LOLIPEM Long-life PEM-FCH &CHP systems at ... · Bogna GROCHOLA Cracow University of Technology,...

Project acronym: LOLIPEM website address: www.lolipem.eu

title: Long-life PEM-FCH &CHP systems at temperatures ≥100°C

Funding Scheme: Fuel Cells and Hydrogen Joint Undertaking (FCH JU)

Funding board: EC (FP7) and FCH JU

Starting date: January 1st, 2010

Duration: 36 months

Date of latest version of Annex I against which the assessment will be made: December 2009

Deliverable number: D 4.3 Deliverable: workshop on ”Membrane materials: preparation and characterization” Contractual deliver date: M6, July 2009 Responsible: Partner P2 “Università di Roma ”Tor Vergata” Tel: +39 06 72594385 Fax: +39 06 72594328 E-mail: [email protected] Authors: “Maria Luisa DI VONA”

Dissemination Level

PU Public X

PP Restricted to other project participants (including the Commission Services)

CO Confidential, only for members of the consortium (including the Commission Services)

GA N° 245339 Deliverable D4.3

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1st International Workshop on

Long life membranes based on PFSA & SAPs:

Preparation and Characterization

Contents

INTRODUCTION ............................................................................................................5

LIST OF THE PARTICIPANTS...........................................................................................7

SCIENTIFIC PROGRAM ..................................................................................................9

ABSTRACT OF THE PRESENTED CONTRIBUTIONS ...................................................... 11


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INTRODUCTION The 1st International Workshop on Long life membranes based on PFSA & SAPs: Preparation and

Characterization, was organized by URoma2, Professor Maria Luisa DI VONA, in the framework of

LLooLLiiPPEEMM ((LLoonngg--lliiffee PPEEMM--FFCCHH && CCHHPP ssyysstteemmss aatt tteemmppeerraattuurreess ≥≥ 110000 °°CC)) EEUU PPrroojjeecctt. The workshop

was held in Grottaferrata (Rome), at Hotel Villa Grazioli on March 17th-18th 2011.

This workshop aimed to bring together scientists and students interested in the study and

development of new Polymer Electrolyte Membrane Fuel Cells.

The workshop was attended by well-known scientists from 8 countries: Italy, Germany, France,

Switzerland, Spain, Poland, UK, USA.

44 participants were present, with 17 oral presentations and 2 invited lectures. 9 presentations

was held by member of the Lolipem consortium and 10 by external scientists.


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The workshop featured all aspects of synthesis and both structural and functional characterization

of membranes, mainly perfluorosulfonic acid (PFSA) and sulfonated aromatic polymers (SAPs), with

emphasis on their application in PEMFCs operating above 100 °C.

The level of participants and contributions was very high and intense scientific discussions were

stimulated throughout the workshop.

Consensual was the importance of long-time tests of membranes to assess the degradation

phenomena. Industry representatives insisted also on the cost criterion, which makes complicated

materials developments unsuitable for application. To this day, Nafion and sulfonated aromatic

polymers appear as the most suitable membranes for “intermediate temperature” PEMFC.

Two relaxed dinners complemented the program.


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LIST OF THE PARTICIPANTS Giulio ALBERTI University of Rome Tor Vergata, Italy

Alicia ARCE MATGAS, Barcelona, Spain

Francesco ARENA Saarland University, Germany

Salvatore Antonino ARICÒ CNR - ITAE Italy

Morin ARNAUD LCPEM, CEA Grenoble, France

Giuseppe BARBIERI CNR-ITM, Italy

Brian BENICEWICZ University of South Carolina, USA

Davide BERETTA EDISON, Italy

Adele BRUNETTI CNR-ITM, Italy

Mario CASCIOLA University of Perugia, Italy

Vito DI NOTO University of Padova, Italy

Maria Luisa DI VONA University of Rome Tor Vergata, Italy

Thierry DJENIZIAN University of Provence, France

Anna DONNADIO ITM-CNR, Italy

Barbara GALLENZI University of Rome Tor Vergata, Italy

Bogna GROCHOLA Cracow University of Technology, Poland

Mariska HATTEMBERGER University of Birmingham, UK

Rolf HEMPELMANN Saarland University, Germany

Hou HONGYING University of Provence, France

Deborah JONES AIME, University of Montpellier II, France

Mustapha KHADHRAOUI University of Provence, France

Philippe KNAUTH University of Provence, France

Chrystelle LEBOUIN University of Provence, France

Luciana LUCHETTI University of Foggia, Italy

Francesco LUFRANO CNR - ITAE INSTITUTE, Italy

Brunella MARRANESI University of Rome Tor Vergata, Italy

Piercarlo MUSTARELLI University of Pavia, Italy

Riccardo NARDUCCI University of Perugia, Italy

Oriol J. OSSÒ MATGAS, Barcelona, Spain

Luca PASQUINI University of Rome Tor Vergata, Italy

Riccardo POLINI University of Rome Tor Vergata, Italy

Joaquim SALLERAS MATGAS, Barcelona, Spain

Jean- Yves SANCHEZ LEPMI-CNRS, Grenoble, France


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Guenther SCHERER Paul Scherrer Institute, Switzerland

