Workshop on Ion Exchange Membranes for Energy Applications –
27th – 29th June 2016 in Bad Zwischenahn (Germany)
In the last years, research on anion exchange membranes (AEM) and AEM based systems for energy applications increased dramatically. Therefore, the 2-day workshop “EMEA2016”, which is the 4th in this series, is dedicated to this topic. The event includes a panel discussion, oral and poster presentations and will start with a Get-together on Monday evening.
The main focus of the workshop will be on anion exchange membranes, their synthesis, characterisation, stability, and their performance in electrochemical applications. These can be fuel cells, electrolyzers, redox flow batteries, zinc-air batteries, reverse electrodialysis cells, and others. In addition, contributions in the field of catalysis for AEM based systems are welcome.
Monday June 27th
20:00 | Get-together
Tuesday June 28th
8:30 | Reception Desk Opens
9:00 | Welcome
9:15 | Session 1
Prof. Steven Holdcroft
Department of Chemistry, Simon Fraser University
8888 University Drive, Burnaby, Greater Vancouver, BC, V5A 1S6, Canada
A class of polymers that contains cationic moieties along the backbone, as opposed to the pendant groups, are the alkylated poly(benzimidazoles), wherein the integrity of the polymer backbone is directly related the stability of the benzimidazolium group. In this presentation, we report on the evolution of the synthesis of these polymers and expand it to phenylated poly(benzimidazoles), Selected properties will be discussed including utilization of these materials as both the membrane and ionomer in alkaline AEMFCs and water electrolyzers.
“Hydroxide-Stable Ionenes”, ACS Macro Letters, 3 (5) (2014) 444-447.
“The Control and Effect of Pore Size Distribution in AEMFC Catalyst Layers”, Electrochem. Soc, 163 (5) (2016) F1-F6.
“Poly(phenylene) and m-Terphenyl as Powerful Protecting Groups for the Preparation of Stable Organic Hydroxides”, Angewandte Chemie, 55 (2016), 4818-21.
“Hexamethyl-p-Terphenyl Poly(benzimidazolium): A Universal Hydroxide-Conducting Polymer for Energy Conversion Devices”, Energy & Environmental Science, accepted May 2016
Alkaline Exchange Membranes in Fuel Cells: From Single Cell to Stack System
Fuel cells based on anion exchange membranes (AEMs) are a potential route to alleviating fuel cell cost barriers that even today, in the age of production-scale fuel cell vehicles, hinders mass-market penetration of technology. This possible route arises primarily due to potential low-cost catalysts and cheaper, polyhydrocarbon-based membranes.
However, the path to commercialization of AEM fuel cells contains a number of technological barriers fundamental to the alkaline system, including slow kinetics of alkaline hydrogen oxidation, sensitivity of performance to CO2 and fuel cell water management; the latter being more challenging in alkaline environment due to high water production in the anode, and active water consumption as a reactant in the cathode. Additionally the AEM itself is a barrier due to lower conductivity and durability, high swelling, and high sensitivity to dry-out when compared with perfluorinated proton exchange membranes (PEM).
Looking briefly at the status of alkaline membrane fuel cell (AMFC) technology at Elbit, we see that these challenges can largely be met at stack- and system-level for a given MEA. However, it is becoming increasingly clear that the complexity, and therefore cost, of higher-level ‘fixes’ required at stack/system level can be greatly reduced with improved membrane performance.
Recent progress in AEM technology gives increasing weight to the possibility for AMFC systems to be truly competitive with PEM fuel cell technology. This talk will discuss the role of the AEM in addressing these fundamental AMFC drawbacks, with a view to quantifying advances that are still needed to fully close significant remaining performance-cost gaps.
10:15 | Poster Presentation and Coffee
10:45 | Session 2
Anion Exchange Membranes Containing Perfluoroalkyl Groups
Kenji Miyatake, Hideaki Ono, and Junpei Miyake
Clean Energy Research Center and Fuel Cell Nanomaterials Center
University of Yamanashi, 4 Takeda, Kofu, Yamanashi 4008510, Japan
Highly ion conductive and durable membranes are top issues for the practical applications of anion exchange membrane fuel cells (AEMFCs). In our previous study, we revealed that multiblock copolymer poly(arylene ether sulfone ketone)s exhibited high hydroxide ion conductivity due to well-developed phase-separation and high density of ammonium groups.1) However, the block copolymer membranes still experience chemical degradation at sulfone, ketone, and/or ether groups under the alkaline conditions.
Our idea for improving the stability of AEMs is to eliminate those heteratomo linkages from the polymer main chains.2) We report herein synthesis and characterization of novel anion exchange membranes composed of perfluoroalkyl chains and phenylene rings with ammonium groups (QPAFs).3) QPAFs were synthesized via monomer synthesis by Cu-catalyzed Ullmann coupling reaction, polymerization by Ni-catalyzed cross coupling reaction, Friedel-Crafts chloromethylation reaction, and quaternization reaction. QPAFs were soluble in polar organic solvents such as DMSO and methanol, and provided bendable and transparent membranes by solution casting. The QPAF membrane with optimized copolymer composition exhibited high hydroxide ion conductivity, excellent mechanical properties, and reasonable alkaline stability. Alkaline fuel cell using the QPAF used as the membrane and electrode binder achieved good performance.
1) M. Tanaka, K. Fukasawa, E. Nishino, S. Yamaguchi, K. Yamada, H. Tanaka, B. Bae, K. Miyatake, M. Watanabe, J. Am. Chem. Soc., 133, 10646-10654 (2011).
2) N. Yokota, M. Shimada, R. Akiyama, E. Nishino, K. Asazawa, J. Miyake, M. Watanabe, K. Miyatake, Macromolecules, 47, 8238-8246 (2014).
3) H. Ono, J. Miyake, S. Shimada, M. Uchida, K. Miyatake, J. Mater. Chem. A, 3, 21779-21788 (2015).
