Publikationsliste Matthias Breitwieser

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Originalarbeiten in wissenschaftlichen Fachzeitschriften

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2023

• K. Yildirim, H. Fadlullah, C. Schwarz, F. Lombeck, C. Klose, S. Vierrath, M. Breitwieser
  30μm Thin Anode Gas Diffusion Layers for OptimizedPEM Fuel Cell Operation at 120 °C and Low Relative Humidity
  2023 Adv. Energy Sustainability Res, Seite: 2300179
• H. Nguyen, J. Stiegeler, H. Liepold, C. Schwarz, S. Vierrath, M. Breitwieser
  A Comparative Study of Conditioning Methods for Hydrocarbon-Based Proton-Exchange Membrane Fuel Cells for Improved Performance
  2023 Energy Technol., Seite: 2300202
• P. A. Heizmann, H. Nguyen, M. von Holst, A. Fischbach, M. Kostelec, F. J. Gonzalez Lopez, M. Bele, L. Pavko, T. Đukić, M. Šala, F. Ruiz-Zepeda, C. Klose, M. Gatalo, N. Hodnik, S. Vierrath, M. Breitwieser
  Alternative and facile production pathway towards obtaining high surface area PtCo/C intermetallic catalysts for improved PEM fuel cell performance
  2023 RSC Adv, Band: 13, Seiten: 4601 - 4611
• S. Koch, L. Metzler, S. Kilian, P. A. Heizmann, F. Lombeck, M. Breitwieser, S. Vierrath
  Toward scalable production: catalyst‐coated membranes (CCMs) for anion‐exchange membrane water electrolysis via direct bar coating
  2023 Advanced sustainable systems, Band: 7, Seite: 2200332

2022

• E. Balogun, P. Mardle, H. Nguyen, M. Breitwieser, S. Holdcroft
  Catalyst layers for fluorine‐free hydrocarbon PEMFCs
  2022 Electrochimica Acta, Band: 401, Seite: 139479
• H. Nguyen, C. Klose, L. Metzler, S. Vierrath, M. Breitwieser
  Fully Hydrocarbon Membrane Electrode Assemblies for Proton Exchange Membrane Fuel Cells and Electrolyzers: An Engineering Perspective
  2022 Adv. Energy Mater., Band: 2022, Seite: 2103559
• J. Disch, L. Bohn, S. Koch, M. Schulz, Y. Han, A. Tengattini, L. Helfen, M. Breitwieser, S. Vierrath
  High-resolution neutron imaging of salt precipitation and water transport in zero-gap CO2 electrolysis
  2022 nature communications, Band: 13, Seite: 6099
• H. Nguyen, D. Sultanova, P. A. Heizmann, S. Vierrath, M. Breitwieser
  Improving the efficiency of fully hydrocarbon-based proton-exchange membrane fuel cells by ionomer content gradients in cathode catalyst layers
  2022 Materials Advances, Band: 23
• L. Bohn, M. von Holst, E. Cruz Ortiz, M. Breitwieser, S. Vierrath, C. Klose
  Methods— A Simple Method to Measure In-Plane Electrical Resistance of PEM Fuel Cell and Electrolyzer Catalyst Layers
  2022 J.Electrochem. Soc., Band: 169, Nummer: 5, Seite: 054518
• S. Koch, L. Metzler, S. K. Kilian, P. A. Heizmann, F. Lombeck, M. Breitwieser, S. Vierrath
  Toward Scalable Production: Catalyst-Coated Membranes (CCMs) for Anion-Exchange Membrane Water Electrolysis via Direct Bar Coating
  2022 Adv. Sustainable Syst., Seite: 2200332
• S. Koch, J. Disch, S. K. Kilian, Y. Han, L. Metzler, A. Tengattini, L. Helfen, M. Schulz, M. Breitwieser, S. Vierrath
  Water management in anion-exchange membrane water electrolyzers under dry cathode operation
  2022 RSC Adv, Band: 12, Seiten: 20778 - 20784

2021

• H. Nguyen, F. Lombeck, C. Schwarz, P. A. Heizmann, M. Adamski, H-F. Lee, B. Britton, S. Holdcroft, S. Vierrath, M. Breitwieser
  Hydrocarbon-based Pemion™ proton exchange membrane fuel cells with state-of-the-art performance
  2021 Sustainable Energy and Fuels, Band: 5, Seiten: 3687 - 3699
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  Kurzfassung

  Non-fluorinated hydrocarbon ionomers feature distinct technical, cost, and environmental advantages over incumbent perfluorinated sulfonic acid (PFSA)-based ionomers: they offer improved thermo-mechanical properties at temperatures beyond 90 °C, likelihood of lower material cost, lower gas cross-over, and facile recycling of platinum group metals. In addition, fluorine-free hydrocarbon ionomers are less hazardous to the environment owing to the lack of (per)fluorinated precursors. Yet, the performance of hydrogen fuel cells with hydrocarbon-based ionomers and membranes has been historically largely inferior to the PFSA-based state of the art. In this study, we present wholly hydrocarbon fuel cells exceeding previous literature landmarks by a factor of nearly two, with peak power densities of 2.1 W cm−2 under H2/O2 (atmospheric pressure and 95% relative humidity), and 1.1 W cm−2 under H2/air (250 kPaabs and 50% relative humidity). This improvement was achieved by the use of Pemion™ – a sulfo-phenylated polyphenylene-based cation exchange material – as ionomer in the catalyst layer and as proton exchange membrane with a low thickness of 7 μm, and an optimization of cathode catalyst layer based on PtCo/C. Based on an in-depth study of electrochemical performance under various conditions vs. a state-of-the-art PFSA reference cell, the performances of Pemion™-based cells were found to be more sensitive to changes in relative humidity of inlet gases, but the detrimental influence of high temperatures on performance was significantly reduced. At an operation temperature of 110 °C, 250 kPaabs, and 50% relative humidity, the peak power density (0.96 W cm−2) was 8% higher than the short-side chain PFSA-based reference cell (0.89 W cm−2), highlighting the potential of Pemion™ for next-generation fuel cells for heavy-duty or aeronautic applications.
• B. Shanahan, B. Britton, A. Belletti, S. Vierrath, M. Breitwieser
  Performance and stability comparison of Aemion™ and Aemion+™ membranes for vanadium redox flow batteries
  2021 RSC Advances, Band: 11, Nummer: 22, Seiten: 13077 - 13084
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  Kurzfassung

  Anion exchange membranes (AEMs) have shown a significant rise in performance and durability within recent years for applications such as electrolysis and fuel cells. However, in vanadium redox-flow batteries, their use is of particular interest to lower costs and self-discharge rates compared to conventional perfluorinated sulfonic acid-based ionomers such as Nafion. In this work we evaluate the properties of two commercial AEMs, Aemion™ and Aemion+™, based on ex situ characterizations, an accelerated stress test degradation study (>1000 hours storage in highly oxidizing VO2+ electrolyte at 35 °C) and electrochemical battery cycle tests. All membranes feature low ionic resistances of below 320 mΩ cm2, enabling battery cycling at 100 mA cm−2. Aemion shows considerable VO2+ formation within a VO2+ stress test, whereas Aemion+ remains almost unaffected in the 1058 h stress test. Evaluating self-discharge data, cycling performance and durability data, Aemion+™ (50 μm thickness) features the best properties for vanadium redox-flow battery operation.
• B. Shanahan, K. Seteiz, P. A. Heizmann, S. Koch, J. Büttner, S. Ouardi, S. Vierrath, A. Fischer, M. Breitwieser
  Rapid wet-chemical oxidative activation of graphite felt electrodes for vanadium redox flow batteries
  2021 RSC Advances, Band: 11, Nummer: 51, Seiten: 32095 - 32105
• S. Koch, P. A. Heizmann, S. K. Kilian, B. Britton, S. Holdcroft, M. Breitwieser, S. Vierrath
  The effect of ionomer content in catalyst layers in anion-exchange membrane water electrolyzers prepared with reinforced membranes (Aemion+™)
  2021 J. Mater. Chem. A, Band: 9, Seiten: 15744 - 15754

