPA film and represents a
significant step towards demonstrating this technology on a
commercially relevant scale. The resulting data was analyzed to
show the loss in OCV is mainly due to an electrical short and not
increased reactant gas crossover. This study further analyzes the
chemical stability observed in these membranes and proposes a
mechanism for radical decomposition. A reaction mechanism is
proposed utilizing reactions found in literature as well as density
functional theory (DFT) calculations. The main conclusion from this
work is that covalently attached HPAs could be more efficient
radical scavengers with less susceptibility to migration,
accumulation, and leaching when compared to the use of Ce(III)
cations. We have recently realized a method for cleaning these
membrane materials, removing many of the impurities formed during
synthesis and have also begun to cross-link these material to
eliminate swelling and achieve a dimensionally stable films. These
much-improved materials show even higher performance in fuel cells
and could potentially solve many of the issues associated with the
PFSA materials.
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Fuel Cells, Electrolysers & H2 Processing EFCF 2019 2 - 5
July, Lucerne/Switzerland
PEFC Degradation & Testing, Acidic Membrane Materials,
Chapter 05 - Sessions B02, B11, B15 - 17/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
Introduction Electrochemical energy conversion devices have
great potential to replace the internal combustion engine and
transform the electrical grid; this can be accomplished with
batteries, fuel cells, or flow batteries. One main advantage that
fuel cells have over batteries when it comes to the automotive
sector is the rapid rate of refueling hydrogen is similar to
petroleum refueling. While the field has greatly progressed in the
last decade, some room for improvement still exists. The DOE has
developed technical targets for membranes for transportation
applications. At the core of this is the development of a membrane
with an ASR of 0.02 Ωcm2 at 80 °C and at the maximum operating
temperature of the envisioned fuel cell stack at low partial
pressures of water (pH2O 25 kPa at 80°C, 40 kPa at 120°C). Cross
over of 2 mA cm-2 for hydrogen and oxygen and a minimum electrical
resistance of 1,000 Ω cm2 need to be achieved. In addition, the
film should survive 20,000 cycles of the DOE wet/dry mechanical
test and >500 hours of the chemical crossover OCV test.
1. Scientific Approach We have developed completely new ionomer
systems based on incorporation of inorganic super acids into
polymer systems [1, 2], which have high proton conductivity under
conditions of low humidity, higher temperature operation, high
oxidative stability, and little swelling when wet. The technical
concept is to use functionalized inorganic super acids that utilize
little water for high proton conductivity, as the protogenic group
covalently attached to a polymer backbone optimized for all other
functions of the membrane. Many composite inorganic/polymer films
have been fabricated, but unless the particles have dimensions on
the nano-scale there is no advantage as the improvement to film
properties occurs at the particle polymer interface. The limit of
this approach is to use molecules with high acidity as the highly
activating functionalities, but to do this we must immobilize them,
control the morphology of the proton conducting channel, and
fabricate an amorphous material. In previous work, we demonstrated
both composite membranes and true inorganic/polymer hybrid
materials with very high proton conductivity, but the inorganic
super acid in the membrane was not immobilized and the
inorganic/polymer hybrid material transformed into undesirable
crystalline phases at low RH. These materials are not yet fuel cell
ready. In this project, we will overcome all of these disadvantages
with an innovative approach to amorphous materials to produce high
proton conductivity and all other properties desired of a PEM. The
HPA silicotungstic acid (HSiW) is able to conduct at high
temperatures with minimal hydration, making it an ideal acidic
moiety. This study discusses the synthesis of a new material based
on HSiW moieties covalently attached to a functionalized
perfluorinated elastomer. The use of HSiW results in a film with a
low area specific resistance (ASR) at elevated temperatures and
superior performance to Nafion® under standard operating
conditions. The material easily passes the DOE mechanical test due
to the perfluorinated backbone and the chemical test due to the
ability of the HPA to destroy oxygenated radicals [3].
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Fuel Cells, Electrolysers & H2 Processing EFCF 2019 2 - 5
July, Lucerne/Switzerland
PEFC Degradation & Testing, Acidic Membrane Materials,
Chapter 05 - Sessions B02, B11, B15 - 18/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
2. Experiments/Calculations/Simulations Materials: Diethyl
(4-hydroxyphenyl)phosphonate (DHPP) was purchased from Synquest
(catalog number 6677-1-07) and a
polyvinylidene-co-hexafluoropropylene (PVDF-HFP) fluoroelastomer
(FC-2178) was supplied by 3M. Hydrochloric acid (HCl) (37%, ACS
reagent grade) was purchased from Pharmco-Aaper. Sodium hydride
(NaH) (60% dispersion in oil) and bromotrimethylsilane (TMSBr)
(97%) were purchased from Sigma-Aldrich. All other reagents were
purchased from Sigma-Aldrich with >99% purity and were used as
received. Preparation of PolyPPE: FC-2178 (31.78 g) was washed with
methanol, dried at 40°C under vacuum for two days, then dissolved
in 150 mL anhydrous dimethylformamide (DMF). In a separate flask,
20.0 g DHPP was added to 100 mL anhydrous DMF and allowed to
dissolve at room temperature, followed by cooling to 0°C. Once
cooled, NaH was added slowly to the DHPP solution, under a N2(g)
flow, producing H2(g) bubbles. After 2 h, bubble formation subsided
and the FC-2178 solution was slowly added over a period of 30
minutes. The combined solution was then heated to 50°C and allowed
to react for 24 h, darkening with time, before precipitation in 1M
HCl. The precipitate is then isolated, washed with water, and dried
under vacuum for 48 h, producing phenol phosphonic ester
functionalized FC-2178 (PolyPPE). Preparation of PolyPPA: The
PolyPPE was then dissolved in 450 mL acetonitrile overnight at room
temperature. The following day, 32 mL bromotrimethylsilane (TMSBr)
was added under a N2 environment. The reaction was heated to 45°C
and allowed to react overnight, producing a cloudy mixture. The
reaction solution was filtered and the filtrate was dissolved in
600 mL MeOH with 20 mL concentrated HCl, quenching the reaction.