Robust Hydroxide Ion Conducting Aromatic Polymer Electrolyte Membranes
Department of Chemistry & Chemical Biology, Rensselaer Polytechnic Institute
110 8th Street, Troy, New York, USA
A variety of energy storage and conversion electrochemical devices, such as polymer electrolyte membrane fuel cells, redox flow batteries, and water electrolysis, rely on ion-conducting polymer electrolyte membranes to separate and transport ions between the anode and cathode.1-3 Among these membranes, anion exchange membranes (AEMs) continue to receive increased attention because of their advantages of fast liquid fuel oxidation reaction in alkaline media, efficient water management, and the ability to use non-precious metal electrocatalysts for oxygen reduction reaction.4-6 Additionally, AEM-based electrochemical devices (as opposed to the liquid alkaline system) prevent leakage of corrosive fuels and carbonate precipitation.5,7 However, the most significant challenges currently preventing the advancement of AEMs in clean energy conversion technology are their poor chemical and mechanical stabilities under strong alkaline environment and low anion conductivity. It is generally recognized that the stability of both polymer backbone and cation functional group play a crucial role in device durability.
In first part of the presentation, a chemically stable and elastomeric triblock copolymer, polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS), was functionalized with various benzyl- and alkyl-substituted quaternary ammonium (QA) groups for anion exchange membrane (AEM) fuel cell applications. Synthetic methods involving transition metal-catalyzed C–H borylation and Suzuki coupling were utilized to incorporate six different QA structures to the polystyrene units of SEBS. Changes in AEM properties as a result of different QA moieties and chemical stability under alkaline conditions were investigated. Anion exchange polymers bearing the trimethyl ammonium pendants, the smallest QA cation moiety, exhibited the most significant changes in water uptake and block copolymer domain spacing to offer best ion transport properties. It was demonstrated that incorporating stable cation structures to a polymer backbone comprising solely of C–H and C–C bonds resulted in AEM materials with improved long-term alkaline stability. After 4 weeks in 1M NaOH at 60 °C and 80 °C, all six SEBS-QA AEMs remained chemically stable. Fuel cell tests using benzyltrimethylammonium-containing SEBS (SEBS-TMA) as an AEM demonstrated excellent performance, generating one of the best maximum power density and lowest ohmic resistance with low Pt catalyst loaded electrode reported thus far. Both polymer backbone and cation functional group remained stable after 110 h lifetime test at 60 °C.
In second part of the presentation, high molecular weight, quaternary ammonium-tethered poly(biphenyl alkylene)s without alkaline labile C–O bonds were synthesized via acid-catalyzed polycondensation reactions for the first time. Ion-exchange capacity was conveniently controlled by adjusting the feed ratio of two ketone monomers in the polymerization. The resultant anion exchange membranes showed high hydroxide ion conductivity up to 120 mS/cm and excellent alkaline stability at 80 °C. This study provides a new synthetic strategy for the preparation of anion exchange membranes with robust fuel cell performance and excellent stability.
(1) Li, N.; Guiver, M. D. Macromolecules 2014, 47, 2175.
(2) Hickner, M. A.; Herring, A. M.; Coughlin, E. B. J. Polym. Sci. Pol. Phys. 2013, 51, 1727.
(3) Varcoe, J. R.; Atanassov, P.; Dekel, D. R.; Herring, A. M.; Hickner, M. A.; Kohl, P. A.; Kucernak, A. R.; Mustain, W. E.; Nijmeijer, K.; Scott, K.; Xu, T. W.; Zhuang, L. Energ. Environ. Sci. 2014, 7, 3135.
(4) Couture, G.; Alaaeddine, A.; Boschet, F.; Ameduri, B. Prog. Polym. Sci. 2011, 36, 1521.
(5) Merle, G.; Wessling, M.; Nijmeijer, K. J. Membr. Sci. 2011, 377, 1.
(6) Varcoe, J. R.; Slade, R. C. T. Fuel Cells 2005, 5, 187.
(7) John, J.; Hugar, K. M.; Rivera-Meléndez, J.; Kostalik, H. A.; Rus, E. D.; Wang, H.; Coates, G. W.; Abruña, H. D. J. Am. Chem. Soc. 2014, 136, 5309.
Reduced graphene oxide modified nickel as an efficient hydrogen evolution catalyst in alkaline water electrolysis
Debabrata Chanda1, Jaromír Hnát1, Igor A. Pašti2, Karel Bouzek1
University of Chemistry and Technology Prague, Technická 5, 166 28 Prague, CZ
University of Belgrade, Faculty of Physical Chemistry, Studentskitrg 12-16, 11158 Belgrade, Serbia
To find cheap, efficient and durable hydrogen evolution reaction (HER) catalysts is one of the major challenges when developing an alkaline water electrolysis system. Traditionally platinum group metals show excellent properties. They are, however, inacceptable due to the economic reasons. Platinum metals are followed by other transition metals, like Ni, Co, Fe and Cu. It is because their d‑orbitals valence electron configuration. For the alkaline water electrolysis process Ni is particularly interesting option because of its excellent corrosion stability in an alkaline environment. Main issue represents the fact that electrocatalytic activity of this metal towards HER deteriorates rapidly during operation due to the surface Ni‑hydride layer formation. Preventing formation of this layer thus represents an interesting challenge opening potentially new way to an efficient and cheap HER catalyst.
This contribution focuses on an electrochemically reduced graphene oxide (RGO)-modified Ni electrode,1 which has been found to show very promising properties. The experimentally determined characteristics of this electrode indicate superior electrocatalytic activity towards HER exceeding even Pt nanoparticles. The experimental data were successfully complemented by density functional theory calculations. Thermodynamic considerations led to the conclusion that H atoms, formed upon H2O discharge on the Ni cathode surface, spill onto the RGO, which serves as an H ad‑atom acceptor, enabling continuous cleaning of Ni-active sites and an alternative pathway for H2 production. This mode of action is rendered by the unique reactivity of RGO. Its origin consists in the presence of O surface groups within the graphene structure. The significant electrocatalytic activity and life time (˃35 days) of the RGO towards the HER under conditions of alkaline water electrolysis was demonstrated using rotating disk and single alkaline water electrolysis cell employing alkaline polymer electrolyte.
