Fuel Cells | Workshop EMEA2018

Workshop on Ion Exchange Membranes for Energy Applications – EMEA2018

26 – 28 June 2018 in Bad Zwischenahn (Germany)

60 participants from 15 countries made the last EMEA-workshop in June 2017 a success. The coming EMEA2018 Workshop will be the 6th workshop in this series. Material developments and ion exchange membrane based systems for energy applications will be discussed by representatives from research and industry with the focus set on anion exchange membranes. In addition to invited and contributed talks, the workshop features a panel discussion, in which experts from academia and industry will discuss the development of the field. A poster exhibition offers scientists and especially young researchers and students the opportunity to present their work. A price for the best poster will be awarded. A guided tour through the DLR Institute of Networked Energy Systems (former NEXT ENERGY) research laboratories, a get-together and a conference dinner will provide additional opportunities for lively scientific exchange in a familiar atmosphere.

AGENDA

Tuesday June 26th

20:00 | Get-together

Wednesday June 27th

8:30 | Opening Reception Desk

9:00 | Welcome

9:15 | Session 1

       

 

 

 

Focusing on the main challenges of the anion exchange membrane fuel cell technology

Dario R. Dekel

Technion – Israel Institute of Technology
Haifa, Israel
dario@technion.ac.il

 

After a few years of intensive research, recent studies of Anion Exchange Membrane Fuel Cells (AEMFCs) finally show cell performance at the required levels for automotive applications. This achievement was mainly due to the successful development of anion exchange membranes (AEMs) with considerable high hydroxide conductivity (100 mS cm-1 and above). Based on these high performance membranes, AEMFCs with power densities and limiting current densities higher than 1 W cm-2 and 4 A cm-2 have been recently achieved, which only a couple of years ago seemed far from possible. In order to make the next breakthrough and bring the AEMFC technology to the next levels, the following challenges need to be addressed: (A) the need for Pt-free (and PGM-free) catalysts highly active towards hydrogen oxidation reaction in alkaline medium, (B) carbonation issues while working with ambient air feed, and (C) barriers in cell performance stability. The TEEM lab at Technion is focusing its activities on these (and other) topics, aiming to make a significant impact in the AEMFC research community. Latest achievements of the TEEM lab in these AEMFC challenging fronts will be presented and discussed during the talk.

*from “Review of cell performance in anion exchange membrane fuel cells”;

Dario R. Dekel; J. Power Sources 375, 158-169, 2018

Polyimidazolium Anion Exchange Membranes

Steven Holdcroft, Jiantao Fan, Andrew G. Wright, Benjamin Britton, Thomas Weissbach, Thomas J. G. Skalski, Jonathan Ward, Timothy J. Peckham, Eric Schibli+, Barbara Frisken+

Simon Fraser University
Department of Chemistry, Department of Physics+,  8888 University Drive, Burnaby, Greater Vancouver, BC, V5A 1S6, Canada
holdcrof@sfu.ca

 

Cationic polyelectrolytes possess cationic groups as either a pendent functionality or integral to the main chain. In recent years, the study of cationic polymers possessing hydroxide counter ions have gained prominence. However, organic-based polymer cations are prone to nucleophilic attack by hydroxide ions, destroying the anion-exchange capacity and hydroxide ion conductivity. Numerous cationic head groups are being explored with a view to increasing the stability of cationic polymers in highly basic media. Despite rapid advancements, cationic polymers stable in caustic solutions at elevated temperatures have proved elusive.

In this presentation, we report on poly(arylene-imidazoliums), which were synthesized by microwave polycondensation of dialdehyde with bisbenzil and quantitatively functionalized by alkylation. This cationic polyelectrolyte is sterically protected around the C2-position and possesses a t1/2 of >5000 h in 10 M KOHaq at 100 ˚C. Alkaline stability is rationalized through analyses of model compounds, single crystal x-ray diffraction, and density functional theory. The polyelectrolytes form tough, pliable, transparent, anionically conductive films.

10:15 | Poster Presentation with Coffee and Snacks

10:45 | Session 2

Polyethylene-based radiation-grafted anion-exchange membranes for development of alkali membrane fuel cells

John R Varcoe, Lianqin Wang

Department of Chemistry, The University of Surrey,
Guildford, GU2 7XH, United Kingdom
j.varcoe@surrey.ac.uk

 

This presentation will discuss the latest developments of polyethylene-based (e.g. low density polyethylene – LDPE) radiation-grafted anion-exchange membranes (RG-AEM) being targeted at application in alkaline membrane fuel cells (AMFC). Evidence will be presented of high anion conductivities, high fuel cell performances (when used in combination with ETFE-based anion-exchange ionomer powders), and promising alkali stabilities. The scheme below outlines the general synthesis the RG-AEMs that will be discussed.

The figures above show: (left) the H2/O2 AMFC performances at 80 °C (PtRu/C anodes along with the stated cathode electrocatalysts) of an RG-AEM made from 15 µm thick LDPE film and (right) the change in hydroxide anion conductivity of the same RG-AEM over a period of 500 h.