The reaction solution was dried resulting in the phenol phosphonic
acid functionalized FC-2178 (PolyPPA). The PolyPPA was subsequently
washed with water, dried, and stored at room temperature, yield =
38.5g (77%). Preparation of PolyHPA: 4.50 g PolyPPA was added to
180 mL n,n- dimethylacetamide (DMAc) and allowed to dissolve
overnight at 80°C. Next, 10.50 g -K8SiW11O39•13(H2O) (HSiW),
synthesized according to the protocol previously reported,(4) was
slowly added. The mixture was cloudy, but rapid stirring with a
magnetic stir bar ensured no precipitate formed on the bottom.
Next, 12 M HCl (1.356 mL) was added dropwise, turning the solution
into a transparent amber. The reaction took place over 70 h at 80
°C, then the solution was filtered with a paper filter followed by
a filtration using a medium porosity glass frit Büchner Funnel to
remove potassium chloride crystals. The volume was then reduced to
ca. 60 mL using a rotary evaporator. This solution was then cast on
Kapton® using a doctor blade to control thickness and dried at room
temperature over night (16 h). When dried, the films ranged from
20-80 µm. Next, thermal annealing under pressure (5 min, 26.7 kN,
160°C) was used to finish the attachment reaction and make the film
more uniform. The resulting film was then soaked in 1 M H2SO4 to
ion-exchange (3x) followed by rinsing in DI water (3x). Each rinse
was more than 1 h. Potentiostatic Electrochemical Impedance
Spectroscopy (PEIS). PEIS experiments were performed in a
TestEquity environmental chamber to accurately control the
temperature and relative humidity. The membranes were placed across
four platinum electrodes in cells designed after Bekktek FC-BT-115
conductivity cells and the PEIS measurements were performed using a
BioLogic VMP3 potentiostat. Data were fit using a Randles circuit
and the results were used to calculate an in-plane conductivity.
Small Angle X-ray Scattering (SAXS). The SAXS data was collected on
beamline 12-ID-B at the Advanced Photon Source, Argonne National
Lab in a custom built environmental chamber, using 13.3 keV
radiation. The chamber, described in detail elsewhere [5], is able
to control temperature and humidity and the conditions are outlined
below. A Pilatus 3M detector was used.
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Fuel Cells, Electrolysers & H2 Processing EFCF 2019 2 - 5
July, Lucerne/Switzerland
PEFC Degradation & Testing, Acidic Membrane Materials,
Chapter 05 - Sessions B02, B11, B15 - 19/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
Fuel Cell Testing: The Nafion standard membrane electrode
assembly (MEA) was fabricated using a catalyst coated membrane
(CCM), N211, with catalyst supplied by Tanaka Holdings Co. Ltd. The
anode catalyst layer consisted of TEC10EA30E, 30% Pt/C, 0.055 mg
cm-2 and a cathode catalyst layer consisted of TEC10E50EHT, 50%
Pt/C, 0.35 mg cm-2 and had an active area of 2x5 cm2. The PolyHPA
MEAs were fabricated using commercial gas diffusion electrodes
(GDE)s for both the anode and cathode (((Johnson Matthey Pt/C
electrocatalyst, PFSA ionomer, 0.35 Pt mg cm-2). The PolyHPA-70 (70
wt% theoretical HSiW loading) MEA had an active area of 2x5 cm2 and
the PolyHPA-75 (75 wt% theoretical HSiW loading) MEA was 5 cm2. The
10 cm2 fuel cells were run using flow rates, 4 L min-1 at the anode
and 8 L min-1 at the cathode while the 5 cm2 fuel cell was run
using flow rates of 2 L min-1 at the anode and 4 L min-1 at the
cathode.
3. Results A four-step synthesis, reported elsewhere [6], was
used to covalently attach HSiW to FC-2178, where
hexafluoropropylene accounts for ca. 20 mol% of the polymer [7]. To
avoid the over dehydrofluorination, the reagent was changed to NaH,
as the hydride is a stronger base than K2CO3, but still a weak
nucleophile. This change allows for attachment of DHPP at much
lower temperatures, Scheme 1. The polymer was processed into films
at 160°C for 5 min to enhance crosslinking and avoid thermal
decomposition.
Scheme 1: Full synthetic reaction scheme for the synthesis of
PolyHPA (final product) from
FC-2178 and DHPP
Two peaks appear in the SAXS, one at 0.097 and the other at 0.6
Å-1 corresponding to d-spacing values of 6.5 and 1.0 nm (Figure 1).