2020

• C. Klose, T. Saatkamp, A. Münchinger, L. Bohn, G. Titvinidze, M. Breitwieser, K.-D. Kreuer, S. Vierrath
  All-Hydrocarbon MEA for PEM Water Electrolysis Combining Low Hydrogen Crossover and High Efficiency
  2020 Adv Energy Mater, Seite: 1903995
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  Kurzfassung

  Hydrocarbon ionomers bear the potential to significantly lower the material cost and increase the efficiency of proton-exchange membrane water electrolyzers (PEMWE). However, no fully hydrocarbon membrane electrode assembly (MEA) with a performance comparable to Nafion-MEAs has been reported. PEMWE-MEAs are presented comprising sPPS as membrane and electrode binder reaching 3.5 A cm−2 at 1.8 V and thus clearly outperforming state-of-the-art Nafion-MEAs (N115 as membrane, 1.5 A cm−2 at 1.8 V) due to a significantly lower high frequency resistance (57 ± 4 mΩ cm² vs 161 ± 7 mΩ cm²). Additionally, pure sPPS-membranes show a three times lower gas crossover (<0.3 mA cm−2) than Nafion N115-membranes (>1.1 mA cm−2) in a fully humidified surrogate test. Furthermore, more than 80 h of continuous operation is shown for sPPS-MEAs in a preliminary durability test (constant current hold at 1 A cm−2 at 80 °C). These results rely on the unique transport properties of sulfonated poly(phenylene sulfone) (sPPS) that combines high proton conductivity with low gas crossover.
• Z. Shu, M. Fechtig, F. Lombeck, M. Breitwieser, Roland Zengerle, Peter Koltay
  Direct Drop-on-Demand Printing of Molten Solder Bumps on ENIG Finishing at Ambient Conditions through StarJet Technology
  2020 IEEE Access, Band: 8, Seiten: 210225 - 210233
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  Kurzfassung

  In this paper, we report on a detailed experimental study carried out with the StarJet technology to investigate the mechanical adhesion properties of directly printed solder bumps on electroless nickel immersion gold (ENIG) plated PCB boards. The aim of this study is to determine the maximum bond strength achievable by this method and to find suitable printing parameters that allow for the production of reliable and consistent solder bumps by non-contact printing of molten solder (type SAC305). Molten solder droplets of about 250 μm diameter were printed at melt temperatures between 250 and 400 °C onto ENIG surfaces kept at temperatures in the range of 100 to 200 °C. Using shear force tests, the adhesion of the printed bumps was investigated as a function of the main process parameters: 1. printhead temperature, 2. substrate temperature, and 3. substrate preheating time. The formation of an intermetallic compound (IMC) between the solder and the ENIG was confirmed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) measurements. As a result of the comprehensive experimental parameter study, suitable printing parameters for establishing bond strengths corresponding to maximum shear force values of 3000 to 4000 mN could be found, i.e. high printhead temperature of 400 °C, short preheating and time of < 2 min, and substrate heating at 180 °C The use of flux was found to slightly improve the bond strength and to improve the consistency of the printing results for extended operation times. The achieved high bond strength and the reasonable reproducibility of the printing results qualify the StarJet technology for further investigations regarding applications in the field of direct soldering of microelectronic chips and devices to PCB boards as well as other micro-assembly tasks in the future.
• F. Hegge, F. Lombeck, E. Cruz Ortiz, L. Bohn, M. von Holst, M. Kroschel, J. Hübner, M. Breitwieser, P. Strasser, S. Vierrath
  Efficient and Stable Low Iridium Loaded Anodes for PEM Water Electrolysis Made Possible by Nanofiber Interlayers
  2020 ACS Appl. Energy Mater, Band: 3, Nummer: 9, Seiten: 8276 - 8284
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  Kurzfassung

  Significant reduction of the precious metal catalyst loading is one of the key challenges for the commercialization of proton-exchange membrane water electrolyzers. In this work we combine IrOx nanofibers with a conventional nanoparticle-based IrOx anode catalyst layer. With this hybrid design we can reduce the iridium loading by more than 80% while maintaining performance. In spite of an ultralow overall catalyst loading of 0.2 mgIr/cm2, a cell with a hybrid layer shows similar performance compared to a state-of-the-art cell with a catalyst loading of 1.2 mgIr/cm2 and clearly outperforms identically loaded reference cells with pure IrOx nanoparticle and pure nanofiber anodes. The improved performance is attributed to a combination of good electric contact and high porosity of the IrOx nanofibers with high surface area of the IrOx nanoparticles. Besides the improved performance, the hybrid layer also shows better stability in a potential cycling and a 150 h constant current test compared to an identically loaded nanoparticle reference.
• E.C. Ortiz, F. Hegge, M. Breitwieser, S. Vierrath
  Improving the performance of proton exchange membrane water electrolyzers with low Ir-loaded anodes by adding PEDOT: PSS as electrically conductive binder
  2020 Rsc Adv, Band: 10, Nummer: 62, Seiten: 37329 - 37927
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  Kurzfassung

  Reducing the iridium catalyst loading in the anode of polymer electrolyte membrane electrolyzers is a major goal to bring down the cost. However, anodes with low Ir-loading can suffer from poor electrical connectivity and hence lower the efficiency of the electrolyzer. In this work, we replace parts of the Nafion binder in the anode with an electrically conductive polymer (poly-3,4-ethylenedioxythiophene and polystyrene sulfonate acid complex, PEDOT:PSS) to counter this effect. At the optimal 50 : 50 blend we achieve a 120 mV lower overpotential (2.02 V) at 3 A cm−2 compared to a pure Nafion reference (2.14 V). This corresponds to a 6% better efficiency. Ex situ resistivity measurements and high frequency resistance measurements indicate that the major cause for this improvement lies in the reduced electrical in-plane resistance due to the electrical conductivity of PEDOT:PSS.
• P. Veh, B. Britton, S. Holdcroft, R. Zengerle, S. Vierrath, M. Breitwieser
  Improving the water management in anion-exchange membrane fuel cells via ultra-thin, directly deposited solid polymer electrolyte
  2020 Rsc Adv, Band: 10, Seiten: 8645 - 8652
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  Kurzfassung