Creating Co-continuous Morphologies in Polymers for Anion Exchange Membranes

Frededrick L Beyer

U.S. Army Research Laboratory
Aberdeen Proving Ground, Maryland, USA
frederick.l.beyer3.civ@mail.mil

 

Anion exchange membranes (AEMs) for use in alkaline fuel cells (AFCs) generally suffer from a combination of shortcomings in conductivity, durability, dimensional stability, and chemical stability. In this program, we have explored a strategy to address three of these requirements simultaneously through control of morphological behavior. Morphological behavior, including form, orientation, and continuity, is expected to have significant effects on conductivity. We seek to create materials that have co-continuous morphologies combining charged, hydrophilic domains for charge transport, and rigid hydrophobic domains for mechanical reinforcement and dimensional stability. Using trimethylamine as a model cation, reaction-induced phase separation was used to create polymer films with co-continuous morphologies and tunable mechanical behavior. This process generates a crosslinked, microphase separated film in one step through the reaction of copolymer of cationic block and a norbornene-functionalized block is reacted with cyclooctene (CO) and dicyclopentadiene (DCPD) to create. The resulting films were found to have excellent conductivity and reasonable mechanical properties. Mechanical properties can be modified by adjusting the relative amounts of CO and DCPD, and by adjusting the molecular weight of the cation-containing block copolymer. Subsequent efforts to improve mechanical properties and chemical stability, as required for device lifetimes, will also be described.

Electrolyte management at VRFB using anion-exchange-membranes

Bernd Bauer, Tomas Klicpera, Karsten Reinwald, Michael Schuster

FUMATECH BWT GmbH
Carl-Benz-Str. 4, 74321 Bietigheim-Bissingen, Germany
bernd.bauer@fumatech.com

 

With the development of polymer electrolyte fuel cells for stationary and mobile application, the interest in new ion-exchange membranes has drastically increased. Most of this work, however, was dedicated to hydrocarbon type and fully fluorinated cation-exchange membranes. The main market for anion-exchange membranes is realised with donnan dialysis for acid recovery today.

The decarbonization of energy markets, will create new applications for anion-exchange membranes. Applications in energy conversion (AEMFC), in chemical energy storage (AEME, RFB) but also in salt gradient batteries and in acid-base batteries using bipolar membranes but even the electrolytic CO2-conversion to E-Fuels justify all current intense R&D in anion-exchange ionomers and membranes.

This presentation will focus on the most relevant and fast growing market for anion-exchange membranes in today’s All-Vanadium-Redox-Flow Batteries.

Despite of all encouraging R&D on new electrolytes for RFB, such as all-organic RFB, complex-metal RFB and alkaline metal RFB, the all vanadium RFB is still dominating the market. The critical factors of VRFB are described with the high CAPEX (due to electrolyte cost), the round-trip efficiency and the capacity fade and self-discharge of the electrolyte on operation.

Using highly selective cation-exchange membranes, the cross-over of vanadium and the resulting imbalance of electrolytes could be reduced but not fully avoided. Therefore, all batteries based on CEM will need a remixing system of high additional cost causing operational losses. Operating the VRFB on anion-exchange membranes at concentrations above the donnan potential of the ionomer, the electrolyte management does change drastically. The vanadium cross-over will be replaced by electrolyte transfer and remixing tanks by a relevelling technology with constant operation of the battery without any visible capacity fade for many years and thousands of charge-discharge cycles.

The symbiosis of membrane chemistry and electrochemical engineering can guarantee robust operation of small and large size batteries. The sterically protected partially fluorinated polyvinylpyridines of the FAP-series membranes have shown proven stability for more than 10 years in VRFB. These FAP-membranes are available with an equivalent weight ranging from 300 to 700 both reinforced or in plain film form. The thickness for stationary small pockets cells could be as low as 2µm. The thickness of woven reinforced membranes for larger stacks could be as high as 75µm.

The use of either by-pass capillaries or porous capillaries in the cell frame guarantee relevelling of the electrolyte without parasitic currents at current densities of 150 mA/cm2. In addition, an increased resistance on discharge at high SOC is repressed by the capillary technology even when the cell is charged to an open-circuit voltage of 1,57 V.

12:15 | Lunch

13:45 | Guided Tour through the Laboratories of the DLR Institute of Networked Energy Systems, Oldenburg

16:00 | Session 3

Technical Targets for Membranes in Alkaline Electrolysis: Translating ex-situ Properties into in-situ Performance

Dr. Artjom Maljusch, Oliver Conradi, Patrick Borowski

Evonik Creavis GmbH
Paul-Baumann-Str. 1, 45772 Marl
artjom.maljusch@evonik.com

 

With the transformation from fossil-based energy generation to renewables, electrolytic hydrogen will play a key role. One limiting factor to widespread adoption of electrolysis for hydrogen production and energy storage are the specific investment costs of PEM-based systems. However, membrane electrolysis under alkaline operation enables elimination of expensive components while keeping many operational advantages of PEM systems. Even though the research efforts on OH-conducting polymers and membranes have been increased significantly in recent years there is still no concept with commercial maturity.

This presentation wants to derive some generic design rules and performance indicators how to translate intrinsic membrane properties systematically into in-situ performance. This holistic approach can provide a guideline for both academics and industry to better synchronize materials development with system requirements and vice versa.