We acknowledge the financial support of this research received from the Grant Agency of the Czech Republic under project No. 16-20728S.
D. Chanda, J. Hnát, A. S. Dobrota, I. A. Pašti, M. Paidar, K. Bouzek: The Effect of Surface Modification by Reduced Graphene Oxide on the Electrocatalytic Activity of Nickel towards the Hydrogen Evolution Reaction, Phys.Chem.Chem.Phys., 17, 2015, 26864.
12:15 | Lunch
13:45 | Guided Tour through the NEXT ENERGY Laboratories
16:00 | Session 3
Performance Evaluation of Vanadium Redox Flow Battery using Sulfonated Ketone Based Polyer Membranes
Yongchai Kwona, Ho-Young Jeongb and Chanho Noha
aGraduate school of Energy and Environment, Seoul National University of Science and Technology, 232 Gongneung-ro, Nowon-gu, Seoul, 139-743, Republic of Korea.
aDepartment of Environment & Energy Engineering, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju, 500-757, Republic of Korea.
In order to improve electrical performances of vanadium redox flow battery (VRFB) such as energy efficiency, determining proper polymer electrolyte membrane (PEM) is critical. For doing that, in this research, sulfonated poly (ether ether ketone) (sPEEK) membranes are adopted and investigated. As already reported in ref , effect of the sPEEK membrane on VRFB performance is elucidated in terms of membrane thickness and their peformance results are compared with those of commertially made Nafion membrane, while chemical and structural attributes of sPEEK membrane are estimated in seveal prospects. First, in terms of chemical strcuture of the membrane, FT-IR and TGA are used. Second, optical inspection of the membeanes is also impemented by using SEM and AFM measurements. Third, vanadium permeability of the membranes is measured by UV-vis spectrophotometer and forth, membrane resistance is measured by electrochemical impedance spectroscopy. To do VRFB performance tests, different thick sPEEKs and Nafion 212 memebranes are used. As a result of that, 50 μm thick sPEEK (sPEEK-50) indicates low overpotential, high energy efficiency, high maximum power density. Superiority in performance of VRFB using sPEEK-50 is due to improvements in power efficiency .
From Fundamental Studies to Practical Materials for AEM Fuel Cells
Andrew M. Herring, Himanshu N. Sarode, Tara P. Pandey, Ye Liu, and Mei-Chen Kuo
Department of Chemical and Biological Engineering, Colorado School of Mines
Golden, CO 80401, USA
The potential of anion exchange membrane (AEM) fuel cells to provide inexpensive compact power from a wider variety of fuels than is possible with a proton exchange membrane (PEM) fuel cell, has continued to drive the research interest in this area. Alkaline catalysis in fuel cells has been demonstrated with non-precious metal catalysts, and with a variety of fuels beyond H2 and methanol. Alkaline fuel cells (AFCs), based on aqueous solutions of KOH, have serious drawbacks associated with system complexity and carbonate formation. Anion exchange membrane (AEMs) fuel cells have a number of advantages over both PEM fuel cells and traditional AFCs; however, although anionic conductivity in AEMs can be comparable to PEMs the chemical stability of membrane attached cations in hydroxide is still not always sufficient for practical applications. Recently, it has been recognized that a number of advanced cations, may give AEMs the needed chemical stability. In some circumstances simple trimethyl benzyl ammonium cations are stable up to 60°C allowing us to begin to study hydroxide and water transport in these systems from a fundamental standpoint. We use in-plane conductivity and multi-nuclear PFGSE to measure self-diffusion coefficients of the water and where possible, the ion, i.e. F–, carbonate and bicarbonate. Together with temperature and RH dependent SAXS we couple this information with the morphological changes in the materials.
These fundamental studies have led us more recently to begin to design AEMs that are amenable to scale up. For this we are fabricating membranes from random co-polymers of a cation functionalized monomer and a non-polar monomer for mechanical strength. These systems are also easily cross-linked, to form tough membranes or solubilized for use as ionomers in the electrode layers of fuel cells. However, ionomer preparation is not so easy in these systems as cations cluster and the hydrocarbon functionalities may have no gas transport properties.
17:00 | Poster presentation and Coffee
17:30 | Session 4
Modified porous oxides as water-storing additives
for fuel cell membranes
Michael Wark1, Christopher F. Seidler1, Madita Einemann1, Amanda Schlüterbusch2
1 Institute of Chemistry, Chemical Technology 1, Carl von Ossietzky University of Oldenburg,
Carl-von-Ossietzky-Str. 9-11, 26129 Oldenburg, Germany, firstname.lastname@example.org
2 NEXT ENERGY · EWE Research Centre for Energy Technology at the University of Oldenburg,
Carl-von-Ossietzky-Str. 15, 26129 Oldenburg, Germany
In order to widen the possible temperature range of operation for PEM fuel cells, inorganic (solid) additives have attracted attention to reduce the humidity loss at elevated temperatures.[i] Self humidifying composite membranes with hygroscopic inorganic solids, e.g. SiO2 and TiO2, have been developed.[ii] However, the incorporation of modified porous materials as bifunctional inorganic fillers with both hydrophilic and proton conducting properties is even a better approach.
Thus, in the Wark group novel hybrid membranes for PEMFC and AEMFC were formed e.g. by combining proton-conductive SO3H-modified porous silica materials (e.g. Si-MCM-41, KIT-6) with polymers, e.g. Nafion, polysiloxanes or polyoxadiazoles and casting of membranes from these suspensions.[iii] Distribution of the -SO3H-groups in the porous networks was studied and proton conduction paths were analyzed by impedance spectroscopy and PFG-MAS-NMR spectroscopy. We demonstrated that mesoporous SiO2 materials with very narrow channels are advantageous for the modification with SO3H-groups, because protons can hop more easily between -SO3-groups located on opposite sides of a pore channel.[iv] Especially at dry state or low degree of hydration, the density of neighboring proton-conducting groups plays an important role on the proton transfer; sufficiently high densities of -SO3H-groups are best obtainable by the co-condensation synthesis route.[v],[vi] Recently, we demonstrated that hybrid membranes from Nafion and -SO3H-functionalized Si-MCM-41 with the protic ionic liquid (PIL) triethylammonium tri-fluoromethanesulfonate infiltrated into the pores exhibit good mechanical stability and high conductivity up to 1 × 10-2 S/cm at about 150°C.