The 1.0 nm feature is likely the spacing between two adjacent HSiW
molecules and the 6.5 nm feature is likely the spacing between HSiW
rich and deficient domains. Interestingly with this system of HSiW
and PolyPPA, this same SAXS pattern predominates whenever the
material is processed. This strongly implies that a thermodynamic
minimum is achieved with clusters of HSiW separated by a
characteristic length of ca. 6.5 nm. Examination of the high q peak
shows a shift to lower q, or larger d-spacing that is highly
dependent on RH. This is indicative of water moving towards the
surface of the HSiW moieties and pushing them further apart.
F2
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Step1
1)CH3CNTMSBr
2)MeOH
Step2
K8SiW11O39HCl,DMAc
Step3
FC-2178 PolyPPE
PolyPPA PolyHPA
+
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Fuel Cells, Electrolysers & H2 Processing EFCF 2019 2 - 5
July, Lucerne/Switzerland
PEFC Degradation & Testing, Acidic Membrane Materials,
Chapter 05 - Sessions B02, B11, B15 - 20/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
The proton conductivity, seen in Figure 2, is >0.1 S cm-1 at
all of the temperatures measured (50-90 °C and 95 %RH) and exhibits
two different regimes of transport that
intersect near 60 °C, the T of the hydrophilic sidechains. The
values at 80 °C and 95 %RH are remarkably high, 0.228 and 0.298 S
cm-1 for the PolyHPA-70 and PolyHPA-75, respectively. This high
conductivity is achieved due the super acidic, and thus highly
mobile, nature of the protons of silicotungstic acid.
Figure 1: SAXS at 80 °C in air at various humidities and in
liquid water
Figure 2: In-plane conductivity of PolyHPA-70 at 95 %RH and
various temperatures with
trend lines to guide the eye.
Fuel cells were fabricated using commercial GDEs, which resulted
in good performance, see below. Figure 3a shows the cross-over data
for a fuel cell in the DOE mechanical AST, and it can be clearly
seen that the material passes. While this is an achievement, films
with mechanical supported are often able to easily pass this AST
and this problem is considered solved by many in the community. The
challenge that motivated this research was making a film that was
highly chemically stable. To test the hypothetical chemical
stability of this material, a chemical AST was performed at 90 °C,
30 %RH, under an H2-O2 environment at OCV. Under these conditions,
standard polymer electrolyte membranes degrade rapidly, this is due
to radical generation and subsequent attack of the polymer film. It
has been previously demonstrated that the decay is much more rapid
under an O2 environment, as used here, as opposed to air, the
standard DOE protocol [8]. Under O2 during this test Pt has been
shown to dissolve and precipitate as a Pt band in the membrane,
this phenomenon
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Fuel Cells, Electrolysers & H2 Processing EFCF 2019 2 - 5
July, Lucerne/Switzerland
PEFC Degradation & Testing, Acidic Membrane Materials,
Chapter 05 - Sessions B02, B11, B15 - 21/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
is also seen in real fuel cells that are cycled through OCV. The
accelerated degradation, in the AST using O2, has been attributed
to decomposition of the PFSA polymer near the Pt band, which is
more prevalent in O2 environments [9]. Below in Figure 3 b is the
OCV vs. time for two different batches of PolyHPA-70 (80 µm) and a
Nafion® 211 control. This remarkably low OCV decay (100 µV hr-1),
without OCV recovery, and under very harsh conditions represents
the lowest rate reported to date in the literature [10].
Figure 3: (a) LSV for PolyHPA-70 (80 µm) after wet/dry cycling
and beginning of life and
end of life crossover targets (b) OCV hold test at 90 °C/ 30 %RH
under H2-O2 flow and no current. Two different batches of
PolyHPA-70 (80 µm) easily pass the test while N211 film for
comparison (bottom trace). The typical target is 500 h while
retaining a voltage above
0.8 V which is marked (x). The PolyHPA-70 fuel cell was
evaluated under low humidity operation at 80 °C, see Figure 4. A
drop in voltage and an increase in HFR is seen, as expected as the
RH is dropped. At low current densities the HFR starts out near
1000 mΩ cm2, but drops to 141 mΩ cm2 at 2 A cm-2. This HFR drop can
be attributed to increase in water generation from increasing
current densities. Looking at the HFR values at low current
density, an order of magnitude increase occurs when the humidity is
reduced from 100 to 50 %RH, indicative of poor transport under low
RH. Finally, a full scale 50 cm2 MEA using a 30 µm PolyHPA-70 film
was prepared and tested at NREL [11] . The goal of this test was to
ensure the chemical stability was sufficient even with thinner
films where H2 crossover is higher and chemical stability is
lowered. This was the first MEA of this size and the performance
was worse than the smaller fuel cells with films of similar
thickness and membrane composition. This is mainly attributed to a
high
interface resistance between the PolyHPA-70 membrane and the
Nafion GDEs. See the polarization data in Figure 5 compared to the
data in Figure 4. The HFR at 80 °C and saturated gasses (ca. 200 mΩ
cm2) is much higher than would be expected with a PolyHPA-70
membrane that is 30 µm thick. This is attributed to the need to
optimize the fuel cell design for this new material and should not
affect the chemical stability. After the preliminary data
collection in a H2-O2 environment, a standard OCV hold in H2-air at
90°C and 30 %RH was performed with hydrogen crossover measurements
at 20-72 h intervals. After 500 h, the OCV had dropped to 0.72
V.