  Thin ionomer membranes are considered key to achieve high performances in anion exchange membrane fuel cells. However, the handling of unsupported anion exchange membranes with thicknesses below 15 μm is challenging. Typical pre-treatments of KOH-soaking, DI-water rinsing and/or wet assembly with sub-15 μm thin films are particularly problematic. In this work, we report configurations of membrane electrode assemblies with solid polymer electrolyte thicknesses equivalent to 3, 5 and 10 μm, made possible by direct coating of the ionomer onto gas diffusion electrodes (direct membrane deposition). The anion-conducting solid polymer electrolyte employed is hexamethyl-p-terphenyl poly(benzimidazolium) (HMT-PMBI), which is known for its high mechanical stability and low rate of gas crossover. By fabricating membrane-electrode-assemblies with PtRu/C anodes and Pt/C cathodes with a low precious metal loading of <0.3 mg cm−2, reproducible performances beyond 1 W cm−2 in H2/O2 atmosphere are achieved. The thin membranes enable excellent performance robustness towards changes in relative humidity, as well as low ionic resistances (<40 mOhm cm2).
• M. Drews, S. Tepner, P. Haberzettl, H. Gentischer, W. Beichel, M. Breitwieser, S. Vierrath, D. Biro
  Towards 3D-lithium ion microbatteries based on silicon/graphite blend anodes using a dispenser printing technique
  2020 RSC Adv., Band: 10, Seiten: 22440 - 22448
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  Kurzfassung

  In this work we present for the first time high capacity silicon/carbon–graphite blend slurries designed for application in 3D-printed lithium ion microbatteries (3D-MLIBs). The correlation between electrochemical and rheological properties of the corresponding slurries was systematically investigated with the prospect of production by an automated dispensing process. A variation of the binder content (carboxymethyl cellulose/styrene–butadiene rubber, CMC/SBR) between 6 wt%, 12 wt%, 18 wt% and 24 wt% in the anode slurry proved to be crucial for the printing process. Regarding the rheological properties increasing binder content leads to increased viscosity and yield stress values promising printed structures with high aspect ratios. Consequently, interdigital 3D-printed micro anode structures with increasing aspect ratios were printed with increasing binder content. For printed 6-layer structures aspect ratios of 6.5 were achieved with anode slurries containing 24 wt% binder. Electrochemical results from planar coin cell measurements showed that anodes containing 12 wt% CMC/SBR binder content exhibited stable cycling at the highest charge capacities of 484 mA h g−1 at a current rate of C/4. Furthermore, at 4C the cells showed high capacity retention of 89% compared to cycling at C/4. Based on this study and the given material formulation we recommend 18 wt% CMC/SBR as the best trade-off between electrochemical and rheological properties for future work with fully 3D-printed MLIBs.
• C. Klose, T. Saatkamp, A. Münchinger, L. Bohn, G. Titvinidze, M. Breitwieser, K.-D. Kreuer, S. Vierrath
  Water Electrolyzers: All‐Hydrocarbon MEA for PEM Water Electrolysis Combining Low Hydrogen Crossover and High Efficiency
  2020 Adv Energy Mater
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  Kurzfassung

  Hydrocarbon ionomers bear the potential to significantly lower the material cost and increase the efficiency of proton‐exchange membrane water electrolyzers (PEMWE). However, no fully hydrocarbon membrane electrode assembly (MEA) with a performance comparable to Nafion‐MEAs has been reported. PEMWE‐MEAs are presented comprising sPPS as membrane and electrode binder reaching 3.5 A cm−2 at 1.8 V and thus clearly outperforming state‐of‐the‐art Nafion‐MEAs (N115 as membrane, 1.5 A cm−2 at 1.8 V) due to a significantly lower high frequency resistance (57 ± 4 mΩ cm² vs 161 ± 7 mΩ cm²). Additionally, pure sPPS‐membranes show a three times lower gas crossover (<0.3 mA cm−2) than Nafion N115‐membranes (>1.1 mA cm−2) in a fully humidified surrogate test. Furthermore, more than 80 h of continuous operation is shown for sPPS‐MEAs in a preliminary durability test (constant current hold at 1 A cm−2 at 80 °C). These results rely on the unique transport properties of sulfonated poly(phenylene sulfone) (sPPS) that combines high proton conductivity with low gas crossover.

2019

• B. Shanahan, T. Böhm, B. Britton, S. Holdcroft, R. Zengerle, S. Vierrath, S. Thiele, M. Breitwieser
  30 μm thin hexamethyl-p-terphenyl poly(benzimidazolium) anion exchange membrane for vanadium redox-flow batteries
  2019 Electrochem Commun, Band: 102, Seiten: 37 - 40
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  Kurzfassung

  We present the first results of an anion exchange ionomer membrane, hexamethyl-p-terphenyl poly(benzimidazolium) (HMT-PMBI), in a vanadium redox flow battery. Anion exchange membranes exhibit superior vanadium crossover suppression compared to proton exchange membranes due to the Gibbs–Donnan effect. HMT-PMBI was benchmarked against a similarly thin Nafion XL membrane which allowed us to compare differences based solely on chemical properties of the ionomer materials. We report cycling data of 45 cycles at a current density of 150 mA/cm2 with excellent coulombic efficiency of >99.4%, energy efficiency of 80.6–74.2% and a low ohmic resistance of 0.219–0.255 Ω cm2. In addition, a three times lower self-discharge rate is obtained for the HMT-PMBI membrane compared to Nafion XL. HMT-PMBI is therefore a potential alternative for PFSA based ionomers in VRFB applications.
• F. Hegge, J. Sharman, R. Moroni, S. Thiele, R. Zengerle, M. Breitwieser, S. Vierrath
  Impact of Carbon Support Corrosion on Performance Losses in Polymer Electrolyte Membrane Fuel Cells
  2019 J Electrochem Soc, Band: 166, Seiten: F956 - F962
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  Kurzfassung

  Corrosion of the carbon support leads to a severe decay in the performance of PEM fuel cells, mainly due to an increase in the oxygen transport resistance. To investigate the effect of degradation on oxygen transport, we cycled MEAs between 1−1.5 V and analyzed the electrode structure with FIB-SEM tomography at various ageing states. The tomography results show that the electrode structure changes over 1000 cycles in terms of thickness (7.8 to 6.5 μm), porosity (44 to 38%) and diffusivity (9 to 8 105 m2s−1). Limiting current measurements in the wet (hydrogen/air) and dry state (hydrogen pumping) allowed the pressure dependent and pressure independent mass transport resistances to be distinguished and to quantify the impact of product water. The pressure independent resistance increased from 24 to 41 sm−1. Considering the marginal contribution of the catalyst pore space resistance (3 to 4 sm−1) it is concluded that the largest portion of the increase (50%) is caused by an increased local mass transport resistance. This is due to a decrease of the electrode roughness factor (282 to 169). The limiting current under wet conditions shows that another 44% could stem from a change in the wetting behavior, while 6% remains unexplained.
• M. Solihul Mu’min, T. Böhm, R. Moroni, R. Zengerle, S. Thiele, S. Vierrath, M. Breitwieser
  Local hydration in ionomer composite membranes determined with confocal Raman microscopy
  2019 Journal of Membrane Science, Band: 585, Seiten: 126 - 135
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  Kurzfassung