Mauricio SCHIEDA Centre for Materials and Coastal Research, Germany

Michael SCHUSTER Fumatech, Germany

Emanuela SGRECCIA University of Rome Tor Vergata, Italy

Anna STACHOWICZ Cracow University of Technology, Poland

Rafael SZAMOCKI Saarland University, Germany

Elena TOCCI CNR-ITM, Italy

Sebastiano TOSTO ENEA, Italy

Florence VACANDIO University of Provence, France

Lourdes F. VEGA MATGAS, Barcelona, Spain

Thomas ZAWODZINSKI University of Tennessee, USA


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SCIENTIFIC PROGRAM

First International LoLiPEM Workshop. Long life membranes based on PFSA & SAPs: Preparation and characterization

Scientific Agenda

Thursday March 17, 2011

10.00 – 10.10 M. Luisa DI VONA, Welcome and presentation of LoLiPEM EU project

Chair: M. Luisa DI VONA, University of Rome Tor Vergata, Italy

10.10 – 11.10 Invited Lecture: Deborah JONES, AIME, University of Montpellier II, France

Cross-linking and other approaches to the mechanical stabilisation of PFSA membranes

11.10 – 11.30 Coffee Break

Chair: Guenther SCHERER, Paul Scherrer Institute, Switzerland

11.30 – 12.30 Giulio ALBERTI, University of Perugia, Italy

Understanding proton conductor ionomers in the temperature range 20-140°C

12.30 – 13.00 Tom ZAWODZINSKI, University of Tennessee, USA

Studies of proton conduction in new materials

13.00 – 14.30 Lunch

Chair: Jean-Yves SANCHEZ, LEPMI-CNRS, Grenoble, France

14.30 – 15.00 Antonino ARICÒ, CNR-ITAE, Messina, Italy

High temperature operation of solid polymer electrolyte fuel cells based on a short side chain perfluorosulphonic membrane in combination with designed electrocatalysts

15.00 – 15.30 Mario CASCIOLA, University of Perugia, Italy

Gravimetric determination of the water uptake of ionomeric membranes as a function of temperature at controlled relative humidity

15.30 – 16.00 Arnaud MORIN, LCPEM, CEA Grenoble, France

Consideration of mechanical aspects on the degradation of PFSA membranes


Chair: Antonino ARICÒ, CNR-ITAE, Messina, Italy

16.20 – 16.50 Philippe KNAUTH, University of Provence, France

Ex-situ stability test of SAPs by thermogravimetric analysis

16.50 – 17.20 Brian BENICEWICZ, University of South Carolina, USA

Advances in PBI-PA membranes for high temperature PEM devices

17.20 – 17.50 Piercarlo MUSTARELLI, University of Pavia, Italy

New PBI-based membranes for HT-PEMFCs 19.30 Gala Social Dinner – Castel Gandolfo


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Friday March 18, 2011

Chair: Tom ZAWODZINSKI, University of Tennessee, USA

9.30 – 10.30 Invited Lecture: Guenther SCHERER, Paul Scherrer Institute, Switzerland

Degradation of solid polymer electrolytes in electrochemical cells. Some considerations

10.30 – 11.00 Francesco ARENA, Universität des Saarlandes, Germany Permeability measurements on polymer membranes for fuel cells


Chair: Giulio ALBERTI, University of Perugia, Italy

11.20 – 11.50 Vito DI NOTO, University of Padova, Italy

Effect of the anions on the properties of proton-conducting membranes based on neutralized Nafion 117, triethylammonium methanesulfonate and triethylammonium perfluorobutanesulfonate

11.50 – 12.20 Mustapha KHADHRAOUI, University of Provence, France

Mechanical analysis of polymers

12.20 – 14.00 Lunch

Chair: Deborah Jones, AIME, University of Montpellier II, France

14.00 – 14.30 Michael SCHUSTER, Fumatech, Germany

Membrane development for fuel cells at FuMA-Tech

14.30 – 15.00 Jean-Yves SANCHEZ, LEPMI-CNRS, Grenoble, France

Membranes based on macroporous high performance polymers filled by a CLIP for high temperature PEMFC membranes

15.00 – 15.30 Alicia ARCE, Matgas, Barcelona, Spain

Study and implementation of advanced control technologies to maximize PEM fuel cell durability


Chair: Philippe Knauth, University of Provence, France

15.50 – 16.20 Emanuela SGRECCIA, University of Rome Tor Vergata, Italy

Hybrid approach for improved SAP membranes

16.20 – 16.50 Francesco LUFRANO, CNR-ITAE, Messina, Italy

Development of Membranes Based on Sulfonated Polysulfone for Applications in Direct Methanol Fuel Cells

16.50 – 17.20 Giuseppe BARBIERI, ITM-CNR, Cosenza, Italy

Development of long life SAP membranes for PEMFCs based on SPEEK-WC

18.30 Medieval Night – Fumone


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ABSTRACT OF THE PRESENTED CONTRIBUTIONS


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Cross-linking and other approaches to the mechanical stabilisationof PFSA membranes

D. J. Jones and J. Rozière

ICGM-Aggregates, Interfaces and Energy Materials, University Montpellier 2

34095 Montpellier cedex 5, France

Properties of perfluorosulfonic acid (PFSA) membranes have been further improved in recent years following the better understanding of critical ageing processes. Despite these advances, the conductivity of PFSA at high temperature and low relative humidity is lower than that of the applications-driven target, and further improvement is still required. The limitation of the approach of increasing proton conductivity by lowering the polymer EW is that the polymer and membrane properties are also affected, with membranes showing increased water uptake and dimensional swelling. Cross-linking between polymer chains reduces swelling at high hydration levels, increases Tg, and improves membrane mechanical strength, and we have developed and screened a series of approaches for the covalent cross-linking of PFSAs in order to improve membrane mechanical properties and reduce membrane swelling in the presence of water.