Improved All-Vanadium Redox Flow Batteries with Catholyte Additive and a PBI Anion Exchange Membrane

Ruiyong Chen,a Dirk Henkensmeierb

aTransfercenter Sustainable Electrochemistry, KIST Europe and Saarland University
66123 Saarbrücken, Germany

bFuel Cell Research Center, Korea Institute of Science and Technology (KIST)

02792 Seoul, Korea
e-mail: r.chen@kist-europe.de, henkensmeier@kist.re.kr

 

The utilization of renewable energy resources such as wind and solar energy is in urgent demand. Energy storage devices using all-vanadium redox flow batteries have merits of high safety, long cycle life and flexible system design.[1,2] Electrolytes and membranes play critical roles for overall performance such as cycling efficiencies, capacity retention over cycling.[3-5] Herein, through modifying the commercial vanadium catholyte by adding additives, and through using a crosslinked and methylated meta-PBI membrane (Fig. 1a),[5,6] we have improved largely the Coulombic, voltage and energy efficiencies, in comparison with a commercial Nafion membrane (Fig. 1b,c).[7]

Fig. 1 (a) A crosslinked and methylated meta-PBI membrane,[5] (b) Coulombic (CE), voltage (VE) and energy efficiencies (EE) of an all-vanadium redox flow battery with commercial electrolyte and Nafion 212 membrane, (c) Cycling efficiencies of an all-vanadium redox flow battery with catholyte additive and a PBI anion exchange membrane.

Reference:

[1] R. Ye, D. Henkensmeier, S.-J. Yoon, Z. Huang, D.-K. Kim, Z. Chang, S. Kim, R. Chen, “Redox flow batteries for energy storage: a technology review”, J. Electrochem. En. Conv. Stor. 2018, 15, 010801.

[2] R. Chen, S. Kim, Z. Chang, Chapter: “Redox flow batteries: fundamentals and applications”, Redox: Principles and Advance Applications, M.A.A. Khalid (Ed.), 2017, InTech, pp. 103-118.

[3] R. Chen, R. Hempelmann, Electrochem. Commun. 2016, 70, 56-59.

[4] Y. Zhang, R. Ye, D. Henkensmeier, R. Hempelmann, R. Chen, Electrochim. Acta 2018, 263, 47-52.

[5] Z. Chang, D. Henkensmeier, R. Chen, ChemSusChem 2017, 10, 3193-3197.

[6] T. Weissbach, A.G. Wright, T J. Peckham, A.S. Alavijeh, V. Pan, E. Kjeang, S. Holdcroft, Chem. Mater. 2016, 28, 8060-8070.

[7] R. Chen, D. Henkensmeier, et al., in preparation.

MnO2 as effective OER catalyst for Alkaline Anion Exchange Membrane Electrolysers

Mohamed Mamlouk*, Gaurav Gupta

Newcastle University
Newcastle upon Tyne, United Kingdom- NE1 7RU
mohamed.mamlouk@ncl.ac.uk

Hydrogen is a promising fuel and energy storage solution,  due to its highly efficient conversion between H2 and electricity and good energy density in comparison to most batteries. However, 95 % of the hydrogen is generated from non-renewable sources and 5% from electrolysis due to high cost of these systems[1,2]. Around 50% of the cost of the electrolyser system comes from the precious metal catalyst used in proton exchange membrane system due to acidic environment[3,4]. However, if alkaline anion exchange membrane water electrolyser AAEMWE is used, non-precious metal can be used for catalyst, flow fields and bipolar plates, reducing the cost significantly. It is estimated that replacement of PEM electrolysers wth AAEM electrolysers offers a 43% reduction in cell stack [5]

Oxygen evolution reaction (OER) catalysts which is the slowest of the reaction in the electrolyser systems and thus require more attention. Higher performances can be achieved using high alkaline concentration feed but this in turn reduces the lifetime of the system due to degradation of AEM membrane/ionomers. Thus in order to reduce the degradation and improve the lifetime, low alkaline concentration should be used as feed solution for AEMWE i.e. deionised water. We have shown previously [4] that a current density of 100 mA cm-2 at 1.65V using NiCo2O4 for OER could be achieved at 60 °C [4]. The current research is focused on MnO2 as very effective OER catalyst in the alkaline anion exchange membrane electrolyser. The catalyst has been characterized using XRD and SEM. Using low cost LDPE based membranes radiation grafted AEM, a very promising performance electrolyser was obtained of 1.57 V at 100 mA cm-2 and  a current density of 1 A cm-2 at a potential of 1.78 V in 0.01 M NaOH at 60 °C (Figure 1).

Figure 1: Polarisation curve of MnO2 in 0.01 M NaOH solution at different temperature.

 

References:

[1]                  Y. Cheng, S. P. Jiang, Progress in Natural Science: Materials International 2015, 25.

[2]                  M. N. Manage, D. Hodgson, N. Milligan, S. J. R. Simons, D. J. L. Brett, International Journal of Hydrogen Energy 2011, 36.