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Fuel Cells, Electrolysers & H2 Processing EFCF 2019 2 - 5
July, Lucerne/Switzerland
PEFC Degradation & Testing, Acidic Membrane Materials,
Chapter 05 - Sessions B02, B11, B15 - 22/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
Figure 4: PolyHPA-75 voltage (a) and HFR (b) at different
humidities vs. current at 80°C.
Figure 5: I-V data for the 50 cm2 fuel cell fabricated using a
30 µm PolyHPA-70 film.
Figure 6: Crossover from LSV for different types of
crossover.
The slope used to calculate the electrical shortage was much
higher later in the test and resulted in negative values for the
artificial, H2 crossover only current. While the H2 crossover
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values are not reliable, what is clear is the electric short
current increases with OCV hold test time and can be attributed to
the drop in OCV, not an issue with H2 crossover, Figure 6. The
membranes are not mechanically supported and likely suffer from
thinning under high compression. Mechanical support must be
investigated in the future to stop membrane thinning and electrical
shorting.
References [1] J. L. Horan, A. Lingutla, H. Ren, M. C. Kuo, S.
Sachdeva, Y. Yang, S. Seifert, L. F.
Greenlee, M. A. Yandrasits, S. J. Hamrock, M. H. Frey and A. M.
Herring, Journal of Physical Chemistry C, 118, 135 (2014).
[2] A. M. Herring, Journal of Macromolecular Science, Part C:
Polymer Reviews, 46, 245 (2006).
[3] A. R. Motz, M.-C. Kuo, J. L. Horan, R. Yadav, S. Seifert, T.
P. Pandey, S. Galioto, Y. Yang, N. V. Dale, S. J. Hamrock and A. M.
Herring, Energy & Environmental Science, 11, 1499 (2018).
[4] D. C. Duncan, R. C. Chambers, E. Hecht and C. L. Hill,
Journal of the American Chemical Society, 117, 681 (1995).
[5] Y. Liu, J. L. Horan, G. J. Schlichting, B. R. Caire, M. W.
Liberatore, S. J. Hamrock, G. M. Haugen, M. A. Yandrasits, S. n.
Seifert and A. M. Herring, Macromolecules, 45, 7495 (2012).
[6] A. R. Motz, M.-C. Kuo and A. M. Herring, ECS Transactions,
80, 565 (2017). [7] A. Taguet, B. Ameduri and B. Boutevin, Fuel
Cells, 6, 331 (2006). [8] A. Ohma, S. Suga, S. Yamamoto and K.
Shinohara, Journal of The Electrochemical
Society, 154, B757 (2007). [9] A. Ohma, S. Yamamoto and K.
Shinohara, Journal of Power Sources, 182, 39 (2008). [10] R. Yadav,
G. DiLeo, N. Dale and K. Adjemian, ECS Transactions, 53, 187
(2013). [11] A. R. Motz, M.-C. Kuo, G. Bender, B. S. Pivovar and A.
M. Herring, Journal of The
Electrochemical Society, 165, F1264 (2018).
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B1103 (Abstract only, published elsewhere)
Chemical Stability Enhancement of Sulfonated Poly(arylene ether
ketone) Fuel Cell Membrane by
Fixation of Cerium Ion
Yongman Park, Dukjoon Kim School of chemical Engineering,
Sungkyunkwan University, Suwon,
Gyeonggi, 16419, Republic of Korea Tel.: +82-31-290-7250 Fax:
+82-31-290-7272
[email protected]
Abstract
OH radicals are the major cause for the degradation of polymer
electrolyte membrane in polymer electrolyte membrane fuel cell
(PEMFC) or direct methanol fuel cell (DMFC) operation. As cerium
ion (Ce3+) is well known as an effective OH radical quencher, it is
introduced into membrane to convert the OH radicals into water for
long term anti-oxidation stability of polymer electrolyte in this
study. Additionally, aminoethyl-15-crown-5 is grafted on the
sulfonated poly (arylene ether ketone) (SPAEK) to prevent the
migration of cerium ions from the membrane, as
aminoethyl-15-crown-5 possibly forms a coordination complex with
cerium ions. The chemical and physical structure of the
aminoethyl-15-crown-5 grafted SPAEK are examined using 1H NMR, EDX,
and SAXS. The physical properties such as proton conductivity,
water uptake, and mechanical strength of the aminoethyl-15-crown-5
grafted SPAEK membrane are investigated and compared with those of
the aminoethyl-15-crown-5 blended and cerium blended ones. While
the grafting of aminoethyl-15-crown-5 does not significantly affect
the thermal and mechanical and water uptake behaviors of membranes,
it results in a significant improvement of anti- degradation effect
compared with other blend systems via Fenton׳s test. The proton
conductivity decreases with addition of cerium but its effect is
lessened by introduction of aminoethyl-15-crown-5. Dual sulfonation
of PAEK at the pendant site leads to enhancement of proton
conductivity.
Remark: Only the abstract is available, because the authors
chose to publish elsewhere.
Please see Presentations on www.EFCF.com/LIB or contact the
authors directly.