  Water management in electrochemical energy applications like fuel cells has a crucial impact on performance, in particular on the ionic conduction of ionomer membranes. To strengthen the understanding of water management in such devices, we report a novel method for non-destructive measurements of the hydration of composite membranes based on confocal Raman microscopy. Composite membranes were produced by spray-coating of Nafion into a mesh of electrospun poly(vinylidene fluoride-co-hexafluoropropylene)/polyvinylpyrrolidone (PVDF-HFP/PVP) blend nanofibers. Hydration levels of several pure nanofiber meshes and nanofiber/Nafion composites were evaluated by linear least squares fitting of reference Raman spectra to hyperspectral images. We found that spectral contribution of water to nanofiber spectra depends on the PVDF-HFP/PVP ratio and is independent from fiber diameter. Further, we were able to reliably determine nanofiber polymer composition of single fibers based on Raman spectroscopy. Raman imaging of composite membranes was performed at ambient air and fully hydrated conditions to study the local hydration in PVDF-HFP/PVP/Nafion composites as well as in a Nafion XL membrane. 2D through-plane mappings revealed that the nanofiber hydration positively correlated with PVP content. In the Nafion XL membrane, the polytetrafluoroethylene-based reinforcement was verified as a hydrophobic layer sandwiched between Nafion ionomer, which showed a more than 10% reduced hydration compared to the outer Nafion layers. These results motivate the use of confocal Raman microscopy as a novel method to investigate the local water distribution in ionomer composite membranes that are widely used in electrochemical energy conversion.
• T. Boehm, R. Moroni, M. Breitwieser, S. Thiele, S. Vierrath
  Spatially Resolved Quantification of Ionomer Degradation in Fuel Cells by Confocal Raman Microscopy
  2019 J Electrochem Soc, Band: 166, Nummer: 7, Seiten: F3044 - F3051
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  Kurzfassung

  Ionomer membranes are crucial components of many electrochemical devices. In this work, confocal Raman microscopy is employed to characterize Nafion ionomers quantitatively in pristine status and after usage as a proton exchange membrane in a fuel cell. Confocal Raman microscopy allows non-destructive thickness and equivalent weight measurements of Nafion with a 95% confidence interval of ±13 g mol−1 at an equivalent weight of 1000 g mol−1, which is significantly more accurate than previously reported methods. Characterization can be performed at a spatial resolution better than 2 μm, providing insights into local membrane degradation after fuel cell operation. Membrane thinning to less than 40% of the initial thickness of Nafion NR-211 occurs after a 100 h open circuit voltage hold, accompanied by an anisotropic increase of the equivalent weight from 1035 g mol−1 to an average of 1200 g mol−1. Most pronounced increases are found close to the anode. Further, the characterization of a Nafion XL membrane shows that its microporous reinforcement is represented as increased equivalent weight with local heterogeneities within the membrane. These results show that confocal Raman microscopy is a valuable tool to investigate ionomers that are used as ion exchange membranes in electrochemical devices.

2018

• B. Gerdes, M. Breitwieser, T. Kaltenbach, M. Jehle, J. Wilde, R. Zengerle, P. Koltay, L. Riegger
  Analysis of the metallic structure of microspheres produced by printing of aluminum alloys from the liquid melt
  2018 Mater Res Express, Band: 6, Seite: 036514
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  Kurzfassung

  This work presents an analysis of the metallic structure of microspheres produced by drop-on-demand printing of the aluminum alloy AlSi12 directly printed from the liquid melt via StarJet technology. AlSi alloys are commonly used in casting processes, but microdroplets from these materials could potentially be used for additive manufacturing of metal and composite parts. Recently, several printing technologies were presented that enable the drop-on-demand printing of Al-alloy microdroplets. However, the material distribution and metallic structure inside of printed droplets is expected to be significantly different from the bulk material properties, and hardly any data on the microscopic structure of small droplets that have undergone rapid solidification has been published so far. Therefore, a microscopic in-depth study of microdroplets printed directly from the metal melt has been carried out: By the means of energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and optical microscopy the material properties as well as the droplet morphology are investigated for the first time. The analysis demonstrates that the Al alloy droplets printed via StarJet technology exhibit almost no oxidation during the printing process and can therefore potentially be used for additive manufacturing of metal parts. Moreover, the metallurgical structure inside the droplets is analyzed. It exhibits significant difference to the bulk material in terms of the average secondary dendrite arm spacing.

2017

• M. Breitwieser, T. Bayer, A. Büchler, R. Zengerle, S. M. Lyth, S. Thiele
  A fully spray-coated fuel cell membrane electrode assembly using Aquivion ionomer with a graphene oxide/cerium oxide interlayer
  2017 J Power Sources, Band: 351, Seiten: 145 - 150
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  Kurzfassung

  A novel multilayer membrane electrode assembly (MEA) for polymer electrolyte membrane fuel cells (PEMFCs) is fabricated in this work, within a single spray-coating device. For the first time, direct membrane deposition is used to fabricate a PEMFC by spraying the short-side-chain ionomer Aquivion directly onto the gas diffusion electrodes. The fully sprayed MEA, with an Aquivion membrane 10 mm in thickness, achieved a high power density of 1.6 W/cm2 for H2/air operation at 300 kPaabs. This is one of the highest reported values for thin composite membranes operated in H2/air atmosphere. By the means of confocal laser scanning microscopy, individual carbon fibers from the gas diffusion layer are identified to penetrate through the micro porous layer (MPL), likely causing a low electrical cell resistance in the range of 150 U cm2 through the thin sprayed membranes. By spraying a 200 nm graphene oxide/cerium oxide (GO/CeO2) interlayer between two layers of Aquivion ionomer, the impact of the electrical short is eliminated and the hydrogen crossover current density is reduced to about 1 mA/cm2. The peak power density of the interlayer-containing MEA drops only by 10% compared to a pure Aquivion membrane of similar thickness.
• M. Breitwieser, C. Klose, A. Hartmann, A. Büchler, M. Klingele, S. Vierrath, R. Zengerle, S. Thiele
  Cerium Oxide Decorated Polymer Nanofibers as Effective Membrane Reinforcement for Durable, High-Performance Fuel Cells
  2017 Adv Energy Mater, Seite: 1602100
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  Kurzfassung

  High-power, durable composite fuel cell membranes are fabricated here by direct membrane deposition (DMD). Poly(vinylidene fluoride-co-hexafluo- ropropylene) (PVDF-HFP) nanofibers, decorated with CeO 2 nanoparticles are directly electrospun onto gas diffusion electrodes. The nanofiber mesh is impregnated by inkjet-printed Nafion ionomer dispersion. This results in 12 µm thin multicomponent composite membranes. The nanofibers provide membrane reinforcement, whereas the attached CeO 2 nanoparticles promote improved chemical membrane durability due to their radical scavenging properties. In a 100 h accelerated stress test under hot and dry conditions, the reinforced DMD fuel cell shows a more than three times lower voltage decay rate (0.39 mV h −1 ) compared to a comparably thin Gore membrane (1.36 mV h −1 ). The maximum power density of the DMD fuel cell drops by 9%, compared to 54% measured for the reference. Impedance spectroscopy reveals that ionic and mass transport resistance of the DMD fuel cell are unaffected by the accelerated stress test. This is in contrast to the reference, where a 90% increase of the mass transport resistance is measured. Energy dispersive X-ray spectroscopy reveals that no significant migration of cerium into the catalyst layers occurs during degradation. This proves that the PVDF- HFP backbone provides strong anchoring of CeO 2 in the membrane.
• C. Klose, M. Breitwieser, S. Vierrath, M. Klingele, H. Cho, A. Büchler, J. Kerres, S. Thiele
  Electrospun sulfonated poly(ether ketone) nanofibers as proton conductive reinforcement for durable Nafion composite membranes
  2017 J Power Sources, Band: 361, Seiten: 237 - 242
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  Kurzfassung