For application in AEMFC porous SiO2 materials are too unstable, thus for hybrid membranes for this fuel cell type we concentrate on TiO2 and ZrO2 materials with ordered porosity and modify the pores with phosphate and phosphonate groups.
[i] S.P. Jiang, J. Mater. Chem. A 2014, 2, 7637.
[ii] Y.F. Li, G.W. He, S.F. Wang, S.N. Yu, F.S. Pan, H. Wu, Z.Y. Jiang, J. Mater. Chem. A 2013, 1, 10058.
[iii] D. Gomes, R. Marschall, S. P. Nunes, M. Wark. J. Membr. Sci. 2008, 322, 406.
[iv] R. Marschall, I. Bannat, J. Caro, M. Wark, Microporous Mesoporous Mater. 2007, 99, 190.
[v] M. Sharifi, R. Marschall, M. Wilhelm, D. Wallacher, M. Wark, Langmuir 2011, 27, 5516.
[vi] M. Sharifi, C. Köhler, P. Tölle, T. Frauenheim, M. Wark, Small 2011, 8, 1086-1097.
Radiation-grafted anion-exchange polymer electrolytes for alkali membrane fuel cells and electrolysers
Lianqin Wang, Julia Ponce, Rachida Bance-Soualhi, Daniel Whelligan, Emma Cunningham, Emanuele Magliocca,1 Elisabete Santiago,2 William Mustain,3 John Varcoe
University of Surrey
Department of Chemistry, University of Surrey, Guildford, GU2 7XH, United Kingdom
This presentation will describe the latest research at the University of Surrey and the development of anion-exchange membranes (AEM) and ionomers (AEI) for use in alkali membrane fuel cells and electrolysers.4 These anion-exchange polymer electrolytes are produced using the post-irradiation grafted method (PIG). As reported at the previous EMEA 2015 meeting, poly(ethylene-co-tetrafluoroethylene), ETFE, can be used as substrates for radiation-grafted AEMs and AEIs.5
Recent achievements and advancements in this technology (since EMEA 2015) include:
- Synthesis of AEMs with benzyl-type heterocyclic chemistries that are more stable to alkali that the those containing the benzyltrimethylammonium benchmark;
- Synthesis protocols that require reduced radiation doses, reduced amounts of monomer and reduced amounts of non-aqueous solvents;
- Synthesis of thinner PIG-based AEMs;
- The ability to produce PIG-AEMs based on low density polyethylene (LDPE) rather than ETFE;
- Synthesis of an interesting class of PIG-based solid-state AEI powders;
- AEMs with high hydroxide conductivities and high performances in H2/O2 fuel cells
The figure above shows the loss of ion-exchange capacity, Cl content, and N content when benzyltrimethylammonium (PVB-TMA), benzylmethylpiperidinium, and benzylmethylpyrrolidinium ETFE-based PIG-AEMs were treated with aqueous KOH (1 mol dm-3) at 80°C for 28 d.
This research was funded by the Engineering and Physical Sciences Research Council of the UK (grants EP/M005933/1, EP/M014371/1, EP/M022749/1). We also acknowledge the groups of Prof Andrew Herring (Colorado School of Mines, USA, hydroxide conductivities and SAXS data), Prof Lin Zhuang (Wuhan University, P. R. China, fuel cell test data), and Prof William David FRS (University of Oxford and Rutherford Appleton Laboratory, SANS data) for providing the indicated data.
1 Visiting student from Sapienza – Università di Roma, Italy; 2 Visiting postdoc from Instituto de Pesquisas Energéticas e Nucleares, Sao Paulo, Brazil; 3 Visiting Fulbright Scholar from the University of Connecticut, USA (http://www.fulbright.org.uk/about/meet-our-fulbrighters/william-e-mustain/1129); 4 Energy Environ. Sci., 7, 3135 (2014); 5 Energy Environ. Sci., 5, 8584 (2012).
18:30 | Break
19:00 | Conference Dinner
Wednesday June 29th
9:00 | Session 5
Alkaline-stable Anion Exchange Blend Membranes (AEBMs)
from Polyvinylbenzylchloride and Tetramethylimidazole
as the Cationic Head Group
Dr. Jochen Kerres
ICVT – Institute for Chemical Process Engineering Stuttgart, Germany
University of Stuttgart Böblinger Straße 78, 70199 Stuttgart
In this study, synthesis and characterization of novel ionically and covalently cross-linked Anion Exchange Blend Membranes (AEBMs) is described. AEBMs were prepared following procedures recently developed in our group [1,2] by mixing solutions of polyvinylbenzylchloride (PVBCl), tetramethylimidazole (TMIm), polybenzimidazoles (PBI) (F6PBI or PBIOO) and a sulfonated polymer (S-polymer, SAC 098 (a sulfonated poly(phenylethersulfone), nonfluorinated) or SFS 001 (a sulfonated aromatic polyether, partially fluorinated)). To some of the AEBMs a hydrophilic PEG microphase was added with the purpose of increase of ionic conductivity.
During evaporation of the solvent following reactions took place:
- Quaternization of the PVBCl by reaction of a majority of the CH2Cl groups with TMIm
- Covalent cross-link formation by reaction of a minor share of the CH2Cl groups with N-H groups of the PBI
- Ionic cross-link formation between the cationic head-groups of the AEBM and the anionic head-groups of the sulfonated AEBM component
In the AEBMs the PBI component served as mechanically stabilizing blend component.