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B1104 (Abstract only, published elsewhere)
Atomistic MD study of Nafion in dispersions: Understanding the
role of solvent in the ionomer
aggregate structure, sulfonic group clustering and acid
dissociation
Atefeh Tarokh, Kunal Karan, Sathish Ponnurangam Department of
Chemical and Petroleum Engineering, University of Calgary
2500 University Dr NW, Calgary, Alberta, Canada Tel.:
+1-403-220-5754, +1-403-210-7342
[email protected], [email protected]
Abstract
Nafion belongs to the perfluorinated sulfonic acid (PFSA) class
of ionomers and serves its primary functionality of proton
conduction in the membrane and the catalyst layers (CLs) of polymer
electrolyte fuel cells (PEFCs). Its solvent-dependent structural
characteristics in dispersions and thereby in the colloidal
catalyst ink (comprising Pt/C catalyst and ionomer in a
solvent/media) has been speculated to play an influential role in
the structure, property and performance of CLs made thereof
[1-5].
We use fully atomistic Molecular Dynamics (MD) simulations to
investigate the dispersion of the Nafion ionomer in
hydrogen-bonding solvents with varying polarity (water, ethanol,
IPA and glycerol). Two distinct aggregation behavior is observed.
In water, the sulfonic acid is dissociated and aggregation of
backbone attributed to hydrophobic effect. In organic solvents, the
sulfonic group and the counter ions are not dissociated and
ionomers aggregate via the clustering of the ion-pairs. Network of
clusters of sulfonic groups forming the so-called hydrophilic ionic
domains are crucial for long-range proton transport in membranes
and ionomer thin films. Observed differences in finer-scale
structure of Nafion (and other ionomers) in different solvents may
help us understand what factors affect the transport properties of
the ionomers in the PEFC CLs.
Pure water
Remark: Only the abstract is available, because the authors
chose to publish elsewhere.
Please see Presentations on www.EFCF.com/LIB or contact the
authors directly.
Non-polar
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B1105 (Abstract only, published elsewhere)
Protic Organic Ionic Plastic Crystals as Novel Proton
Conductors
Jiangshui Luo, Yingting Yi, Michael Wübbenhorst Department of
Physics and Astronomy, KU Leuven
Celestijnenlaan 200d - box 2416, 3001 Leuven, Belgium
[email protected]
Abstract
High temperature polymer electrolyte membrane fuel cells
(PEMFCs) operating between 100 °C and 200 °C are desirable because
they offer significant benefits, such as improved electrode
kinetics, simpler water and heat management, and better tolerance
to fuel impurities, leading to higher overall system efficiencies
[1]. However, state-of-the-art high temperature PEMFCs suffer from
leakage problems associated with liquid electrolytes, such as H3PO4
and protic ionic liquids. Recently, organic ionic plastic crystals
(OIPCs) [2−6], which are unique electrolyte materials due to their
superior properties such as intrinsic ionic conductivity,
non-flammability, negligible vapor pressure, plasticity (mechanical
flexibility), high thermal stability, and wide electrochemical
window, are promising ionic conductors for electrochemical devices.
While the OIPCs used as electrolytes for PEMFCs should be
proton-conducting, they are often doped plastic crystals, which
employ acids, protic ionic liquids or bases as the dopants for
doping the matrix of certain neat plastic crystals. In order to
obviate the use of dopants that may be incompatible with the host
matrix of plastic crystals, we have developed some highly
proton-conductive pure plastic crystals which are protic OIPCs
(abbreviated as “POIPCs”) [3−6] and in essence are solid protic
organic salts formed by proton transfer from a Brønsted acid to a
Brønsted base. In this talk, we will present our recent work on
some pure POIPCs with wide plastic crystalline phases as novel,
fast solid-state proton conductors for the realization of
all-solid-state high temperature PEMFCs [3−6]. The physicochemical
properties of POIPCs, including thermal, mechanical, structural,
morphological, thermodynamic, crystallographical, spectral and
ion-conducting properties, as well as proton conducting mechanisms,
isotope effects and fuel cell performances, are studied
comprehensively in both fundamental and device-oriented
aspects.
References [1] Q. Li, J. O. Jensen, R. F. Savinell, N. J.
Bjerrum, Prog. Polymer Sci., 34 (2009) 449-477. [2] D. R.
MacFarlane, M. Forsyth, Adv. Mater., 13 (2001) 957-966. [3] J. Luo,
Ph.D. Thesis, KU Leuven, 2012. [4] J. Luo, O. Conrad, I. F. J.
Vankelecom, J. Mater. Chem. A, 1 (2013) 2238-2247. [5] J. Luo, A.
H. Jensen, N. R. Brooks, et al., Energy. Environ. Sci., 8 (2015)
1276-1291. [6] X. Chen, H. Tang, T. Putzeys, J. Sniekers, M.
Wübbenhorst, K. Binnemans, J. Fransaer, D. E. De Vos, Q. Li, J.
Luo, J. Mater. Chem. A, 4 (2016) 12241-12252.
Remark: Only the abstract is available, because the authors
chose to publish elsewhere. Please see Presentations on
www.EFCF.com/LIB or contact the authors directly.