On the one hand, novel side-chain component multifunctional monomers have been developed that are cross-linkable after membrane fabrication through the presence of reactive nitrile or bromide end groups. On the other, methodologies have been devised for cross-linking of low EW membranes in sulfonyl fluoride precursor form through reaction with a nitrogen-containing base to give sulfonamide end groups that are converted to sulfonimide cross-links on thermal curing. Here, the degree of cross-linking is regulated by the reaction conditions, and the probability of reaction is high. Further, there is no parasitic reaction as can occur in the case of residual –Br or –NC functions in unreacted side-chains. This presentation will describe the preparation and characterisation of a series of cross-linked PFSA membranes and will highlight the advantages and disadvantages of the various approaches.

[1] Y. M. Zhang, L. Li, J. K. Tang, B. Bauer, W. Zhang, H. R. Gao, M. Taillades-Jacquin, D. J. Jones, J. Rozière, N. Lebedeva and R. K. A. M. Mallant, Development of covalently cross-linked and

composite perfluorosulfonic acid membranes, ECS Trans., (2009) 25, 1469-147. Acknowledgements Funding through FP6 IPHE-GENIE and fruitful collaboration with Shanghai Jiao Tong University under contract 039016, are acknowledged with thanks.


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Studies of Proton Conduction in New Materials

Thomas A. Zawodzinski Jr.1,2*, Che-Nan Sun1,3, Manale Maalouf 1,3and Yujia Bai1

1) Department of Chemical and Biomolecular Engineering, University of Tennessee-Knoxville,

Knoxville, TN, USA 37996

2) Material Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA

3 ) Case Western Reserve University, Cleveland, OH USA 44120

Many studies of polymer electrolytes have been reported, including detailed studies of

conductivity and other transport properties as functions of water content. Nonetheless, several

gaps remain in our physical data for membranes, leading to issues related to interpretation. In this

presentation, we will discuss our recent efforts to improve our understanding. We will focus on

new PFSAs developed at 3M.

One seemingly prosaic property that is necessary for several purposes is density of the

membrane as a function of water content. These include analysis of conductivity, thermodynamic

analysis of molar volume of polymers and water in the membrane and validation of theory.

Density of PFSA and other membranes is surprisingly difficult to measure due to the mixed

hydrophilic and hydrophobic character and the non-uniformity of the thickness of most

membranes. The former makes standard ‘density balance’ measurements based on Archimedean

displacement of fluids difficult since the membrane imbibes most fluids. We are exploring air

pycnometry as a solution to this and will discuss results and prospects for this method. We will

also discuss the application of this information to the analysis of conductivity in new 3M PFSAs.

For low EW 3M materials, we find surprisingly high rates of water motion, correlated to

high conductivity, at low water contents. Determining the polymer/water system density enables

a precise calculation of proton mobility. Preliminary estimates suggest that proton mobility is

indeed enhanced, beyond expected effects of EW (i.e. charge carrier concentration) on

conductivity. Finally, recent results obtained with ‘extended side-chain’ materials will be

described.


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High Temperature Operation of Solid Polymer Electrolyte Fuel Cells Based on a Short Side Chain Perfluorosulphonic Membrane in combination with Designed

Electrocatalysts

A. S. Aricò*, A. Stassi, I. Gatto, G. Monforte, E. Passalacqua, V. Antonucci

CNR-ITAE, Via Salita S. Lucia sopra Contesse 5 – 98126 Messina, Italy

L. Merlo, C. Oldani, E. Pagano

Solvay Solexis, viale Lombardia, 20 20021 - Bollate (MI) Italy

* Corresponding author: Tel.:+ 39090624237. fax: +39090624247. E-mail address: [email protected] (A.S. Aricò).

A new Aquivion® E79-03S short-side chain perfluorosulfonic membrane with a thickness of 30

μm (dry form) and an equivalent weight (EW) of 790 g/equiv developed by Solvay-Solexis for high-

temperature operation was tested in a polymer electrolyte membrane (PEM) single cell up to a

temperature of 130 °C and at pressures up to 3 bar abs. For comparison, a standard Nafion®

membrane (EW 1100 g/equiv) of similar thickness (50 μm) was investigated under similar

operating conditions (pressurised cell).

The membranes were tested in conjunction with designed CNR-ITAE carbon supported Pt and

Pt-Co electrocatalysts. The electrochemical tests showed better performance for the Aquivion™

membrane as compared to Nafion® with promising properties for high temperature PEM fuel cell

applications.

Beside the higher open circuit voltage and lower ohmic constraints, a higher electrocatalytic

activity was observed at high temperature for the electrocatalyst-Aquivion® ionomer interface

indicating a better catalyst utilization. High temperature stack testing carried out at CNR-ITAE in

the framework of the FP6 Autobrane project with Solvicore and JMFC MEAs confirmed the good

perspectives of the Aquivion® membrane for PEMFCs.