  We show that the combination of direct membrane deposition with proton conductive nanofiber reinforcement yields highly durable and high power density fuel cells. Sulfonated poly(ether ketone) (SPEK) was directly electrospun onto gas diffusion electrodes and then filled with Nafion by inkjet-printing resulting in a 12 μm thin membrane. The ionic membrane resistance (30 mΩ*cm2) was well below that of a directly deposited membrane reinforced with chemically inert (PVDF-HFP) nanofibers (47 mΩ*cm2) of comparable thickness. The power density of the fuel cell with SPEK reinforced membrane (2.04 W/cm2) is 30% higher than that of the PVDF-HFP reinforced reference sample (1.57 W/cm2). During humidity cycling and open circuit voltage (OCV) hold, the SPEK reinforced Nafion membrane showed no measurable degradation in terms of H2 crossover current density, thus fulfilling the target of 2 mA/cm2 of the DOE after degradation. The chemical accelerated stress test (100 h OCV hold at 90 °C, 30% RH, H2/air, 50/50 kPa) revealed a degradation rate of about 0.8 mV/h for the fuel cell with SPEK reinforced membrane, compared to 1.0 mV/h for the PVDF-HFP reinforced membrane.
• M. Breitwieser, C. Klose, M. Klingele, A. Hartmann, J. Erben, H. Cho, J. Kerres, R. Zengerle, S. Thiele
  Simple fabrication of 12 μm thin nanocomposite fuel cell membranes by direct electrospinning and printing
  2017 J Power Sources, Band: 337, Seiten: 137 - 144
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  Kurzfassung

  Direct membrane deposition (DMD) was recently introduced as a novel polymer electrolyte membrane fabrication method. Here, this approach is extended to fabricate 12 μm thin nanocomposite fuel cell membranes. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanofibers are directly electrospun onto gas diffusion electrodes. By inkjet-printing Nafion ionomer dispersion into the pore space of PVDF-HFP nanofiber mats, composite membranes of 12 mm thickness were fabricated. At 120 C and 35% relative humidity, stoichiometric 1.5/2.5 H2/air flow and atmospheric pressure, the power density of the DMD fuel cell (0.19Wcm-2), was about 1.7 times higher than that of the reference fuel cell (0.11Wcm-2) with Nafion HP membrane and identical catalyst. A lower ionic resistance and, especially at 120 C, a reduced charge transfer resistance is found compared to the Nafion HP membrane. A 100 h accelerated stress test revealed a voltage decay of below 0.8 mV h-1, which is in the range of literature values for significantly thicker reinforced membranes. Finally, this novel fabrication approach enables new degrees of freedom in the design of complex composite membranes. The presented combination of scalable deposition techniques has the potential to simplify and thus reduce cost of composite membrane fabrication at a larger scale.
• M. Breitwieser, M. Klingele, S. Vierrath, R. Zengerle, S. Thiele
  Tailoring the membrane-electrode interface in PEM fuel cells: A review and perspective on novel engineering approaches
  2017 Adv Energy Mater, Seite: 1701257

2016

• M. Klingele, B. Britton, M. Breitwieser, S. Vierrath, R. Zengerle, S. Holdcroft, S. Thiele
  A Completely Spray-Coated Membrane Electrode Assembly
  2016 Electrochem Commun, Band: 70, Seiten: 65 - 68
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  Kurzfassung

  We present a proton exchange membrane fuel cell (PEMFC) manufacturing route, in which a thin layer of polymer electrolyte solution is spray-coated on top of gas diffusion electrodes (GDEs) to work as a proton exchange membrane. Without the need for a pre-made membrane foil, this allows inexpensive, fast, large-scale fabrication of membrane-electrode assemblies (MEAs), with a spray-coater comprising the sole manufacturing device. In this work, a catalyst layer and a membrane layer are consecutively sprayed onto a fibrous gas diffusion layer with applied microporous layer as substrate. A fuel cell is then assembled by stacking anode and cathode half-cells with the membrane layers facing each other. The resultant fuel cell with a low catalyst loading of 0.1 mg Pt/cm2 on each anode and cathode side is tested with pure H2 and O2 supply at 80 °C cell temperature and 92% relative humidity at atmospheric pressure. The obtained peak power density is 1.29 W/cm2 at a current density of 3.25 A/cm2. By comparison, a lower peak power density of 0.93 W/cm2 at 2.2 A/cm2 is found for a Nafion NR211 catalyst coated membrane (CCM) reference, although equally thick membrane layers (approx. 25 μm), and identical catalyst layers and gas diffusion media were used. The superior performance of the fuel cell with spray-coated membrane can be explained by a decreased low frequency (mass transport) resistance, especially at high current densities, as determined by electrochemical impedance spectroscopy.
• N. Wehkamp, M. Breitwieser, A. Büchler, M. Klingele, R. Zengerle, S. Thiele
  Directly deposited Nafion/TiO2 composite membranes for high power medium temperature fuel cells
  2016 Rsc Adv, Band: 6, Seiten: 24261 - 24266
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  This work presents a simple production method for TiO2 reinforced Nafion® membranes which are stable up to a 120 °C operation temperature. The novel TiO2 reinforced membranes yield a maximum power density of 2.02 W cm−2 at 120 °C; H2/O2; 0.5/0.5 L min−1; 90% RH, 300/300 kPaabs. This is 2.8 times higher than the highest power density for TiO2 reinforced membranes so far published in literature. The described membranes even exceed the maximum power density of a commercial Nafion® HP membrane in an identical measurement setup at 100 °C and 120 °C. Compared to the commercial Nafion® HP membrane the maximum power density was increased by 27% and 9% at 100 °C and 120 °C, respectively. The membrane is manufactured by drop-casting a dispersion of Nafion® and TiO2 nanoparticles onto both the anode and cathode gas diffusion electrodes. Furthermore pure Nafion® membranes manufactured by the same method had higher membrane resistances at temperatures >100 °C than TiO2-reinforced Nafion® membranes.
• S. Vierrath, M. Breitwieser, M. Klingele, B. Britton, S. Holdcroft, R. Zengerle, S. Thiele
  The reasons for the high power density of fuel cells fabricated with directly deposited membranes
  2016 J. of Power Sources, Band: 326, Seiten: 170 - 175
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  Kurzfassung

  In a previous study, we reported that polymer electrolyte fuel cells prepared by direct membrane deposition (DMD) produced power densities in excess of 4 W/cm2. In this study, the underlying origins that give rise to these high power densities are investigated and reported. The membranes of high power, DMD-fabricated fuel cells are relatively thin (12 mm) compared to typical benchmark, commercially available membranes. Electrochemical impedance spectroscopy, at high current densities (2.2 A/cm2) reveals that mass transport resistance was half that of reference, catalyst-coated-membranes (CCM). This is attributed to an improved oxygen supply in the cathode catalyst layer by way of a reduced propensity of flooding, and which is facilitated by an enhancement in the back diffusion of water from cathode to anode through the thin directly deposited membrane. DMD-fabricated membrane-electrode-assemblies possess 50% reduction in ionic resistance (15 mUcm2) compared to conventional CCMs, with contributions of 9 mUcm2 for the membrane resistance and 6 mUcm2 for the contact resistance of the membrane and catalyst layer ionomer. The improved mass transport is responsible for 90% of the increase in power density of the DMD fuel cell, while the reduced ionic resistance accounts for a 10% of the improvement.
• M. Breitwieser, R. Moroni, J. Schock, M. Schulz, B. Schillinger, F. Pfeiffer, R. Zengerle, S. Thiele
  Water management in novel direct membrane deposition fuel cells under low humidification
  2016 Int J Hydrog Energ, Band: 41, Seiten: 11412 - 11417
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  Kurzfassung