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B1106
Anion Influence on the Properties of Acidic Protic Ionic
Liquids
Hui Hou, Jürgen Giffin, Carsten Korte Forschungszentrum Jülich
GmbH, IEK-3
Wilhelm-Johnen-Straße, 52428 Jülich, Germany Tel.:
+49-2461-61-85360 Fax: +49-2461-61-6695
[email protected]
Abstract
To run polymer electrolyte fuel cells (PEFCs) at an operating
temperature above 100 °C, there is a growing need for new proton
conducting membrane electrolytes that can be used when water
activity is low. This would allow for a system setup without feed
gas humidification and a more efficient cooling system. Nafion®
membranes as used for low temperature PEFCs (LT-PEFCs) suffer from
drying effects which will result in very low proton conductivity.
H3PO4 doped PBI membrane, as used in high temperature PEFCs
(HT-PEFCs), will result in a low power density because of low O2
solubility, as well as a specific adsorption of H3PO4 species on
the platinum redox catalyst. Proton conducting ionic liquids (PILs)
based on sulfonic acid derivatives may be used as alternative
liquid electrolytes because they exhibit sufficient proton
conductivity, electrochemical and thermal stability over a wide
temperature range and specifically faster ORR kinetics compared to
H3PO4 [1]. It was shown in a previous work by Wippermann et al.
that the ORR limiting current density of the 2-sulfoethylammonium
triflate with a strong acidic cation is significantly higher
compared to H3PO4 in a high potential range [2]. However, the
conductivity is about one order of magnitude lower. In this study,
we investigate strong acidic PILs based on a
2-sulfoethylmethylammonium cation combined with various anions such
as HSO4-, mesylate, tosylate, benzenesulfonate and triflate.
Acidity influence of the anion on the ORR kinetics (oxygen
diffusion coefficient and oxygen solubility), thermal and
electrochemical stability as well as conductivity, was measured at
different temperatures for the neat PILs as well as for various
amounts of water. The measured values are compared to phosphoric
acid and correlated to the anion properties to find an optimum.
Literature: [1] Mitsushima, Shigenori, et al. Electrochimica Acta
55 (22), 6639-6644 (2010). [2] Wippermann, Klaus, et al. Journal of
The Electrochemical Society 163.2, F25-F37 (2016).
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Introduction State-of-the-art low temperature polymer membrane
fuel cells (PEFC) based on Nafion® membranes, are still facing with
drying problem when increasing the operation temperature beyond 80
°C. A complex feed gas humidification and a water recirculation
system are necessary. Thus, high temperature PEFCs (HT-PEFC) were
widely investigated. HT-PEFC based on phosphoric acid (H3PO4) doped
polybenzimidazole membranes (PBI), allow operation of up to 160 °C
– 180 °C. There are many advantages for the application of HT-PEFC:
(i) no water management system, (ii) tolerance against feed gas
impurities like CO, (iii) the high grade waste heat can be used in
the system[1]. However, H3PO4 species have a poisoning effect on
the Pt redox catalyst and a low solubility of O2 in H3PO4 result in
a sluggish ORR (oxygen reduction reaction) kinetics[2]. In this
experimental study the basic electrochemical properties of protic
conducting ionic liquids (PIL) are investigated, providing their
use as alternative electrolytes for fuel cell applications. The
requirements for a suitable PIL are as follows: (i) thermal
stability up to at least 120 °C, (ii) electrochemical stability,
(iii) sufficient conductivity (10-1 - 10-2 S/cm), (iv) fast ORR
kinetics, (v) possibility to upscale for production scale. A major
drawback of H3PO4 is the adsorption of phosphate species onto the
Pt surface[3]. While compared with H3PO4, sulfonic acid and
trifluoromethanesulfonic acid have less poisoning effect to a Pt
redox catalyst[4,5]. Thus, the anion of the PIL is varied from
HSO4-, mesylate, tosylate, benzenesulfonate to triflate and the
measured performances of the PILs are compared with H3PO4.
1. Scientific Approach The PILs are synthesized by a
neutralization reaction of a strong acid HA and an (organic) base
B. The reaction scheme is shown as follows:
HA + B ⇌ BH+ + A− [1]
In this study, N-methyltaurine is used as common base B. The
cation BH+ is referred as [2-Sema]. The acid HA is altered between
sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid,
benzenesulfonic acid and trifluoromethanesulfonic acid. The anions
A- are referred as [HSA]-, [MSA]-, [TSA]-, [BSA]- and [TfO]-,
respectively. The structure of the PIL [2-Sema][TfO], is shown as
follows:
Figure 1 Structure of the protic ionic liquid [2-Sema][TfO]
In the experiments section, the synthesis processes of PILs
([2-Sema][HSA], [2-Sema][MSA], [2-Sema][TSA], [2-Sema][BSA] and
[2-Sema][TfO]) are illustrated. The physical and electrochemical
properties of these PILs, such as the thermal stability, ionic
conductivity, oxygen reduction reaction kinetics, oxygen diffusion
coefficient and oxygen concentration (solubility), are
investigated.
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2. Experiments/Calculations/Simulations Synthesis of the PILs
[2-Sema][TfO]: N-methyltaurine (reagent, Biosynth) was dried at 120
°C overnight and cooled to room temperature under a nitrogen
atmosphere. Trifluoromethanesulfonic acid (reagent grade, 98 %,
Sigma Aldrich) was added to a stoichiometric (1:1) amount of
N-methyltaurine. The mixture was stirred at 90 °C for 1 hour.