[3]                  S. Satyapal, C. Ainscough, D. Peterson, E. Miller, in Hydrogen Production Cost from PEM Electrolysis, DOE Hydrogen and Fuel Cells Program Record, Department of Energy, United States of America, 2014.

[4]                  G. Gupta, K. Scott, M. Mamlouk, Journal of Power Sources 2018, 375, 387.

[5]                  http://www.itm-power.com/wp-content/uploads/2012/04/CaseStudy4-ReducingCostOfHydrogenProduction.pdf

17:10 | Poster Presentation with Coffee and Snacks

17:30 | Session 4

Amphoteric Membranes with Bilayer Architecture for
Vanadium Redox Flow Batteries

Lorenz Gubler1, Fabio J. Oldenburg1, Thomas J. Schmidt1,2

1 Electrochemistry Laboratory, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
2 Laboratory of Physical Chemistry, ETH Zürich, 8093 Zürich, Switzerland
lorenz.gubler@psi.ch

 

Redox-flow batteries are electrochemical energy storage devices aimed at grid-scale applications, for instance for time-shifting storage. They comprise an electrochemical converter and an external tank to store the electrolytes containing redox-active species. The all-vanadium redox flow battery (VFB) uses vanadium-ions in different oxidation states as redox-active species in the two electrolytes, thus irreversible contamination of electrolytes by cross-mixing is avoided. Nevertheless, transfer of vanadium ions across the membrane is to be avoided to minimize faradaic losses. Moreover, dissimilar rates of crossover of the 4 vanadium species can lead to electrolyte imbalance and, thus, capacity fading of the battery.

Here, we present a bilayer membrane concept consisting of Nafion® 212 that is laminated with a thin layer of meta-polybenzimidazole (mPBI). In the sulfuric acid based electrolyte of the VFB, the benzimidazole units of the PBI are protonated, thus forming an anion exchange polymer. The resulting membrane therefore has amphoteric character. Amphoteric membranes have previously shown to have promising properties for VFBs [1], combining the advantages for cation exchange and anion exchange membranes. The net vanadium transfer in this type of ionomer membrane is much more balanced (Figure 1) compared to pure cation or anion exchange membranes and, as a result, the capacity fading can be significantly reduced. Depending on the current density, the net vanadium flux across the membrane can be completely suppressed.

Figure 1, Left: Net vanadium flux (– ® +) over 50 charge/discharge cycles across bilayer Nafion® NR212 / PBI membranes with different PBI-layer thickness at various current densities (40, 80, 120 and 160 mA∙cm-2). Right: Schematic illustration of the Nafion-PBI bilayer membrane.

Reference:
1. F.J. Oldenburg, T.J. Schmidt, L. Gubler, J. Power Sources 368 (2017) 68

Performance and Long-Term Stability of Ionomeric Components
in Anion Exchange Membrane Fuel Cells

Julian Behnken, Janine Leppin, Lukas Mues, Holger Janßen, Kevin Obermann,
Corinna Harms, Alexander Dyck

DLR Institute of Networked Energy Systems
Carl-von-Ossietzky-Str. 15, 26129 Oldenburg, Germany
julian.behnken@dlr.de

 

The anion exchange membrane fuel cell (AEMFC) has recently received increasing attention. In principle it allows the use of non-precious metal catalysts thanks to the high pH of the electrolyte, which reduces significantly the cost in fuel cell systems. Through the development of new materials the performance of AEMFC has increased substantially enabling competition with proton exchange membrane fuel cell regarding beginning of life performance. However, the long-term stability of AEMFC is one of the remaining challenges for this technology.1, 2

Crucial components in the AEMFC are the anion exchange membrane (AEM) as well as the anion exchange ionomer (AEI). While its hydroxide (OH) conductivity has reached satisfying values, the most critical issue is that the functional groups of the membrane, typically based on quaternary ammonium (QA), decompose due to the presence of the highly nucleophilic OH.3 The alkaline stability of QA cations is typically studied by ex-situ tests over time at various OH concentrations or temperatures.4 However, results from ex-situ test often differ from measurements at single cell level in membrane electrode assemblies (MEA) since these tests do not represent real conditions under fuel cell operation. This highlights the need of stability studies at single cell level in MEAs as well as characterization techniques that simulate AEMFCs in operation.5, 6

In this contribution, the AEM and AEI will be characterized in MEAs allowing the evaluation of the performance and stability under fuel cell conditions. By employing an automated spray coating device the reproducibility of the catalyst loading has been improved. Thus comparative studies of equivalent MEAs are possible. Further, test protocols are applied triggering accelerated degradation of ionomeric components by the distinct application of harsh conditions. Electrochemical impedance spectroscopy gives insight to possible degradation pathways. Morphological changes can be determined with micro-computed tomography and scanning electron microscopy. Finally, specific degradation products of the AEM and AEI in the product water are detected by ion chromatography. This combination of measurements under AEMFC conditions and excellent analytical tools contributes to a more comprehensive understanding of AEMFC long-term stability.