  Polymer electrolyte membrane fuel cells (PEMFCs) fabricated by direct membrane deposition (DMD) were shown to work even at dry conditions without significant deterioration of the membrane resistance. Here, in situ neutron radiography is used to investigate the water management in those fuel cells to uncover the phenomena that lead to the robust operation under low humidification. A constant level of humidification within the membrane electrode assembly (MEA) of a DMD fuel cell is observed even under dry anode operation and 15% relative humidity on the cathode side. This proves a pronounced back diffusion of generated water from the cathode side to the anode side through the thin deposited membrane layer. Over the entire range of polarization curves a very high similarity of the water evolution in anode and cathode flow fields is found in spite of different humidification levels. It is shown that the power density of directly deposited membranes in contrast to a 50 mm thick N-112 membrane is only marginally affected by dry operation conditions. Water profiles in through-plane direction of the MEA reveal that the water content in the DMD fuel cell remains steady even at high current densities. This is in contrast to the N-112 reference fuel cell which shows a strong increase in membrane resistance and a reduced MEA water content with raising current densities. Thus this new MEA fabrication technique has a promising perspective, since dry operation conditions are highly requested in order to reduce fuel cell system costs.

2015

• M. Klingele, M. Breitwieser, R. Zengerle, S. Thiele
  Direct Deposition of Proton Exchange Membranes Enabling High Performance Hydrogen Fuel Cells
  2015 J. Mat. Chem. A, Band: 3, Seiten: 11239 - 11245
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  Kurzfassung

  We apply drop-on-demand inkjet printing to fabricate proton exchange membranes for polymer electrolyte fuel cells. This completely substitutes the commonly used membrane foil. A Nafion® dispersion is deposited directly onto the catalyst layers of anode and cathode gas diffusion electrodes, and the two electrodes are pressed together with membrane layers facing each other. Fuel cells constructed utilizing this method reveal a thin overall membrane thickness of 8-25 µm and a good adhesion of membrane and catalyst layers. This results in a membrane ionic resistance of only 12.7 mΩ*cm² without compromising hydrogen crossover, which was determined to be less than 2 mA/cm². We achieve a cell power density exceeding 4 W/cm² with pure oxygen as cathode fuel, which, to our knowledge, is the highest reported power density with a Nafion® membrane hydrogen fuel cell. The membrane shows a stable performance over the entire range of reactant gas humidification from 0 to 100 % relative humidity. Power densities exceeding 1.0 W/cm² are achieved under dry operation with air as cathode fuel. A 576 hour combined mechanical and chemical accelerated stress test reveals no significant degradation of hydrogen crossover, indicating a promising lifetime of the membrane.
• M. Breitwieser, M. Klingele, B. Britton, S. Holdcroft, R. Zengerle, S. Thiele
  Improved Pt-utilization efficiency of low Pt-loading PEM fuel cell electrodes using direct membrane deposition
  2015 Electrochem Commun, Band: 60, Seiten: 168 - 171
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  Kurzfassung

  Direct membrane deposition was used to produce record platinum catalyst utilization efficiency polymer electrolyte membrane fuel cells. The novel membrane fabrication technique was applied to gas diffusion electrodes with low Pt-loadings of 0.102 and 0.029 mg/cm2. Under oxygen atmosphere and 300 kPaabs total pressure, 88 kW/gPt cathodic catalyst utilization efficiency with a symmetrical Pt-loading of 0.029 mg/cm2 on the anode and cathode side was achieved. This is 2.3 times higher than the Pt-utilization efficiency of a reference fuel cell prepared using a commercial Nafion N-211 membrane and identical catalyst layers, emphasizing that the improvement is purely attributable to the novel membrane fabrication technique. This value represents the highest Pt-utilization efficiency reported in literature. The results strongly motivate the application of employing direct membrane deposition techniques to prepare low resistance polymer electrolyte thin films in order to compensate for kinetic losses introduced when using low catalyst loadings.

Vorträge

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2022

• L. Metzler, S. Koch, M. Elshamy, S. Kilian, M. Breitwieser, S. Vierrath
  Fully casted catalyst coated membranes for anion exchange membrane water electrolysis
  2022 Workshop on Ion Exchange Membranes for Energy Applications, Bad Zwischenahn, June 20 – 22, 2022
• M. von Holst, L. Pavko, J. Stiegeler, P. A. Heizmann, A. Salihi, M. Gatalo, N. Hodnik, C. Klose, S. Vierrath, M. Breitwieser
  Reduced graphene oxide as durable carbon support for PtCo catalyst in proton exchange membrane fuel cells
  2022 Symposium Nano-BW 2022 des Kompetenznetzes „Funktionelle Nanostrukturen“, Bad Herrenalb, December, 6-7, 2022

2018

• S. Vierrath, M. Breitwieser, C. Klose, M. Klingele, S. Thiele
  Novel approaches to tailor the PEM|electrode interface for fuel cells with increased power density
  2018 innBW Wissenschaftlertreffen Stuttgart, 21.04.2018
• M. Breitwieser, S. Vierrath
  Neue Kompositmembranen und Mikrocharakterisierung: Die Gruppe „Elektrochemische Energiesysteme“ an IMTEK und Hahn-Schickard
  2018 Brennstoffzellenallianz Duisburg, 26. - 27. Juni 2018

2016

• C. Klose, M. Breitwieser, L. Zielke, S. Vierrath, H. Cho, S. Thiele, J. Kerres, R. Zengerle
  Long-life and high-power PEMFCs by combination of direct electrospinning and inkjet printing,
  2016 Statusworkshop der Baden-Württemberg Stiftung, Bad Herrenalb, 2016
• M. Breitwieser, M. Klingele, B. Britton, S. Vierrath, R. Zengerle, S. Holdcroft, S. Thiele
  Recent Progress in Low- and No- Pt loaded PEMFCs
  2016 Electrocatalysis Workshop, Vancouver, February 2016

Konferenzbeiträge

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2023

• E. Cruz Ortiz, M. Breitwieser, S. Vierrath, M. Bühler
  Effect of compression on the membrane electrode assembly of polymer electrolyte electrolyzers
  2023 EFCF 2023, Low Temperature Fuel Cells, Electrolysers & H2 Processing Forum, Lucerne/Switzerland, July 4-7, 2023
• F. Pescher, M. von Holst, P. Heizmann, S. Vierrath, M. Breitwieser
  Novel Catalysts for Proton Exchange Membrane Fuel Cells via Fluidized Bed Atomic Layer Deposition
  2023 EFCF 2023, Low Temperature Fuel Cells, Electrolysers & H2 Processing Forum, Lucerne/Switzerland, July 4-7, 2023
• F. Pescher, M. von Holst, A. Salihi, J. Stiegeler, P. Heizmann, S. Vierrath, M. Breitwieser
  Platinum Catalysts for Proton Exchange Membrane Fuel Cells via Fluidized Bed Atomic Layer Deposition
  2023 ECS Meeting, Gothenburg / Sweden, 8.-12.10.2023