Considering its strong hygroscopicity, [2-Sema][TfO] has to be
stored under nitrogen atmosphere. [2-Sema][HSA]: same procedure as
[2-Sema][TfO]. [2-Sema][MSA]: same procedure as [2-Sema][TfO].
[2-Sema][TSA]: Since p-toluenesulfonic acid is a solid at room
temperature, it was heated up to its melting point. The melted acid
was added to a stoichiometric (1:1) amount of N-methyltaurine. From
this point, the same synthesis procedure was adopted.
[2-Sema][BSA]: same procedure as [2-Sema][TSA]. Characterization of
water contents in PILs The water contents of neat PILs were
measured by using Karl Fischer titration (852 KF Titrando,
Metrohm). Since the PILs exhibit high viscosities, they were
diluted with water-free acetic acid. The mixtures were homogenized
for 30 min before starting the measurements. Thermal analysis
Thermal stabilities of PILs were examined with a Perkin Elmer STA
6000 device. All PILs samples were measured under nitrogen
atmosphere. ORR kinetics The ORR kinetics of the PILs were measured
in a three-electrode testing cell under ambient pressure in the
temperature range between 80 °C – 120 °C. The homemade Pt working
electrode with a diameter of 250 μm was used. The roughness factor
of the Pt surface was determined to 1.3. A palladium-hydrogen
electrode (Pd-H electrode) was used as a reference electrode. The
Pd-H reference electrode was prepared according to the
literature[6-8]. The testing cell with a volume of about 3 ml – 4
ml was in-house-designed. A schematic drawing of testing cell is
shown in Fig. 2. A Pt crucible (99.9 % purity, m&k GmbH) was
used both as the measurement vessel and as the counter electrode.
The measurement setup is described in detail by Wippermann et
al.[8].
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Figure 2 Schematic drawing of testing cell[8]
Before starting the electrochemical measurements, the PILs
samples were saturated with O2 for 2 h with a gas flow rate to 20
ml/min. The O2 flow rate was reduced to 10 ml/min during the
measurements to avoid disturbances. The temperature was monitored
in-situ by a thermocouple sensor. All electrochemical measurements
were performed by using the electrochemical workstation (Zahner
Elektrik GmbH). Conductivity measurements The total conductivities
of PILs were measured in the temperature range of 80 °C - 120 °C by
using the two-electrode testing cell as described above, see Fig.
2. The Pt electrode was used as working electrode and the Pt
crucible as counter electrode. The cell constant was determined
using 0.1 M KCl solution. The cell constant of 0.42 cm-1 was found
to be constant in the volume range between 3.7 ml and 5 ml.
3. Results ORR kinetics The ORR polarization curves in H3PO4,
[2-Sema][TfO], [2-Sema][HSA] and [2-Sema][BSA] with a water content
23 mol% at 100 °C are depicted in Fig. 3. In the potential range
between 0.8 V and 0.2 V, significantly different current densities
are observed and thus cell different performances can be measured.
At a cell potential of 0.7 V, the current density of [2-Sema][TfO]
is 5 times larger compared with H3PO4 and 26 times larger compared
with [2-Sema][BSA] as well as [2-Sema][HSA]. In the potential range
between 0.7 V and 0.9 V, which is relevant for fuel cell
application, [2-Sema][TfO] shows a better performance compared with
the other PILs and H3PO4. The comparison of the limiting current
densities is as follows:
jlim([2-Sema][TfO])/ jlim([2-Sema][BSA] ≈ 1.4,
jlim([2-Sema][TfO])/ jlim(H3PO4) ≈ 4,
jlim([2-Sema][TfO])/ jlim([2-Sema][HSA] ≈ 7.
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Figure 3 Polarization curves of ORR in PILs and H3PO4
Mass transport characteristics
The oxygen concentrations cO2s and the (Fick’s) oxygen diffusion
coefficients DO2s in the PILs chosen for investigation are
determined by chronoamperometry. Potential steps were applied to
the cell by switching from OCV to a potential in the region of the
limiting current and then back to OCV. The measured current as a
function of elapsed time was recorded. The dynamic I vs.t curves
were fitted with the Shoup-Szabo equation to determine the oxygen
diffusion coefficient and oxygen concentration[9] (Fig. 4). The
oxygen diffusion coefficients in the PILs are about 1 magnitude
smaller compared with H3PO4. However, the oxygen concentrations
(solubilities) in the PILs are 1 - 2 magnitude higher compared with
H3PO4. The highest solubilities in the measured temperature range
can be found in the case of [2-Sema][TfO].
Figure 4 Oxygen diffusion coefficients in H3PO4 and PILs (left),
oxygen concentrations in
H3PO4 and PILs (right), water contents in PILs and H3PO4: 23
mol%
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4. Conclusions The highest ORR limiting current at 100 °C can be
found for [2-Sema][TfO]. It outperforms H3PO4 by a factor of 5. The
ORR performance depends on the redox kinetics on the electrode
surface, which can be interfered by strong adsorption of anionic
species, but it also depends on the matter transport to the
electrode. [2-Sema][TfO] exhibits a worse oxygen diffusion
coefficient compared to phosphoric acid, but the oxygen solubility
seems to overcompensate this lack.