References:

  1. S. Gottesfeld, D. R. Dekel, M. Page, C. Bae, Y. Yan, P. Zelenay and Y. S. Kim, J. Power Sources, 2018, 375, 170-184.
  2. D. R. Dekel, J. Power Sources, 2018, 375, 158-169.
  3. 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. Xu and L. Zhuang, Energy Environ. Sci., 2014, 7, 3135-3191.
  4. M. G. Marino and K. D. Kreuer, ChemSusChem, 2015, 8, 513-523.
  5. K.-D. Kreuer and P. Jannasch, J. Power Sources, 2018, 375, 361-366.
  6. D. R. Dekel, S. Willdorf, U. Ash, M. Amar, S. Pusara, S. Dhara, S. Srebnik and C. E. Diesendruck, J. Power Sources, 2018, 375, 351-360.

18:30 | Break

19:00 | Conference Dinner

Thursday June 28th

9:00 | Session 5

Mesoscale Simulations of Anion Exchange Membranes

Stephen J. Paddison, Xubo Luo, Hongjun Liu,

Department of Chemical & Biomolecular Engineering
University of Tennessee, Knoxville, TN 37996, U.S.A.
spaddison@utk.edu

 

The hydrated morphology of anion exchange membrane is a key aspect in determining the ion conductivity. Here we examine changes in the morphology of polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) functionalized with alkyl-substituted quaternary ammonium groups. The effects of the degree of functionalization, percentage of styrene and butyl spacer in the functional side chain were studied with dissipative particle dynamics (DPD) simulations. As anticipated, the results morphology controlled by both the degree of hydration and degree of functionalization. Perfect lamella, imperfect lamella, and non-regular structures were all observed under the various conditions. Among the three types, the imperfect lamella was made up of slices or subdomains of perfect lamella. These lamellae formed in different directions and were interconnected by the transitional regions. The hydrophilic phase swelled with hydration at each degree of functionalization. Domains of exclusive water were formed at the highest water contents (l º nH2O/SO3H = 16 or 20). An analysis of the cluster of water beads showed that percolation of the water may occur when the hydration level reaches about (l = 12). Lowering the functionalization of quaternary ammonium groups may postpone the formation of large connected water domains. Systems with the lower percentage of styrene did not form perfect lamella, but rather imperfect lamella and micelles were found at high hydration levels. With a butyl linker between the backbone and functional group, a perfect lamella morphology was formed at intermediate hydration levels. No perfect lamellae were formed with the butyl grafted as a tail. The butyl spacer appeared to reduce the swelling of the polystyrene blocks probably due to its hydrophobicity.

Figure Coarse-grained model of quaternary ammonium SEBS showing distinct spacer/tail on the TMA+. The block-to-block ratio of the copolymer is 8:152:8 for 17% mol. (30% wt.) as the primary, while 8:288:8 for 10% mol. as the variant.

Using X-ray Computed Tomography for Studying
Alkaline Exchange Membrane Fuel Cells

Iryna V. Zenyuk

Liquid-water management is critical to commercialize alkaline exchange membrane fuel cells (AEMFCs). Water is produced by hydrogen oxidation reaction on the anode side and is needed as a reactant in oxygen reduction reaction (ORR) on the cathode side. Not only anode flooding presents a problem but also cathode dehydration [1, 2]. Optimizing water transport and removal from the cell requires a careful material design considerations and also operating conditions. Two-phase water transport inside the membrane electrode assembly, especially during operation, is complex and requires detailed knowledge of catalyst layer morphology and transport properties. Moreover, it is necessary to know interplay between pressure- and capillary-driven liquid water transport and phase-change induced flow due to evaporation/condensation.

Bridging understanding across nano- and micro-scales is crucial, as water is formed in nano-pores of the catalyst layers and is transported through larger pores in the gas diffusion layers. Synchrotron X-ray computed tomography (CT) is a fast, 3D, non-intrusive technique that allows quantification of morphological properties within porous media. Micro X-ray CT is useful tool for observation ex-situ morphology and also operando experiments with 1.3 um resolution, whereas nano X-ray CT is used to probe finer structures of the catalyst layer with the resolution of 60 nm. In this presentation we will show morphology of novel PGM electrodes and operando water distribution in the cells under varied current densities. As a comparison we will also show X-ray CT of PGM-free electrodes and unique to them water distribution profiles[3].

 

References

[1] H.-S. Shiau, I.V. Zenyuk, A.Z. Weber, J Electrochem Soc, 164 (2017) E3583-E3591.

[2] A. Serov, I.V. Zenyuk, C.G. Arges, M. Chatenet, Journal of Power Sources, 375 (2018) 149-157.

[3] S. Kabir, K. Lemire, K. Artyushkova, A. Roy, M. Odgaard, D. Schlueter, A. Oshchepkov, A. Bonnefont, E. Savinova, D.C. Sabarirajan, P. Mandal, E.J. Crumlin, I. Zenyuk, P. Atanassov, A. Serov, Journal of Materials Chemistry A, (2017).