The membranes were subjected to alkaline treatment in 1M KOH at 90°C for 10 days and longer (one of the membranes was soaked in the alkaline solution for even 30 days) to investigate their alkaline stability. The membranes were characterized before and after alkaline treatment in terms of Cl- conductivity (by impedance spectroscopy in dependence of temperature from room temperature up to 90°C at a r. h. of 90%), thermal stability (by thermogravimetry), and gel content (by extraction with 90°C hot DMAc).
It turned out that the membranes showed good to excellent alkaline stabilities: one of the membranes lost only about 25% of ionic conductivity after 30 days of soaking in 1M KOH at 90°C. All membranes possessed a gel content of more than 90% after extraction with DMAc, indicating complete cross-linking of the AEBMs. Moreover, the membranes showed high Cl– conductivities. Particularly those membranes having an additional PEG microphase had remarkably high Cl– conductivities (e. g. 70 mScm-1@90°C@90% r.h.).
 Novel morpholinium-functionalized anion-exchange PBI-polymer blends. C. Morandi, R. Peach, H. M. Krieg, J. Kerres, J. Mater. Chem. A, 2015, 3, 1110-1120; DOI: 10.1039/c4tA05026f
 Novel Imidazolium-Functionalized Anion-Exchange Polymer PBI Blend Membranes. C. G. Morandi, R. Peach, H. M. Krieg, J. Kerres, J. Memb. Sci. 2015, 476, 256-263; DOI: 10.1016/j.memsci.2014.11.049
10:30 | Poster Presentation and Coffee
11:00 | Panel Discussion
Dr. Alexander Dyck
(NEXT ENERGY, Germany)
12:15 | Lunch
13:45 | Session 6
Anion-conducting polymers and membranes functionalized with quaternary ammonium groups via alkyl spacers
Hai-Son Dang, Thanh Huong Pham, Joel Olsson, Patric Jannasch
Department of Chemistry, Lund University
P.O. Box 124, SE-22100 Lund, Sweden
Different approaches to anion exchange membranes (AEMs) are presently intensively investigated and developed for potential applications in electrochemical energy conversion technologies such as fuel cells and electrolyzes.1 The major challenge in this work is to identify synthetic strategies to membrane materials which combine high hydroxide ion conductivity and good mechanical properties with sufficient long-term chemical and thermal stability.1
We have previously reported on the synthesis of trimethylalkyl ammonium groups attached to poly(phenylene oxide) (PPO) via flexible alkyl spacers.2 AEMs based on these polymers showed a pronounced ionic phase separation, enhanced hydroxide ion conductivity and much improved alkaline stability in comparison to corresponding polymers with trimethylbenzyl ammonium groups conventionally located on the PPO backbone.2,3 This encouraged us to further investigate the influence of the side chain configuration on the AEM properties.4 We have for example prepared and investigated PPOs carrying alkyl spacers with different cationic groups, as well as polyionic chains. Recently, Marino and Kreuer reported on the high alkaline stability of low-molecular weight aliphatic spiro- and monocyclic quaternary ammonium (QA) compounds.5 In contrast to polymers functionalized with N-spirocyclic QA groups6, it is quite straight-forward and inexpensive to prepare polymers with alicyclic QA groups. We have focused our work on PPOs functionalized with mono- and bis-piperidinium groups via alkyl spacers. In addition, membranes crosslinked with alkyl bis-piperidinium chains were prepared in a reactive membrane casting process. In this presentation we will discuss molecular design principles, synthetic procedures and important structure-property relationships of these new AEM materials.
a) N. W. Li, M. D. Guiver, Macromolecules, 2014, 47, 2175; b) J. R. Varcoe, P. Atanassov, D. R. Dekel, A. M. Herring, M. A. Hickner, P. A. Kohl, A. R. Kucernak, W. E. Mustain, K. Nijmeijer, K. Scott, T. W. Xu and L. Zhuang, Energy Environ. Sci., 2014, 7, 3135.
H. S. Dang, E. A. Weiber, P. Jannasch, J. Mater. Chem. A, 2015, 3, 5280.
P. Jannasch, E. A. Weiber, Macromol. Chem. Phys., 2016, 217, 1108.
H. S. Dang, P. Jannasch, Macromolecules 2015, 48, 5742.
M. Marino, K. D. Kreuer, ChemSusChem, 2015, 8, 513.
T. H. Pham, P. Jannasch, ACS Macro Lett., 2015, 4, 1370.
Ion conducting Membranes for Vanadium Flow Battery Application: Research and Development
Huamin Zhang*, Xianfeng Li
Division of energy storage, Dalian Institute of Chemical Physics, Chinese Academy of Science, Zhongshan Road 457, Dalian 11023, Email: email@example.com
Vanadium flow batteries (VFBs) are one of the most promising candidates for large scale energy storage application, due to their attractive features like flexible design, high efficiency, long cycle life and high safety. Exploring new membranes for VFB application is one of most important targets in this field. To address the problem of hydrocarbon ion exchange membranes (poor chemical stability), brought by the introduction of ion exchange groups in polymer, porous membranes, based on the idea of separating vanadium ions from protons via pore size exclusion, have been successfully introduced in VFB recently by our group.
The first reported porous membrane for VFBs is made from hydrolyzed polyacronitrile (PAN). The membranes show good prospects in VFBs, exhibiting columbic efficiency of 95 % and energy efficiency of 76 % at the current density of 80 mA cm-2. To further optimize the membranes selectively and battery performance, the nanofiltration (NF) membranes with in situ assembled silica on the surface and in the pores are prepared. The modified membranes show much higher V/H ion selectively by achieving a CE up to 98 % (EE: 79 %) at the current density of 80 mA cm-2. Later, to further achieve impressive VFB performance, advance charged membranes with highly symmetric spongy structures, formed with a unique stack of closed cells consisting of positively charged ultrathin walls, were specially designed for VFBs via the innovation in both structure and material. The designed membranes combine excellent vanadium ions rejection with high proton conductivity, showing much better performance that of Nafion 115 in a wide operation current density range. Another way to fabricate high performance and ion selectively membranes is to introduce an ultrathin ion selective layer on the porous membrane support. In this way, the pores of the skin layer are kept relatively large to ensure membrane conductivity while the ultrathin top layer will ensure the selectivity and maintain the ion conductivity. The prepared composite membranes show a CE of 98.5 % and EE of 86.5 %, which is much better than commercialized Nafion 115. Quite recently, very impressive results were achieved on the design and fabrication of high performance porous membranes and further upscale was carried out.