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Gravimetric determination of the water uptake of ionomeric membranes as a function of temperature at controlled relative humidity

M. Casciola1, M. L. Di Vona2, A. Donnadio3

1 Dipartimento di Chimica, Università degli Studi di Perugia,

via Elce di Sotto 8, 06123, Perugia, Italy 2 Dipartimento di Scienze e Tecnologie Chimiche, Università degli Studi di Roma Tor

Vergata, Via della Ricerca Scientifica 1,00133 Rome, Italy 3 National Research Council, Institute for Membrane Technology (ITM–CNR), Via Pietro

BUCCI, Cubo 17C, 87030 Rende CS, Italy

The determination of the water content of ionomeric membranes is of fundamental

importance for understanding the dependence of ionic conductivity on temperature and relative humidity (RH), but it is rather problematic when the membranes are equilibrated at high temperature and RH values. To solve this problem we built up an apparatus allowing the gravimetric determination of water uptake at temperature up to 140°C and RH in the range 30-90%.

The apparatus consists of two intercommunicating compartments held at different temperatures. The cold compartment contains water, while the hot compartment houses a glass container with the membrane under test. Relative humidity (RH) in the hot compartment is calculated from the ratio between the pressures of saturated water vapour (p) at the temperatures of the cold (Tc) and hot (Th) compartment: RH = 100·p(Tc)/p(Th). The apparatus is equipped with a device which allows closing the membrane container with a teflon plug without opening the cell. After a suitable equilibration time (usually half a day), the sample container is closed, extracted from the cell and weighed. The water content is determined on the basis of the difference between the weight of the hydrated and anhydrous ionomer, taking into account the amount of water trapped in the glass container at the temperature and the RH of the experiment. In this connection, it was checked that the amount of water trapped in the empty container corresponds to that calculated for certain temperature and RH values.

This technique was used to determine the water uptake of a membrane of sulfonated polyethersulfone (SPES) with IEC=1.31 meq/g as a function of temperature (70 – 120°C) at RH=75% and as a function of RH (50-90%) at 100°C. It was found that the conductivity hysteresis observed upon thermal cycling between 70 and 120°C is associated with an hysteresis in the membrane

hydration which increases from λ=7.4 to λ=8.4 during the heating run and keeps nearly unaltered when the membrane is cooled to 70°C. At 100°C, an RH increase from 50 to 90% determines an

increase in hydration from λ=5.9 to λ=8.1 and in conductivity from 4·10-3 to 4·10-2 S cm-1. Similar experiments are in progress on Nafion 117 membranes and on sulfonated aromatic polymers. Acknowledgements The EU-FP7 (FCH-JU) project “LoLiPEM - Long-life PEM-FCH &CHP systems at temperatures higher than 100°C” (GA 245339) is gratefully acknowledged for co-funding this work.


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Consideration of mechanical aspects on the degradation of PFSA membranes

A. Morin1, S. Escribano1, N. Otmani1, G. Gebel2

1 CEA-Grenoble, DRT/Liten/DEHT/LCPEM, 17 rue des Martyrs Cedex 9 F-38054 Grenoble (France)

2 CEA-Grenoble, DSM/INAC, UMR SPrAM 5819, 17 rue des Martyrs F-38054 Grenoble, Cedex 9 (France)

The mechanical properties of recast and extruded Nafion® membranes (Young modulus, yield

strength…) have been characterized as a function of temperature and relative humidity, as well as

immersed in water. Recast membranes have a more “plastic” behaviour than extruded one. These

properties have been used as input data for a model of the mechanical behaviour of this

membrane. Then, the mechanical stresses and deformation of the Nafion® 112 in an operating

PEMFC under cycling operation has been simulated. The results show a residual stress and

deformation after cycling.

In parallel, we demonstrated that the membrane’s structure becomes anisotropic under

compressive stress higher than 5 MPa at 100%RH and ambient

temperature.

More over tensile stress performed on extruded and recast Nafion membranes after ageing

under cycling load show that their mechanical properties have been modified. The modifications

are more important near the gas inlets compared to the gas outlets and are different for the

recast membrane than for the extruded one. Especially, the elongation at break for the recast

membrane is strongly reduced near the gas inlet which is much less pronounced for the extruded

one.

All these results indicate that the mechanical stresses during PEMFC operation induce physical

modifications of the membrane. They could be a major cause of the membrane degradation.


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Ex-situ stability test of Sulfonated Aromatic Polymers

by Thermogravimetric Analysis

P. Knauth and H. Hou

University of Provence, Laboratoire Chimie Provence (UMR 6264

Centre St Jerome, 13397 Marseille, France

In this talk, we will discuss the use of high resolution Thermogravimetric Analysis (TGA) for the ex

situ study of the stability of Sulfonated Aromatic Polymers (SAP). After a short introduction on

some basics of TGA, we will present :

- Study of decomposition products by coupling TGA with on-line Mass Spectrometry

- Analysis of thermal stability of SAP membranes

- Determination of Degree of Sulfonation and Degree of Cross-linking of SAP membranes and

comparison with acid-base titration results

Acknowledgements

The EU-FP7 (FCH-JU) project “LoLiPEM - Long-life PEM-FCH &CHP systems at temperatures higher

than 100°C” (GA 245339) is gratefully acknowledged for co-funding this work.