Nickel-based Anode Electrocatalysts for AEM Fuel Cells  

Plamen Atanassov, Aaron Roy, Morteza R. Talarposhti Kateryna Artyushkova, and Alexey Serov

Center for Micro- Engineered Materials (CMEM) and Chemical & Biological Engineering Department,

Advanced Materials Laboratoty, University of New Mexico, Albuquerque, NM 87131

plamen@unm.edu

 

Over the last decade UNM has been involved in the design of Platinum Group Metal-free (PGM-free) anode catalysts for the emerging field of Alkaline Membrane Fuel Cells (AMFC). Initial effort was directed towards catalysts for selective hydrazine oxidation.1-3 These series materials were based on allowing Ni with oxophillic metal (Zn, La, etc.) to enhance hydrazine dehydrogenation step in contrast to N-N bond splitting as a base for much desired catalyst selectivity.4,5 Successful integration of such catalysts in AEMFCs resulted in the demonstration of highly durable direct hydrazine hydrate liquid fuel-fed fuel cell for automotive applications by Daihatsu Motor Co., with UNM as a part oft the catalysts design team. 6

These Ni-based electrocatalysts were further designed to include Ni alloys with refractive metals7 (Mo, W, Cr) and demonstrated exceptional dehydro-genation selectivity, thus creating the base for the development hydrogen oxidation catalysts in alkaline media. Ni-based electrocatalysts were synthesized as nanoparticles supported on various carbon blacks and modified carbon blacks with loadings of up to 50 % wt. (see Figure A & B). Synthesized martials were comprehensively characterized by physical-chemical methods: XRD, BET, SEM, TEM and XPS. Electrochemical activity of the catalysts was studied with Rotating Disk Electrode (RDE) technique and in a single membrane electrode assembly (MEA) AMFC. MEA design was optimized with respect to critical fabrication parameters such as: catalyst layer thickness (loading), catalyst-to-ionomer ratio, and catalyst deposition as Catalyst Coated Membrane (CCM) vs. gas-diffusion electrode (GDE). It was found that NiMo/C electrocatalyst has a mass activity similar to palladium supported on carbon.8

The MEA performance obtained in H2/O2 single MEA fuel cell tests using Tokuyama membrane and ionomer reached a peak power density higher than 120 mW.cm-2 at relative humidity (RH) of 70 %. When Ni0.9Cu0.1, supported on Ketjenblack, catalysts was used (see Figure C), a record high peak power density was demonstrated: up to 350 mW.cm-2. These new nickel-transition metal alloy catalysts are being studied in detail by spectroscopy and modeled by DFT to establish relevant structure-to-property correlation and demonstrate their utility in H2/O2 AEMFC.

Acknowledgement: DOE-EERE FCTO, Incubator Program DE-EE0006962 “Development of PGM-free Catalysts for Hydrogen Oxidation Reaction in Alkaline Media” (Alexey Serov, PI).

 

  1. U. Martinez, et al., Physical Chemistry and Chemical Physics, 14 (2012) 5512-5517
  2. T. Sakamoto, et al., Journal of Power Sources, 234 (2013) 252-259
  3. A. Serov et al., Angewandte Chemie, Int. Ed., 126 (2014) 10419-10715
  4. T. Sakamoto, et al., Journal of Power Sources, 247 (2014) 605-611
  5. T. Sakamoto, et al., Electrochimica Acta, 163 (2015) 116-122
  6. T. Sakamoto et al., Journal of Power Sources, 375 (2018) 291-299
  7. T. Asset et al., Electrochimica Acta, 215 (2016) 420-426
  8. S. Kabir et al., Journal of Materials Chemistry A, 5 (2017) 24433-24443

10:30 | Poster Presentation with Coffee and Snacks

11:00 | Panel Discussion

  • Moderation:
    Dr. Alexander Dyck
    (DLR Institute of Networked Energy Systems, Germany)

 12:15 | Lunch

13:45 | Session 6

Catalysts, Membranes, CO2 and Water: Requirements and Pathways for High Performing AEMFCs

William Mustain

Department of Chemical Engineering, University of South Carolina
301 Main Street; Columbia, SC 29208
mustainw@mailbox.sc.edu

 

In recent years, advances in alkaline exchange membrane fuel cells (AEMFCs) with anion exchange membrane (AEM) solid polymer electrolytes have gained traction due to their distinct – and potentially game-changing – advantages over proton exchange membrane fuel cells.  However, AEMs and AEMFCs are at a significantly less mature stage in their developmental than proton exchange membrane fuel cells (PEMFCs), and have experienced limitations specifically in the area of stability, carbonation, and achievable current and power densities, exhibiting a sizable performance gap vs PEMFCs.  This talk will focus on several fundamental and engineering advances that have enabled the creation of AEMFCs that are able to achieve ca. 2 W∙cm-2 peak power and 100’s of hours of stable operation, bringing AEMFCs much closer to the incumbent PEMFC technology, and opening the way to overcome the cost and reliability barriers that have slowed the growth and large scale market implementation of AEMFCs.

The three largest challenges facing AEMFCs today are: 1) understanding and controlling the water distribution in operating AEMFCs.  Water dynamics in these cells will be a primary theme of this presentation; 2) mitigating the negative influence of carbonation from atmospheric CO2 when using air as the oxidant.  The carbonate/bicarbonate formation and self-purging mechanisms will be discussed; and 3) reducing the platinum group metal (PGM) loading in the catalyst layers.  Strategies that included both PGM-free and low PGM (~0.1 mg∙cm-2) catalyts will be explored.  The overarching goal of this talk is not only to show the audience the state-of-the-art is in the field, but to also talk them through the mentality of our group in solving these problems and to provide some guidance regarding the approaches that have shown the most promise to date.