When comparing [2-Sema][TfO], [2-Sema][HSA] in respect to H3PO4,
the least influence on the ORR kinetics is found in the case of
[2-Sema][TfO] with the least nucleophilic anion (from the super
acid TfOH). Despite the fact that the oxygen diffusion coefficients
of both PILs are comparable and the oxygen solubility of
[2-Sema][HSA] is still higher compared with H3PO4, [2-Sema][HSA]
with a HSO4− anion performs worse compared with H3PO4.
References [1] Yasuda, Tomohiro, and Masayoshi Watanabe. MRS
bulletin 38.7 (2013): 560-566. [2] Hsueh, K‐L., et al. Journal of
the Electrochemical Society 131.4 (1984): 823-828. [3] Hsueh, K.
L., E. R. Gonzalez, and S. Srinivasan. Electrochimica Acta 28.5
(1983): 691
697. [4] Scharifker, Benjamin Ruben, Piotr Zelenay, and JO'M.
Bockris. Journal of the
Electrochemical Society 134.11 (1987): 2714-2725. [5] Zelenay,
P., et al. Journal of the Electrochemical Society 133.11 (1986):
2262-2267. [6] Fleischmann, M., and J. N. Hiddleston. Journal of
Physics E: Scientific Instruments 1.6
(1968): 667. [7] Vasile, M. J., and C. G. Enke. Journal of the
Electrochemical Society 112.8 (1965):
865-870. [8] K.Wippermann, J.Wackerl, W. Lehnert, B. Huber and
C. Korte, J. Electrochem. Soc.
163-2 (2016) F25-F37. [9] Shoup, David, and Attila Szabo.
Journal of Electroanalytical Chemistry and Interfacial
Electrochemistry 140.2 (1982): 237-245. [10] Hsueh, K. L., E. R.
Gonzalez, and S. Srinivasan. Electrochimica Acta 28.5 (1983):
691-
697.
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B1107
Diagnosis of MEA Degradation for health management of Polymer
Electrolyte Fuel Cells
Derek Low, Lisa Jackson, Sarah Dunnett Department of
Aeronautical and Automotive Engineering
Loughborough University Loughborough, United Kingdom
Tel.: +44 (0)1509 227309 [email protected]
Abstract
Diagnostics and health management are fundamental components in
a strategy to improve durability and lifetime of polymer
electrolyte fuel cells. Fuel cells require a range of operating
conditions to be well managed for achieving performance or
durability objectives. So far, water management issues and single
parameter diagnostics for individual degradation modes have been
the focus of research in the literature. However, there has been
minimal research on the application of fuzzy inference systems for
online, multiple parameter diagnosis of fuel cells. This research
presents an advanced fuzzy inference system for diagnostics and
health management of a membrane electrode assembly (MEA) for
polymer electrolyte fuel cells. The fuzzy inference system
facilitates simplified connections of the complex relationships
between numerous operating conditions and subsequent degradation
modes. The approach utilises the most important operating
parameters for diagnosis of high priority degradation modes using
multiple health sensors. The developed fuzzy inference system
classifies the fuel cell input data into simple linguistic
categories for example ‘cell voltage is very high’ or ‘stack
temperature is low’ through a fuzzification process. Based on a set
of antecedent-consequent (if-then) rules, an inference calculation
is performed without necessity for complex mathematical models.
This enables a fast diagnosis with fuel cell parameters classified
on a scale of inclusion to the linguistic categories. The
linguistic classification of a degradation mode is converted back
into a numerical value through a defuzzification process. The
output data can be used to inform the user on the fuel cell state
of health. The investigation has focused on the diagnosis of MEA
degradation as it has been identified as having critical impact on
fuel cell performance and lifetime. A single cell with a 25cm2
active area was used for testing under numerous moderate to extreme
operating conditions known to cause membrane and electro-catalyst
degradation. A database of if-then rules was initially developed
based on knowledge in the literature and refined with experimental
testing. Results so far have supported validation of the fuzzy
inference system membership functions and the rule base for
diagnosing the consequential degradation modes based on fuel cell
operating conditions. This diagnostic and health management
approach facilitates proactive decision making for mitigation
strategies to be employed according to performance or lifetime
targets and can increase fuel cell availability and lifetime
therefore improving the overall value of the system.
http://www.efcf.com/Libmailto:[email protected]
-
Fuel Cells, Electrolysers & H2 Processing EFCF 2019 2 - 5
July, Lucerne/Switzerland
PEFC Degradation & Testing, Acidic Membrane Materials,
Chapter 05 - Sessions B02, B11, B15 - 34/65 Diffusive Media for FC
& Electrolysers
www.EFCF.com/Lib ISBN 978-3-905592-24-5
Introduction Polymer electrolyte fuel cells (PEFC’s) are a
promising technology that can produce electricity efficiently with
zero carbon emissions. Therefore, the development of fuel cell
technology plays an important part in the decarbonisation of
industry and progression towards a low carbon sustainable society.
The reliability and durability of PEFC’s is still a remaining
technological challenge as industry lifetime targets for automotive
and stationary applications of 5,000hrs and 40,000hrs respectively
are yet to be achieved [1][2]. Achieving these targets are crucial
in order to compete with conventional technologie