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Advances in PBI-PA Membranes for High Temperature PEM Devices

Brian C. Benicewicz

Educational Foundation Distinguished Professor

Department of Chemistry and Biochemistry

USC NanoCenter

University of South Carolina

Columbia, SC 29208

Polybenzimidazole (PBI) polymers are excellent candidates for PEM fuel cell membranes

capable of operating at temperatures up to 200˚C. The ability to operate at high temperatures

may provide benefits such as faster electrode kinetics and greater tolerance to impurities in the

fuel stream. In addition, PBI membranes doped with phosphoric acid can operate efficiently

without the need for external humidification and the related engineering hardware to monitor

and control the hydration levels in the membrane. PBI membranes are currently being

investigated as candidates for portable, stationary, and transportation PEM fuel cell applications.

The development of the PBI membranes has also led to major advances in hydrogen

separation, purification, pumping, and compression technologies. The basic properties of these

membranes as high temperature (>100˚C) proton conductors, combined with the well-known

chemical stability, high tolerance to gas impurities, and potential for low cost, provide the

significant advancement in this enabling technology for hydrogen purification. In this

presentation, we will outline the development of the polymer membrane technology associated

with these devices and describe their applications in both the future hydrogen economy and

current industrial hydrogen gas user markets.


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New Pbi-Based Membranes For Ht-PEMFCs

P. Mustarelli

Dept. of Chemistry, University of Pavia, and INSTM, Via Taramelli 16, 27100 Pavia Italy

The current research on polymer electrolytes for fuel cells is focused on the optimization of

a membrane working at about 120°C and low humidity levels (<30%), which are the real operative

conditions in case of automotive applications (1). Among a wide variety of tested polymer

systems, PBI-based membranes, doped with phosphoric acid, are considered to be the best

alternative to Nafion, due to their high conductivity even with no or low humidification and other

promising electrochemical performances.

After a brief introduction on the problems of the membranes for HT-PEMFCs, I will report

on the experimental strategies followed in our laboratory in order to design better systems. First

of all new polymeric architectures, based on polybenzimidazole, have been synthesized with an

increased number of basic sites, differently interspaced along the polymer backbone.

Subsequently, composite membranes were prepared by dispersing in the previously prepared

matrices micro- and nanosized fillers, which differ for morphology, microstructure and chemical

nature. Finally, new monomers including oxygen and other chemical moieties have been

synthesized, and the consequent polymer have been prepared. Both in situ-electrochemical tests

and impedance spectroscopy were performed to evaluate the MEA performances.

1. P. Mustarelli, Fuel Cells, 10 (2010) 753.


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Degradation of Solid Polymer Electrolytes in Electrochemical Cells Some Considerations

Günther G. Scherer

Electrochemistry Laboratory

Paul Scherrer Institut 5232 Villigen Switzerland

[email protected]

A solid polymer electrolyte offers interesting features with respect to the engineering of the cell

design, however, also specific implications. This is particularly true for the concept realized in fuel

cell mode. The dual function of serving as electrolyte and gas separator asks for a multitude of

specific material properties, which have to be considered in the context of the duty cycle of the

total fuel cell system.

Next to performance and cost, longevity is an issue of paramount interest. Here again, the solid

polymer electrolyte, exposed to an extremely hash environment of simultaneously present H2, O2,

H2O, Pt-particles with nano dispersion, higher temperature and pressure, etc. is prone to be the

weak link of the whole component chain.

Next to integral degradation effects, specific local degradation of the polymer membrane show up

due to inhomogeneous reaction conditions, e.g., current density, temperature, gas concentration,

humidity, etc., within the electrochemical reactor fuel cell.

The presentation describes some of these specific local effects, points to advanced

characterization methods and gives an outlook on further challenges.


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Permeability and Diffusivity Measurements on Membranes for H2-PEMFC’s

Francesco Arena, Rafael Szamocki, Rolf Hempelmann

Physical Chemistry, Saarland University, 66123 Saarbrücken, Germany

After a brief review about the technique the results of hydrogen permeability and

diffusivity measurements, carried out with Nafion 117, 115 membranes, are presented. Up to now

all measurements were performed in a dry membrane state at different temperatures. A setup for

the future experimental determination of hydrogen- and oxygen permeability is presented

allowing measurements not only at different temperatures (from room temperature up to 120 °C),

but also at different relative humidities (0% up to 90%). This test bench includes a highly non-

corrosive measurement cell, as well a thermosetting unit, a gas humidifier, and a gas

chromatograph for quantitative gas analysis

.Acknowledgements




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Effect of the anions on the properties of proton-conducting membranes based on neutralized Nafion 117®, Triethylammonium methanesulfonate and

Triethylammonium perfluorobutanesulfonate

Vito Di Notoa,b, Matteo Pigaa, S. Lavinaa, G. Paceb, G. Giffina

aDipartimento di Scienze Chimiche, Università di Padova, Via Marzolo 1, I-35131 Padova (Pd),

Italy. bIstituto di Scienze e Tecnologie Molecolari del CNR (CNR-ISTM) c/o Dipartimento di Scienze

Chimiche, Via Marzolo 1, I-35131 Padova (Pd), Italy.