For more information about this project and the rest of our group, please visit https://www.mustainlab.com

Partially Fluorinated Aromatic Anion Exchange Membranes:
Effect of Ammonium Structure

Kenji Miyatake, Ahmed Mohamed Ahmed Mahmoud, Kanji Otsuji, and Makoto Uchida

Clean Energy Research Center

4 Takeda, Kofu, Yamanashi 4008510, Japan

miyatake@yamanashi.ac.jp

 

Anion exchange membrane fuel cells (AEMFCs) provide advantages over proton exchange membrane fuel cells (PEMFCs) including possible use of nonprecious metals as electrocatalysts and faster kinetics of the oxygen reduction reaction under alkaline conditions than acidic conditions. While a large number of technical efforts have been made to develop better functioning AEMs, the existing AEMs are still not as conductive and stable as state-of-the-art PEMs. The critical issues for AEMs are mainly related with the instability of the quaternary ammonium groups as well as the polymer main chain in strongly alkaline conditions.

Recently, we found that the absence of heteroatom linkages (e.g., ether and sulfone) in the polymer main chain contributed to improving the alkaline stability of AEMs.1 Introducing perfluoroalkylene groups provided the ammonium functionalized aromatic polymers with good membrane forming capability and flexibility. In addition, we confirmed that pendant ammonium groups separated from the polymer main chains with interstitial hexylene groups improved alkaline stability of the membranes.2 In this presentation, we focus on the effect of ammonium structure on the membrane properties. The ammonium structures include side chain length and cyclic/acyclic groups.3-5 Phase-separated morphology, water affinity, hydroxide ion conductivity, chemical and mechanical stability, and fuel cell performance and durability will be discussed.

 

  1. Ono, J. Miyake, S. Shimada, M. Uchida, K. Miyatake, J. Mater. Chem. A, 3, 21779-21788 (2015).
  2. Ono, T. Kimura, A. Takano, K. Asazawa, J. Miyake, J. Inukai, K. Miyatake, J. Mater. Chem. A, 5, 24804−24812 (2017).
  3. M. A. Mahmoud, A. M. M. Elsaghier, K. Miyatake, Macromolecules, 50, 4256-4266 (2017).
  4. Akiyama, N. Yokota, K. Otsuji, K. Miyatake, Macromolecules, 51, 3394-3404 (2018).
  5. M. A. Mahmoud, K. Miyatake, submitted.

Molecular Design Strategy of Polyaromatic Ionomers for AEMFCs

Yu Seung Kim1, Sandip Maurya1, Ivana Matanovic2, Cy Fujimoto3 and Chulsung Bae4

1Los Alamos National Laboratory
Materials Physics and Application Division, Los Alamos, New Mexico, USA
yskim@lanl.gov

2The University of New Mexico, Department of Chemical and Biological Engineering, Albuquerque, New Mexico, USA

3Sandia National Laboratories, Materials Science and Engineering Center, Albuquerque, New Mexico, USA

4Rensselaer Polytechnic Institute, Department of Chemistry and Chemical Biology, Tory, New York, USA

Anion exchange ionomers play a significant role in alkaline anion exchange membrane fuel cells (AEMFCs). A recent report has demonstrated 2600 mW/cm2 peak power density of an AEMFC employing an ETFE-based ionomer and commercially available catalysts [1], which emphasizes the importance of ionomers in AEMFC performance. Quaternized polyaromatic ionomers are another promising candidates as these materials possess not only good hydroxide conductivity and mechanical properties but also excellent alkaline stability and processability. However, reported AMFC performance employing polyaromatic ionomers is relatively poor. Last year, we presented the possible causes for the poor AMFC performance including the undesirable phenyl group adsorption [2] and cation-hydroxide-water co-adsorption [3] on hydrogen oxidation reaction catalysts. This year, we will report several molecular design strategy to minimize the undesirable adsorptions using several aryl-ether-free polyaromatic ionomers to demonstrate the progressive improvement of the AMFC performance up to 1,500 mW/cm2 peak power density. In addition, some questions related with AMFC MEA employing polyaromatic ionomers will be discussed:

  • Why Pt-Ru catalyzed AMFC performs better than Pt catalyzed AMFCs?
  • Why high anode flow rate improves much of AMFC performance?
  • What is cost effectiveness using polyaromatic ionomer for low-PGM, non-PGM, and non-Pt anode catalysts?
  • Is electrode flooding significant issue with polyaromatic ionomer-bonded electrodes?

 

References

[1] Wang, L., Ponce Gonzales, J., Bance-Soualhi, R., Whelligan, D., Varcoe, J. R. Abstract No. IO4-1748, 233rd ECS Meeting, Seattle, WA, May 13-17, 2018.

[2] Matanovic, I., Chung, H. T., Kim, Y. S. J. Phys. Chem. Lett. 8 (19), 4918-4924 (2017).