In this presentation, the recent progress and challenge of ion conducting membranes in the application of VFB will be demonstrated.
 H. Zhang, H. Zhang, X. Li, Z. Mai, J. Zhang, Nanofiltration (NF) membranes: the next generation separators for all vanadium redox flow batteries (VRBs)?, Energy & Environmental Science, 4 (2011) 1676.
 H. Zhang, H. Zhang, F. Zhang, X. Li, Y. Li, I. Vankelecom, Advanced charged membranes with highly symmetric spongy structures for vanadium flow battery application, Energy Environ. Sci., 6 (2013) 776-781.
 Y. Li, X. Li, J. Cao, W. Xu, H. Zhang, Composite porous membranes with an ultrathin selective layer for vanadium flow batteries, Chemical Communications, 50 (2014) 4596-4599.
 W. Xu, X. Li, J. Cao, H. Zhang, H. Zhang, Membranes with well-defined ions transport channels fabricated via solvent-responsive layer-by-layer assembly method for vanadium flow battery, Scientific reports, 4 (2014).
Ternary polybenzimidazole-based alkaline electrolytes
David Aili, Mikkel Rykær Kraglund, Jens Oluf Jensen
Department of Energy Conversion and Storage, Technical University of Denmark
Kemitorvet 207, DK-2800 Kgs. Lyngby, Denmark
Poly(2,2’-(m-phenylene)-5,5’-bisbenzimidazole) (m-PBI) is the most thoroughly studied derivative in the polybenzimidazole family and is well-recognized for its excellent thermo-mechanical properties, chemical stability and good film-forming-characteristics. In the form of membranes, it can absorb large amounts of aqueous KOH to form an apparent one-phase ternary electrolyte system and its practical feasibility has been demonstrated in e.g. alkaline water electrolyzers, fuel cells, and supercapacitors. The composition of the membrane strongly depends on the concentration of the bulk solution, which in turn determines the physicochemical properties and chemical stability of the membrane. The potassium polybenzimidazolide form of m-PBI (Figure 1) has been found to predominate at KOH concentrations above 15 wt%, where a sharp increase in electrolyte uptake and ion conductivity is observed. This contribution will address fundamental aspects of this class of materials in relation to the practical use as electrolyte in a zero-gap alkaline water electrolyzer.
 J. Yang, R. He and D. Aili, “Synthesis of polybenzimidazoles” in High temperature polymer electrolyte membrane fuel cells: Approaches, Status and Perspectives, eds: Q. Li, D. Aili, H.A. Hjuler, J.O. Jensen, Springer, Cham, Switzerland, 2016, pp. 151-167.
 D. Aili, M.K. Hansen, R.F. Renzaho, Q. Li, E. Christensen, J.O. Jensen, N.J. Bjerrum J. Membr. Sci. 2013, 447, 424-432.
 L. Zeng, T.S. Zhao, L. An, G. Zhao and X.H. Yan, Energy. Environ. Sci. 2015, 8, 2768-2774.
 C. Xu, J. Yan, Q. Qin, Y. Deng, J. Cheng, Y. Zhang and Y. Wu, RSC Adv. 2016, 6, 19826-19832.
 D. Aili, K. Jankova, J. Han, N.J. Bjerrum, J.O. Jensen, Q. Li, Polymer 2016, 84, 304-310.
 D. Aili, K. Jankova, Q. Li, N.J. Bjerrum, J.O. Jensen, J. Membr. Sci. 2015, 492, 422-429.
15:15 | Poster Presentation and Coffee
15:45 | Session 7
Phosphoric Acid-Base HT Fuel Cell Membranes:
What we can learn from Model Systems
Max-Planck-Institute for Solid State Research
Heisenbergstrasse 1, D-70569 Stuttgart, Germany
The proton conducting constituent of PBI-PA (poly-benzimidazole / phosphoric acid) membranes for HT fuel cell applications,  is phosphoric acid, the compound with the highest intrinsic proton conductivity known so far. Considering the very high PA content of such membranes, their conductivity is surprisingly low raising the question which parameters control the proton conductivity including the underlying conduction mechanism of this type of membranes. Transport data and the results of CP-MD simulations of pure phosphorous acids (phosphoric-, phosphonic- and phosphinic acid) strongly suggest that the key to high proton conductivity is “hydrogen bond network frustration”, the consequence of an imbalance of the number of potential proton donors and acceptors. MD-simulations, conductivity and NMR studies on the model system phosphoric acid / benzimidazole (BI) clearly reveal proton transfer from PA to the basic site of BI. This not only reduces the PA hydrogen bond network frustration and therefore proton conductivity, but also the hygroscopicity of PA/BI mixtures compared to this of pure phosphoric acid.,  The latter even further reduces proton conductivity for a given relative humidity (RH). This conductivity loss is mainly the result of a suppression of the conductivity contribution from aqueous species which is suggested to be an important advantage for fuel cell applications since the mobility of aqueous species (three times higher than this of phosphorous species) may lead to electroosmotic water drag, detrimental to the overall membrane conductivity under load. This understanding also provides a natural explanation for the poor performance of Nafion membranes impregnated with phosphoric acid.