In order to obtain proton exchange membranes (PEMs) that can operate at temperatures greater

than 120°C and in anhydrous conditions, innovative materials based on polymeric membranes doped with proton-conducting ionic liquids (PCILs) have been recently developed1-3. In this report the effect of the proton-conducting ionic liquid (PCIL) anion structure on the properties of a Nafion 117® membrane neutralized with triethylammonium (TEA+) (nN117) and doped with PCILs is presented. This work describes the synthesis and properties of proton-conducting membranes obtained by the treatment of nN117 with one of the following ionic liquids: triethylammonium methanesulfonate (TMS) and triethylammonium perfluorobutanesulfonate (TPFBu). The resulting PCIL-doped membranes are labelled NTMS and NTPFBu, respectively. The thermal and mechanical properties of the membranes are investigated by TG, DSC and DMA analysis. Results indicate that: (a) the membranes are thermally stable up to 140°C; (b) the uptake of ionic liquid is ca. 25 and 40 wt% for NTMS and NTPFBu, respectively; and (c) the mechanical properties of the membranes collapse at T > 140°C. Information about the structure and the interactions between different components of the membranes is examined with FT-IR ATR spectroscopy. Broadband electric spectroscopy is used to investigate molecular relaxation and polarization phenomena. Results for the pure PCILs indicate that: (a) three interfacial polarizations associated with different mechanisms of proton transfer exist above the melting point; and (b) conductivities

of σTMS = 1.4·10-2S/cm and σTPFBu = 9·10-3S/cm at 130°C. Results for the doped membranes reveal: (a) the mechanism of long range charge transfer, which is mediated by the dynamics of the fluorocarbon polymeric matrix and of the ionic liquids; (b) three interfacial polarizations, which are dependent on the nanostructuring phenomena of the ionic liquid contained within the polar

domains of NTMS and NTPFBu; (c) two dielectric relaxations α and β, which are associated with the dipolar relaxations involving the ionic liquids and the nN117 matrix below the melting point of

the PCILs; and (d) conductivities of σNTMS = 6.1·10-3 S/cm and σNTPFBu = 1.8·10-3S/cm at 130°C. The results allow a mechanism of proton conduction to be proposed for both the pure ionic liquids and the doped membranes. (1) Lee, S. Y.; Ogawa, A.; Kanno, M.; Nakamoto, H.; Yasuda, T.; Watanabe, M. J. Am. Chem. Soc.

2010, 132, 9764. (2) Di Noto, V.; Negro, E.; Sanchez, J. Y.; Iojoiu, C. J. Am. Chem. Soc. 2010, 132, 2183. (3) Martinez, M.; Molmeret, Y.; Cointeaux, L.; Iojoiu, C.; Lepretre, J. C.; El Kissi, N.; Judeinstein,

P.; Sanchez, J. Y. J. Power Sources 2010, 195, 5829.


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Mechanical analysis of Polymers

M. Khadhraoui, H. Hou, and P. Knauth

University of Provence, Laboratoire Chimie Provence (UMR 6264)

Centre St Jerome, 13397 Marseille, France

The properties of solid polymeric materials depend strongly on the microscopic

arrangement of molecules and chains configuration. These properties depend also on the initial

chemical composition, the different compounds and the modifications introduced by grafting,

branching or cross-linking.

The tensile test is usually used to determinate the different mechanical characteristics of

membrane such as: Young’s Modulus (E) , Yield Stress (σy) tensile strength (σTS), elongation at

rupture (εr), ductility, brittle behaviours. These characteristics are linked to the microstructure and

the architecture or the configuration of chains in the three dimensions.

In this talk, we will present:

- The definitions of different mechanical characteristics obtained from Stress-Stain curves.

- The behaviour of membrane polymers under tensile tests

- The influence of the condition test and the effects of temperature (T) and Relative

humidity (RH) on mechanical properties.

- The Relaxation and the complex and varied experimental results

The selected illustrations, in this talk, concern the polymers materials sPEEK, PPSU, Nafion, and

some are issued from bibliography.

Acknowledgements




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Membranes based on macroporous High Performance Polymers filled by a

CLIP for High Temperature PEMFC membranes

D. Langevin1, Q.T. Nguyen1, S. Marais1, C. Chappey1, S. Karademir1, C. Iojoiu2, M. Martinez2, N. El Kissi3, R. Mercier4, J-Y.Sanchez2,*

* [email protected]

1. PBS – UMR CNRS 6270 & FR 3038. Université de Rouen, 76821 Mont-Saint-Aignan, France. 2. LEPMI – UMR 5279, CNRS, Grenoble INP, UdS, UJF, BP 75, 34402 Saint-Martin-d’Hères cedex,

France. 3. Laboratoire de Rhéologie, UMR 5520, BP 53, 38041 Grenoble cedex

4. LMOPS – UMR 5041, BP 24, 69390 Vernaison, France.

This contribution deals with new proton conducting membranes based on a macroporous

polymeric separator filled by a proton conducting ionic liquid, CLIP. The macroporous separator,

made from an amorphous High Performance polymer having a high Tg, was prepared by vapour

induced phase inversion (VIPS) in order to obtain highly interconnected porous films. The CLIP

tested is obtained by reacting a sulfonic acid with a tertiary amine and presents high enough

thermal stability to be used at elevated temperature. Membrane samples were prepared by

immersing macroporous films in the previous CLIP. The macroporous separator was characterized

by SEM, gas permeation and TGA tests. The conductivities and the mechanical performances of

the filled separators were investigated. The proton conductivity of the previous membrane was

only slightly decreased with regard to the pure ionic liquid (20 mS/cm as compared to 31 mS/cm at

130°C) and exhibited, up to at least 150°C, storage moduli exceeding 200 MPa. This combination

of high mechanical strength and low conductivity loss make these new membranes very attracting.