[3] Chung, H. T., Martinez, U., Matanovic, I., Kim, Y. S. J. Phys. Chem. Lett. 7 (22), 4464-4469 (2016).

15:15 | Poster Presentation with Coffee and Snacks

15:45 | Session 7

Robust Hydroxide Ion Conducting Aromatic Polymer Electrolyte Membranes

Chulsung Bae

Department of Chemistry & Chemical Biology, Rensselaer Polytechnic Institute
110 8th Street, Troy, New York, USA
baec@rpi.edu

 

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.

References

(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.

Impact of carbonation processes in anion exchange membrane fuel cells

Ulrike Krewer1, Christine Weinzierl1, Noga Ziv2, Dario Dekel2

1TU Braunschweig, Institute of Energy and Process Systems Engineering
Franz-Liszt-Str. 35, 38114 Braunschweig
u.krewer@tu-braunschweig.de

2The Wolfson Department of Chemical Engineering and the Nancy & Stephan Grand Technion Energy Program (GTEP), Technion, Israel Institute of Technology, Haifa 3200003, Israel

 

Alkaline anion exchange membrane fuel cell (AEMFC) is a promising technology to replace precious metals used today as fuel cell catalysts. However, AEMFC does not yet demonstrate high performance when running on ambient air where they are exposed to CO2. The resulting carbonation reaction reduces membrane conductivity.

This contribution analyses and quantifies the effect of CO2 from ambient air on the concentration profiles in the membrane and the anode and, thus, assesses the CO2 impact on fuel cell performance.[1]. The physico-chemical model contains chemical and electrochemical reactions, liquid-gas phase equilibria as well as the transport processes in the cell. Results imply that a significant part of fed CO2 is absorbed in the cathode and is transported as carbonate ions to the anode. Concentration profiles in the membrane reveal an enrichment zone of CO2 in the membrane close to the anode, negligible HCO3and a wide distribution of CO32- across the membrane. The carbonate distribution affects overall anion exchange membrane conductivity. For practical relevant current densities of i > 500 mA cm-2 and typical excess ratios of 1.5 for the hydrogen feed, less than 10% of the anions in the membrane are CO32-. We show that while increasing cell temperature has an ambiguous effect on the carbonation process and on the total effect of CO2 on the cell, current density has a significant effect. The impact of CO2 on AEMFC performance can be significantly

decreased when operating the cell at high current densities above 1000 mA cm-2 .

Fig.: Distribution of ions in the AEM during operation with air: lH2= 1.1 (- -) , vs1.5(-), 500 mA cm-2 [1]

[1] U. Krewer, C. Weinzierl, N. Ziv, D. Dekel, Electrochimica Acta 263 (2018) 433e446

16:45 | Closing Words

17:40 | Sightseeing

Partners

Organising Committee

Dr. Alexander Dyck – DLR Institute of Networked Energy Systems (Germany)
Prof. Dirk Henkensmeier – Korea Institute of Science and Technology (KIST, South Korea)
Prof. Artur Michalak – Jagiellonian University in Krakow (Poland)

Registration

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 DLR Institute of Networked Energy Systems by June 1st 2018.

Due to the limited number of participants, registrations are considered in order of receipt.

DLR Institute of Networked Energy Systems
Carl-von-Ossietzky-Str. 15 | 26129 Oldenburg | Germany
Phone: +49 441 99906-362
Fax: +49 441 99906-109
Email: emea-ve@dlr.de

Venue

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.

EMEA2017_Venue_1
EMEA2017_Venue_2
EMEA2017_Venue_3

Accommodation

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“.

If you are interested in booking a room in the conference hotel for your overnight stay in Bad Zwischenahn, you can do so by writing an email directly to the hotel (rezeption@hausammeer.de). Rooms are 98.00 € per night. Please refer to the workshop when booking.

Hansens Haus am Meer Hotel
Auf dem Hohen Ufer 25
26160 Bad Zwischenahn, Germany
Phone: +49 4403 940-0
Email: rezeption@hausammeer.de
www.hausammeer.de

Travel

By Plane:
The nearest international airport is Bremen, which is 60 km from Bad Zwischenahn.

By Train:
Bad Zwischenahn has a train station that is served by trains from the rail transport providers “Deutsche Bahn” (www.bahn.de) and “Regio-S-Bahn” (www.regiosbahn.de).

The “Hansens Haus am Meer” hotel offers a free shuttle service from the train station to the hotel on request.

By Car:
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.

Information

The conference fee of €380 includes the lab tour, lunch and coffee breaks on both days as well as the Get-together on Tuesday evening and the conference dinner on Wednesday evening and the VAT. Also covered is the bus tour to the DLR Institute of Networked Energy Systems.

DLR Institute of Networked Energy Systems may charge an administration fee of EUR 70.00 for any change or cancellation of registration. Cancellation must be received by DLR Institute of Networked Energy Systems 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 DLR Institute of Networked Energy Systems, registration fees already paid will be refunded.

If you have any further questions, please do not hesitate to contact us. Workshop contact: Jocelyne Hansen –phone: +49 441 99906-326 – e-mail: emea-ve@dlr.de