2022

• C. Schwarz, F. Lombeck, H. Nguyen, F. Khan, D. Sultanova, K. Yildirim, M. Breitwieser
  Development of roll-to-roll feasible, direct coating technique for membrane electrode assemblies
  2022 Fuel Cells, Gordon Research Conference, Smithfield, RI, USA, July 24 - 29, 2022
• E. Cruz Ortiz, M. Breitwieser, S. Vierrath, M. Bühler
  Effect of compression on the membrane electrode assembly of polymer electrolyte electrolyzers
  2022 ICE 2021, 3rd International Conference on Electrolysis 2021, Golden, Colorado USA, June 12-17, 2022
• J. Disch, L. Bohn, S. Koch, M. Schulz, Y. Han, M. Breitwieser, S. Vierrath
  High-resolution neutron imaging of carbonate precipitation and water transport in CO2 electrolysis to CO
  2022 Swiss Electrochemistry Symposium, Aarau, Switzerland, May 11, 2022
• J. Disch, L. Bohn, S. Koch, M. Schulz, Y. Han, M. Breitwieser, S. Vierrath
  High-resolution neutron imaging of carbonate precipitation and water transport in CO2 electrolysis to CO
  2022 Gordons Solar Fuels, Lucca, Italy, May 8-13, 2022
• H. Nguyen, D. Sultanova, F. Lombeck, C. Schwarz, P. A. Heizmann, C. Klose, S. Vierrath, M. Breitwieser
  PEM fuel cells based on novel hydrocarbon ionomers: Approaching state-of-the-art performance
  2022 Fuel Cells, Gordon Research Conference, Smithfield, RI, USA, July 24 - 29, 2022
• M. von Holst, L. Pavko, J. Stiegeler, P. A. Heizmann, A. Salihi, M. Gatalo, N. Hodnik, C. Klose, S. Vierrath, M. Breitwieser
  Reduced graphene oxide as durable carbon support for PtCo catalyst in proton exchange membrane fuel cells
  2022 Fuel Cells, Gordon Research Conference, Smithfield, RI, USA, July 24 - 29, 2022
• S. Koch, S. K. Kilian, J. L. Disch, L. Metzler, P. A. Heizmann, Y. Han, M. Schulz, M. Breitwieser, S. Vierrath
  Water management in anion-exchange membrane water electrolyzers under dry cathode operation
  2022 GPR 2022, Golden, Colorado USA, June 12-17, 2022

2021

• H. Nguyen, F. Lombeck, C. Schwarz, P. A. Heizmann, M. Adamski, H-F. Lee, B. Britton, S. Holdcroft, S. Vierrath, M. Breitwieser
  A fluorine-free hydrocarbon-based proton exchange membrane fuel cell with state-of-the-art performance
  2021 23rd European Fuel Cell Forum (EFCF), Lucerne, Switzerland (Online), 2.-5.07.2021
• C. Schwarz, S. Vierrath, M. Breitwieser
  Elucidating the impact of Pt-ink ageing on fuel cell performance in laboratory scale CCM production
  2021 23rd European Fuel Cell Forum (EFCF), Lucerne, Switzerland (Online), 2.-5.07.2021
• C. Klose, T. Saatkamp, A. Münchinger, L. Bohn, G. Titvinidze, M. Breitwieser, S. Vierrath,
  Fluorine-free membrane electrode assemblies for water electrolysis based on sulfonated polyphenylensulfone
  2021 23rd European Fuel Cell Forum (EFCF), Lucerne, Switzerland (Online), 2.-5.07.2021
• E. Ortiz, F. Lombeck, M. Kroschel, J. Hübner, L. Bohn, M. von Holst, M. Breitwieser, P. Strasser, S. Vierrath
  Highly efficient low-loaded Ir-anodes proton exchange membrane water electrolysis: concepts to reduce in-plane resistance
  2021 23rd European Fuel Cell Forum (EFCF), Lucerne, Switzerland (Online), 2.-5.07.2021
• S. Koch, S. K. Kilian, P. A. Heizmann, M. Breitwieser, S. Vierrath
  Improving anion-exchange-membrane water electrolyzers by adjusting the ionomer content in the catalyst layers
  2021 23rd European Fuel Cell Forum (EFCF), Lucerne, Switzerland (Online), 2.-5.07.2021
• P. A. Heizmann, M. von Holst, H. Nguyen, F. Lombeck, C. Schwarz, C. Klose, M. Breitwieser, S. Vierrath
  Linking morphological properties of Pt/C catalysts to electrochemical performances for improved catalysis in fuel cells
  2021 23rd European Fuel Cell Forum (EFCF), Lucerne, Switzerland (Online), 2.-5.07.2021
• P. A. Heizmann, C. Klose, M. Breitwieser, S. Vierrath
  Quantitative STEM tomography for proton exchange membrane fuel cell apllications
  2021 Symposium Nano-BW, Bad Herrenalb, online, 07.10.2021
• K. Seteiz, B. Shanahan, P. A. Heizmann, S. Koch, J. Büttner, S. Ouardi, S. Vierrath, A. Fischer, M. Breitwieser
  Rapid wet-chemical oxidative activation of graphite felt electrodes for vanadium redox flow batteries
  2021 2nd Electrochemical Cell Concepts Colloquium (Virtual E3C), Oberhausen, Germany (Online), 6.5.2021
• S. Vierrath, E. Cruz Ortiz, F. Hegge, T. Böhm, F. Lombeck, M. Breitwieser
  Tackling durability and efficiency in polymer membrane fuel cells and electrolysis
  2021 MRS Seattle/Washington, USA (online), 10. – 14.04.2021
• P. A. Heizmann, M. von Holst, F. Lombeck, H. Nguyen, C. Klose, M. Breitwieser, S. Vierrath
  Understanding the platinum carbon-support interaction for improved catalysis in hydrogen fuel cells
  2021 9th NRW Nano Conference: Innovations in Materials and Applications, Münster, Germany (Online), 21.-23.04.2021

2020

• F. Lombeck, F. Hegge, M. von Holst, C. Klose, S. Vierrath, M. Breitwieser
  Ceramic Nanofibers: A versatile material class to improve Electrochemical Energy Applications
  2020 71st International Society of Electrochemistry, Belgrad, Serbia (Online), 30.08. – 04.09.2020
• H. Nguyen, P. A. Heizmann, F. Lombeck, A. Belletti, B. Britton, S. Vierrath, M. Breitwieser
  Improving the Performance of All-Hydrocarbon PEM Fuel Cells Based on Pemion™ Ionomer
  2020 71st International Society of Electrochemistry, Belgrad, Serbia (Online), 30.08. – 04.09.2020
• M. Breitwieser, S. Vierrath
  One for all or one for each application? Recent advances in membrane & ionomer development for electrochemical energy converters
  2020 E3C Electrochemical Cell Concepts Colloquium Fraunhofer UMSICHT, 14.05.2020
• E. Cruz Ortiz, F. Hegge, M. Breitwieser, S. Vierrath
  Performance Improvement of PEM Water Electrolyzer Anodes via a Bi-Functional Binder Polymer Blends for Ionic and Electrical Conduction
  2020 71st International Society of Electrochemistry, Belgrad, Serbia (Online), 30.08. – 04.09.2020
• S. Koch, C. Klose, B. Britton, M. Breitwieser, S. Vierrath
  Towards stable catalyst layers for water electrolysis based on anion-exchange membranes
  2020 71st International Society of Electrochemistry, Belgrad, Serbia (Online), 30.08. – 04.09.2020