26

Study and implementation of advanced control technologies to maximize

PEM fuel cell durability

Alicia Arce, J. Oriol Ossó, Carlos Bordons and Lourdes F. Vega

MatGas

Campus de la Universitat Autònoma de Barcelona 08193 Barcelona - Spain

Polymer Electrolyte Membrane (PEM) fuel cells are considered good candidates for

replacing conventional power sources in stationary and automotive applications due to the fact

that they present good properties such as fast start-up, high power density and low operating

temperature (60-120oC). However, the relatively short life of these fuel cells is a significant

drawback to their commercialization. Therefore, an appropriate fuel cell operation is essential in

order to optimize global efficiency and reduce degradation effects on the membrane. In this work

we report on the study and implementation of advanced control technologies for the optimization

of PEM fuel cells operation. Model predictive control formulations are proposed to regulate PEM

fuel cell systems. In particular, air supply and temperature are herein studied because since these

variables are strongly related to degradation effects and global efficiency. Moreover, the feasibility

of real-time implementation of these controllers is demonstrated by experimental tests. These

advanced control strategies are implemented in the test-bench developed at Matgas under the

LoLiPEM project for long-term durability tests of high-temperature PEM fuel cells manufactured

with membranes developed by LoLiPEM partners.

Acknowledgements




27

Hybrid approach for improved SAP membranes

E. Sgreccia,1,2 P. Knauth,2 M. L. Di Vona1

1Dipartimento di Scienze e Tecnologie Chimiche, Università degli Studi di Roma Tor Vergata,

Via della Ricerca Scientifica 1,00133 Rome, Italy 2University of Provence, Laboratoire Chimie Provence (UMR 6264), Centre St Jerome, 13397

Marseille, France

In the quest for improved PEM fuel cell membranes, composite materials offer a

supplementary degree of freedom for conception. Mechanically reinforced composite SPEEK

membranes were prepared by addition of a silylated PPSU minority phase with phenyl-silanol

groups. The secondary phase maintains the mechanical stability of the membrane, whereas the

main component is responsible for proton conduction. Water uptake coefficients are spectacularly

lower than those of pure SPEEK. A clear correlation exists between the water uptake coefficient

and the elastic modulus of the membranes. At 100 C, proton conductivity decreases above 85% RH

for pure SPEEK, but continues to increase for the polymer blend. The membrane preparation must

be further simplified in order to be industrially applicable. A second strategy relies on the

simultaneous presence of the polymer matrix and inorganic, organically surface-modified titania

particles. In principle, this method allows modulating the desired properties by changing surface

functionalization and concentration of oxide particles with the goal of synergistic effects between

the two components. With hydrophilic titania, the proton conductivity is high, but the membranes

are inhomogeneous due to titania agglomeration. Membranes with hydrophobic titania are

instead very homogeneous, but lack high conductivity.


28

Development of Membranes Based on Sulfonated Polysulfone for Applications in Direct Methanol Fuel Cells

Francesco Lufrano*, Vincenzo Baglio, Orazio Di Blasi, Pietro Staiti,

Vincenzo Antonucci, Antonino S. Aricò

CNR – ITAE, Istituto di Tecnologie Avanzate per l’Energia “Nicola Giordano” Via Salita S. Lucia sopra Contesse n. 5 - 98126 S. Lucia - Messina, Italy

[email protected]

Nowadays, acidic polymer electrolytes based on perfluorosulfonic-acid membranes are widely used as electrolytes (e.g. Nafion-type membranes) in different applications, but high cost, low operating temperature, and high methanol crossover of Nafion membranes have limited their widespread commercial application1,2. These drawbacks have stimulated scientists worldwide to develop new materials as Polymer Electrolyte Membranes (PEMs) based on sulfonated aromatic polymers (SAPs) as an alternative to Nafion for application in DMFCs.

This paper reports on the research and development of PEMs based on composite membrane of sulfonated polysulfone and modified silica materials for application in a DMFC at different operating temperatures. The sulfonated polysulfone (SPSf) was synthesized using trimethyl silyl chlorosulfonate as the sulfonating agent in a homogeneous phase of chloroform3, whereas silica was modified by treatment with chlorosulfonic acid at room temperature4. The ion exchange capacities of sulfonated polymer were varied from 1.2 to 1.6 meq g-1 changing the mole ratio between the sulfonating agent and monomer unit of polymer. The composite membranes based on sulfonated polysulfone and modified silica were prepared by using a casting method from dimethyl acetamide solutions. Structural characterizations by scanning electron microscopy and infrared spectroscopy were carried out on the composite membranes. Moreover, they were characterized in terms of ion exchange capacity, methanol/water uptake, proton conductivity, thermal properties, and DMFC performance at various temperatures. The whole study involved (a) the choice of preparative conditions influencing the synthesis of sulfonated polysulfone, (b) the modification of silica and the optimization of silica content in the composite membrane, (c) the investigation of membranes as polymer electrolytes in DMFC single cell at different temperatures and d) life-time investigation.