 A. Schechter, R. F. Savinell, J. S. Wainright, D. Ray Journal of the Electrochemical Society 156, B283-290, 2009
 J. Mader, L. Xiao, T. J. Schmidt, B. Benicewicz Adv. Polym. Sci. 216, 63, 2008
 K. D. Kreuer Chemistry of Materials 8, 610, 1996
 L Vilciauskas, C. C. de Araujo, K. D. Kreuer Solid State Ionics 212, 6, 2012
 L. Vilciauskas, M. E. Tuckerman, G. Bester, S. J. Paddison, K. D. Kreuer Nature Chemistry 4, 461, 2012
 L. Vilciauskas Solid State Ionics 252, 34–39 2013
 J. P. Melchior PhD-thesis Stuttgart University 2015 http://elib.uni-stuttgart.de/handle/11682/6911
 J. P. Melchior et al. in preparation
 D. Aili, R.F. Savinell, RF, J.O. Jensen, L. N. Cleemann, LN, N.J. Bjerrum, Q. F. Li, QF Chem. Electro. Chem. 1, 1471, 2014
Degradation Mechanism of Non-perfluorinated ion exchange membranes under Vanadium Flow Battery Medium
Xianfeng Li*, Huamin Zhang*
Vanadium flow batteries (VFBs), because of their long life, active thermal management and independence from energy and power ratings, are widely used as large scale energy storage devices. As the key materials of a VFB, an IEM plays the role of separating the positive and negative electrolytes and completing the current circuit by transferring ions. Currently, perfluorinated membranes and non-perfluorinated membranes are the mostly studied membranes in VFBs. One centre problem that hinders the application of perfluorinated membranes in VFBs is their poor ion selectivity together with extremely high cost, although they exhibit high conductivity and excellent chemical stability. Accordingly, non-perfluorinated membranes like sulfonated polyaromatic membranes are suggested as an alternative to perfluorinated membranes in VFBs due to their tunable selectivity and low cost. However, these membranes often suffer from poor chemical stability, further hampering their application. Even though, the study of degradation mechanism is very limited and the detailed degradation reaction of membranes under VFB is not clear due to the complicated medium of VFB (strong acidic, oxidizing and high potential), which leads to very few relevant strategies to synthesize of new materials with excellent performance for VFB application.
Here we report the degradation mechanism of sulfonated poly (ether ether ketone) (SPEEK) cation exchange membranes and poly polyoxadiazole based anion exchange membranes (Figure 1) under VFB medium. Based on this degradation mechanism, strategies to improve the chemical stability of ion exchange membranes will be suggested.
 X. Li, H. Zhang, Z. Mai, H. Zhang, I. Vankelecom, Ion exchange membranes for vanadium redox flow battery (VRB) applications, Energy & Environmental Science, 4 (2011) 1147-1160.
 Z. Mai, H. Zhang, H. Zhang, W. Xu, W. Wei, H. Na, X. Li, Anion-Conductive Membranes with Ultralow Vanadium Permeability and Excellent Performance in Vanadium Flow Batteries, ChemSusChem, 6 (2013) 328-335.
 Z. Yuan, X. Li, J. Hu, W. Xu, J. Cao, H. Zhang, Degradation mechanism of sulfonated poly (ether ether ketone)(SPEEK) ion exchange membranes under vanadium flow battery medium, Physical Chemistry Chemical Physics, 16 (2014) 19841-19847.
Comb-shaped alkyl imidazolium-functionalized polymers as high performance anion-exchange membranes
SangYong Nam and Tae-Hyun Kim*
Gyeongsang National University, 900 Gazwa-dong, Chinju 660-701, Korea
* Incheon National University, Songdo-dong, Yeonsu-gu, Incheon,406-772, Korea
The anion, i.e. OH–, exchange membrane (AEM), is one of the key components of anion exchange membrane fuel cells (AEMFCs), and should possess certain properties, such as high ionic conductivity, low degree of swelling, and high chemical stability.1 A variety of AEMs, whose main polymer chain structures range from poly(arylene ether)s and their analogues, polyimides to poly(phenylene oxide)s have been studied. As anion-conducting groups, ammonium, guanidium, piperazinium, imidazolium, morpholinium and metal cations have been investigated. Among the cations studied, imidazolium-based AEMs have recently drawn particular interest due to their relatively high chemical stability, which is largely attributed to the steric hindrance and the presence of the π-conjugated structures. The conductivity of these cations, including imidazolium, however, is still not yet satisfactory.
In general, the ionic conductivity of ion-exchange membranes including AEMs is determined by two factors: the ionic mobility and the ion-exchange capacity (IEC), defined as the milliequivalents (meq) of conducting groups per gram of polymer. To enhance the OH– conductivity, increasing the IEC seems to be an easier choice than promoting the OH– mobility in the AEM. However, high IEC is inevitably accompanied with excessive water uptake, causing significant swelling of the corresponding membranes. Hence a more efficient strategy to boost the OH– conductivity of AEM is to improve the OH– mobility while keeping the IEC at a moderate level. Such a promotion of the OH– conducting efficiency can only be realized by reinforcing the ionic channel in the AEM.
We have developed alkyl imidazolium-functionalized block copolymers with alkyl chains of lengths varying from C2 to C16 as novel anion-exchange membranes.2 The alkyl imidazolium-functionalized membranes with relatively long alkyl chains (C6 and greater) formed self-aggregated structures due to the introduction of long pendant hydrophobic side chains, which resulted in comb-shaped polymers. The benefit of this comb-shaped system is its high ionic conductivity and simultaneous preserved IEC and hence dimensional stability. The chemical stability of imidazolium further enhanced the alkaline stability of the corresponding membranes. The combination of comb-shaped long alkyl chains, together with the imidazolium group indicate that these membranes are promising candidates as electrolytes for AEM fuel cells.
R. Varcoe, P. Atanassov, D. R. Dekel, A. M. Herring, M. A. Hickner, P. A. Kohl, A. R. Kucernak, W. E. Mustain, K. Nijmeijer, K. Scott, T. Xu and L. Zhuang, Energy Environ. Sci., 2014, 7, 3135-3191.
H. Rao, S.Y. Nam and T.-H. Kim, J. Mater. Chem. A. 2015, 3, 8571-8580.
Vanadium-Air Redox Flow Battery: Membrane Induced Issues
Jan grosse Austing1, Carolina Nunes Kirchner1, Gunther Wittstock2
1 NEXT ENERGY · EWE Research Centre for Energy Technology, Carl-von-Ossietzky-Str. 15, 26129 Oldenburg, Germany
2 Carl von Ossietzky University of Oldenburg, Faculty of Mathematics and Natural Sciences, Center of Interface Science, Institute of Chemistry, 26111 Oldenburg, Germany
A promising approach to improve the energy density of vanadium redox flow batteries is the replacement of the positive half-cell by a bidirectional air electrode, where oxygen (from air) is consumed in discharging mode and water is split while charging.1,2 We recently reported the setup and behaviour of a novel unitised bidirectional vanadium/air redox flow battery comprising a two-layered cathode.3 One layer is a graphite felt modified with IrO2 for the oxygen evolution reaction during charging. The second layer is a gas diffusion electrode loaded with Pt/C for the oxygen reduction reaction. However, the proposed battery concept exhibit significant capacity loss during cycling and comparably low coulombic efficiencies ranging between 55% – 80% in dependence of the operational current density. The insufficient performance is mostly determined by the properties of the ion exchange membrane. ICP measurements of the catholyte indicate that the irreversible capacity loss is related to vanadium ion crossover from the anodic to cathodic cell compartment. Moreover, in-situ UV/VIS measurements show the appearance of self-discharge during the cell operation due to oxygen crossover from the cathodic to the anodic half-cell, causing the oxidation of V2+ species.4 As a consequence, a significant decrease in the columbic efficiency is apparent.
To suppress the vanadium ion and oxygen crossover a modification of Nafion117 membrane via Layer-by-layer (LbL) deposition of polyethylenimine (PEI) and Nafion ionomer is proposed.5 The modified membranes are characterized using various methods such as FTIR spectroscopy, SEM and thermogravimetric analysis (TGA). Moreover, the influence of the LbL modification on the ionic conductivity and species crossover is examined as a function of the LbL deposition iteration. An optimal H+ selectivity was observed for 10 LbL PEI/Nafion layers, which was more than 20 times higher in comparison to the unmodified Nafion 117 membrane. Additionally, a reduction of the oxygen permeability up to 7 % could be obtained. As a result, via utilization of the 10 LbL PEI/Nafion modified Nafion membrane a sufficient columbic efficiency of 93 % could be achieved.
S. S. Hosseiny, et.al., Electrochem. Comm. 13(8) (2011) 751.
C. Menictas, et.al., J. Appl. Electrochem. 41, (2011) 1223.
J. g. Austing et al., J. Power Sources 273 (2015) 1163.
J. g. Austing et al., J. Power Sources 306 (2016) 692.
J. g. Austing et al., J. Membr. Sci. 510 (2016) 259.
17:30 | Closing Words
17:45 | Guided City Tour
JEECS Special Issue
Prospective workshop participants are invited to submit an article to a special issue on “Anion Exchange Membranes and AEM based Systems ”, which will be published in the newly founded Journal of Electrochemical Energy Conversion and Storage (JEECS), which evolved from ASME’s Journal of Fuel Cell Science and Technology.
Manuscripts should be original research papers and can be submitted between February and October 2016 and will be fully peer reviewed. An early submission is encouraged, so that the first accepted articles can already be available online at the time of the workshop. The printed version is planned for the February 2017 issue of the journal.
Participants are invited to submit abstracts for poster presentations to EMEA@next-energy.de until June 6th 2016. The Fuel Cells Bulletin grants an award for the best poster presented at the workshop.
Dr. Wiebke Germer – NEXT ENERGY · EWE Research Centre for Energy Technology (Germany)
Dr. Dirk Henkensmeier – Korea Institute of Science and Technology (KIST, South Korea)
Prof. Artur Michalak – Jagiellonian University in Krakow (Poland)
The participation fee of €380 is payable after receipt of invoice. For registration please complete the “Workshop Registration Form” and submit it by fax or email to NEXT ENERGY by June 1st 2015.
Due to the limited number of participants, registrations are considered in order of receipt.
EWE-Forschungszentrum für Energietechnologie e. V.
Carl-von-Ossietzky-Str. 15 | 26129 Oldenburg | Germany
Phone: +49 441 99906-319
Fax: +49 441 99906-109
The spa town Bad Zwischenahn is located in the north-west of Germany and is a famous recreational area because of its colorful flowering rhododendron shrubs and park-like landscape. The city can be reached conveniently by train or by car. Bremen Airport is located nearby.
The Workshop will be held at the conference and golfing hotel “Hansens Haus am Meer“, which is located directly in the spa gardens at the lake “Zwischenahner Meer”, the third largest lake in Lower Saxony.
Bad Zwischenahn has a range of hotels in a variety of price categories. Rooms can also be booked at the conference hotel „Hansens Haus am Meer“.
The nearest international airport is Bremen, which is 60 km from Bad Zwischenahn.
The “Hansens Haus am Meer” hotel offers a free shuttle service from the train station to the hotel on request.
- Coming from Bremen (A28): Follow the A28 autobahn in the directions for Oldenburg / Emden / Leer. In Oldenburg, at the interchange “Oldenburg West“ continue to Emden / Leer on the A28. Leave the autobahn at the exit ramp No. 9 “Neuenkruge” and follow the road signposts to Bad Zwischenahn.
- Coming from Leer / Netherlands (A31): Change to the A31 autobahn at the “Leer” junction and follow the A28 in the direction for Oldenburg. Leave the autobahn at the exit ramp No. 8 “Zwischenahner Meer” and follow the road signs to Bad Zwischenahn.
The conference fee of €380 includes the lab tour, lunch and coffee breaks on both days as well as the Get-together on Monday evening and the conference dinner on Tuesday evening and the VAT. Also covered is the bus tour to the NEXT ENERGY research centre.
NEXT ENERGY – EWE-Forschungszentrum für Energietechnologie e. V. may charge an administration fee of EUR 70.00 for any change or cancellation of registration. Cancellation must be received by NEXT ENERGY in writing up until seven days prior to the event. Cancellations received after this date will be charged the full fee.
The program is subject to amendment. In the unlikely event of it being cancelled for reasons beyond the control of NEXT ENERGY, registration fees already paid will be refunded.