The membrane of sulfonated polysulfone containing 10 wt.% of modified silica showed a promising performance in DMFC investigations at temperatures comprised between 30°C and 60°C. A maximum power density of 60 mW cm-2 was obtained at 60°C feeding 1M methanol solution at the anode and dry air at the cathode, both at atmospheric pressure. A preliminary short durability test for 100 h showed any performance decay during chrono-amperometry measurement (60 mA/cm2) at 30°C.

1. V. Neburchilov, J. Martin, H. Wang, J. Zhang, J. Power Sources, 169 (2007) 221-238. 2. M.A. Hickner, H. Ghassemi, Y.S. Kim, B.R. Einsla, J.E. McGrath, Chem. Rev. 104 (2004) 4587-

4612. 3. F. Lufrano, V. Baglio, P. Staiti, A. Stassi, A.S. Arico’, V. Antonucci, J. Power Sources 195 (2010)

7727–7733. 4. M.A. Zolfigol, Tetrahedron 57 (2001), 9509-9511.


29

Development of long life SAP membranes for PEMFCs based on SPEEK-WC

Enrica Fontananova1, Adele Brunetti1, Hongying Hou2, Philippe Knauth2, Francesco Trotta3, Enrico Drioli1, Giuseppe Barbieri1*

1The Institute on Membrane Technology (ITM-CNR), National Research Council, c/o The University of Calabria, Cubo 17C, Via Pietro Bucci, 87036 Rende CS, Italy;

2 Université de Provence-CNRS: Laboratoire Chimie Provence (UMR 6264), Centre St Jérôme, 13397 Marseille, France

3 Dep. of Chemistry, University of Torino, Via Pietro Giuria 7, 10125 Torino, Italy

Currently the most commonly used proton exchange membranes (PEMs) for fuel cell (FC) applications are based on perfluorosulfonic acid (PFSA) polymers, like Nafion. These PEMs have high proton conductivity and an excellent chemical stability. However, PFSA membranes have also high costs and an excessive permeability to the reagent species (H2 and O2 for H2-PEMFC; methanol and O2 for direct methanol -PEMFC) which limits not only the efficiency of the process, but also the Membrane Electrode Assembly (MEA) durability. A further disadvantage of the PFSA membranes is their relevant loss of conductivity if operated for a long period of time above 80 °C, because of dehumidification problems and irreversible anisotropic swelling [1]. As possible alternative to the expensive PFSA membranes, a huge number of non-fluorinated sulfonated aromatic polymer (SAP) membranes have been investigated [2]. In addition to their lower costs, another key aspect of SAP membranes is their usually lower gas and vapour permeability compared to PFSA membranes [3]. However non-fluorinated membranes are also generally characterized by a lower long-term stability in PEMFCs operative conditions. Consequently the development of PEMs able to conjugate low cost, high proton conductivity, good barrier properties and long-term stability is an important research area. In this work, ionomer membranes made of a sulfonated derivative of an amorphous polyetheretherketone, known as SPEEK-WC, have been prepared by solvent evaporation methods.

SPEEK-WC-based membranes are characterized by a lower methanol, H2 and O2 permeability with respect to Nafion 117. This difference is due to their lower diffusion coefficients, caused by the higher stiffness of the aromatic polymer chains of SPEEK-WC in comparison to the perfluorinated Nafion backbone [4].

In order to improve the durability of SPEEK-WC membranes three different strategies have been investigated: a) thermal annealing; b) blending with Nafion 1100 ionomer solutions c) chemical cross-linking with 1,5-diamino-2-methylpentane (DAMP). Ex-situ tests indicate that a particularly promising methodology for SPEEK-WC membranes is the third ones. In particular, TGA analyses indicate the formation of sulphonamide bonds in the membranes cross-linked with DAMP. These membranes showed increased hydrolytic and oxidative stability at high temperature (>100°C). However, a concomitant reduction in proton conductivity with respect to the un-treated samples was also observed. For these reasons, a systematic investigation of the cross-linking conditions has been carried out in order to optimize the membrane performance.

[1] G. Alberti , R. Narducci and M. Sganappa, J. Power Sources, 178 (2008) 575 [2] M. A. Hickner, H. Ghassemi, Y. S. Kim, B.R. Einsla, J.E. McGrath, Chem. Rev. 104 (2004) 4587 [3] K.D. Kreuer. J. Membrane Sci. 185 (2001) 29-39 [4] E. Fontananova, F. Trotta, J. C. Jansen, E. Drioli, J. Membr. Sci. 348 (2010) 326

Acknowledgements The EU-FP7 (FCH-JU) project “LoLiPEM - Long-life PEM-FCH &CHP systems at temperatures higher than 100°C” (GA 245339) is gratefully acknowledged for co-funding this work.

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