2019

• B. Shanahan, T. Böhm, B. Britton, S. Holdcroft, S. Vierrath, S. Thiele, M. Breitwieser
  30 μm thin hexamethyl-p-terphenyl poly(benzimidazolium) anion exchange membrane for vanadium redox flow batteries
  2019 The International Flow Battery Forum, Lyon/France, 09 - 11 July 2019
• T. Boehm, M. S. Mu’min, R. Moroni, S. Thiele, S. Vierrath, M. Breitwieser
  Resolving structure and properties in ionomer composite membranes with Confocal Raman Microscopy
  2019 Workshop on Ion Exchange Membranes for Energy Applications, Bad Zwischenahn, 25. -27.06. 2019
• T. Boehm, M. S. Mu’min, R. Moroni, S. Thiele, S. Vierrath, M. Breitwieser
  Resolving structure and properties in ionomer composite membranes with Confocal Raman Microscopy
  2019 FDFC 2019 - 8th International Conference on Fundamentals and Development of Fuel Cells Nantes/France, 12. – 14.02.2019

2018

• B. Shanahan, B. Britton, S. Holdcroft, R. Zengerle, S. Thiele, M. Breitwieser
  30 μm thin, highly conductive PBI-based anion exchange membrane (AEM) for VRFB applications
  2018 IFBF - The International Flow Battery Forum, Lausanne/Schweiz, 10. – 12.07.2018
• C. Klose, L. Bohn, M. Klingele, S. Thiele, R. Zengerle, M. Breitwieser, S. Vierrath
  Dynamic Quantification of Water Generation and Migration in Polymer Electrolyte Membrane Fuel Cells
  2018 69th annual meeting of the International Society of Electrochemistry, Bologna (Italy), 02. - 07.09.2018.
• C. Klose, L. Bohn, M. Klingele, S. Thiele, R. Zengerle, M. Breitwieser, S. Vierrath
  Dynamic Quantification of Water Generation and Migration in Polymer Electrolyte Membrane Fuel Cells
  2018 Gordon’s Research Conference on Fuel Cells, Smithfield (USA), 29.07. - 03.08.2018
• C. Klose, L. Bohn, M. Klingele, M. Breitwieser, S. Vierrath
  How engineering the PEM|CL interface influences the performance of PEMFCs
  2018 69th Annual Meeting of the International Society of Electrochemistry (ISE), Bologna/Italy, 02. – 07.09.2018
• C. Klose, L. Bohn, M. Klingele, M. Breitwieser, S. Vierrath
  Influence of the PEM|CL interface on performance and water management
  2018 Gordon Research Conference, Bryant University, Douglas Pike in Smithfield, RI, US., 29.07. – 03.08.2018
• S. Vierrath, M. Klingele, S. Thiele, R. Zengerle, M. Breitwieser
  Tailoring the membrane│electrode interface: a review and perspective of novel engineering approaches
  2018 69th Annual Meeting of the International Society of Electrochemistry (ISE), Bologna/Italy, 02. – 07.09.2018
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  69th Annual Meeting of the International Society of Electrochemistry (ISE), Bologna/Italy, 02. – 07.09.2018
• M. Mu’min Solihul, T. Böhm, S. Thiele, M. Breitwieser
  Towards more hydrophilic proton exchange membranes: adjusting the wetting properties by electrospinning PVDF-HFP/PVP blends
  2018 ELEN Electrospinning for Energy, Montpellier / Fracne, 13. - 15.06.2018

2017

• S. Vierrath, M. Breitwieser, M. Bühler, C. Klose, R. Zengerle, S. Thiele
  Additive Fertigung für Brennstoffzellen und Elektrolyse
  2017 MST Kongress, München, 23. - 25.10.2017
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  Kurzfassung

  Bei der Wasserstoff-Elektrolyse wird Wasser mit Hilfe von Strom in Wasserstoff umgewandelt, der dann als Energieträger gespeichert werden kann. Bei der Brennstoffzelle wird dieser Prozess umgekehrt und somit Strom erzeugt. Zusammen bilden diese Systeme die Grundlage der zukünftigen Wasserstoffwirtschaft, in der große Energiemengen, z.B. aus erneuerbaren Quellen, flexibel gespeichert und abgerufen werden können. Die Brennstoffzelle ermöglicht zudem eine emissionslose Mobilität ohne Reichweitenbegrenzung oder lange Ladezeiten. Die Membran-Elektroden-Einheit bildet das Herzstück der Brennstoffzelle und der Elektrolysezelle. Darin ist die Membran nur für Wasserstoffionen durchlässig und sorgt so für kontrollierte Reaktionen in den beidseitig aufgebrachten Elektroden. Die Qualität dieser Membran-Elektroden-Einheit entscheidet maßgeblich über die Leistung und Alterungsverhalten in der späteren Anwendung. Klassischerweise werden die Elektroden und die Membran getrennt betrachtet und hergestellt – dabei hat die Grenzschicht einen beachtlichen Einfluss auf das Leistungsverhalten. Wir gehen mit additiver Fertigungstechnik neue Wege in der Herstellung: Statt die Membran in Folienprozessierung und die Elektroden im Sprüh-Abzieh-Verfahren herzustellen, können wir die gesamte Membran-Elektroden-Einheit nacheinander in einem Sprühprozess herstellen (Abb.1) [1]. Neben der Vereinfachung des Prozesses bildet die aufgesprühte Membran eine dreidimensionale Grenzfläche mit den Elektroden, statt der herkömmlichen 2D-Grenzfläche der Membranfolie. Die vergrößerte Grenzschicht und der verbesserte ionische Kontakt sorgen für eine 40% höhere Maximalleistung (Abb. 2a) und besseres Wassermanagement bei großen Strömen [2]. Dank additiver Fertigung ist zudem die gezielte ortsaufgelöste Aufbringung der Materialien möglich. So kann Material eingespart und auch die Membran-Elektroden-Einheit lokal optimiert werden, z.B. durch Anpassung des Katalysator- oder Ionomergehalts an das Reaktionsprofil. Neben der Leistung und dem Herstellungsprozess ist auch das Alterungsverhalten ein wichtiger Aspekt. Durch die Integration von Nanofasern und Nanopartikeln kann die mechanische und chemische Stabilität erheblich gesteigert werden (Abb. 2b) [3]. Dazu werden Nanofasern direkt auf die Elektrode gesponnen und anschließend mit Ionomer besprüht um eine Kompositmembran zu erhalten [4]. Die Nanopartikel können gezielt in eine Schicht, z.B. als Radikalfänger in der Membran, integriert werden.
• M. Breitwieser, S. Vierrath, C. Klose, M. Klingele, R. Zengerle, S. Thiele
  Direct Membrane Deposition (DMD): A novel and versatile fabrication technique for high performance fuel cells
  2017 7th International Conference on ”Fundamentals & Development of Fuel Cells” in Stuttgart, 31. Januar – 2. Februar 2017
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  Kurzfassung

  In the “Direct Membrane Deposition” (DMD) technique the conventional catalyst coated membrane (CCM) is replaced by two ionomer-coated gas diffusion electrodes (GDE). Assembling the ionomer-coated GDEs creates a fuel cell with a very thin membrane (12 μm) and improved interface between membrane and electrodes. Fuel cells fabricated with DMD showed record power densities of 4 W/cm² at 70°C, 300 kPa and with oxygen as fuel. The DMD approach also proved its suitability for medium temperature fuel cells: by incorporating TiO2 nanoparticles into the directly deposited membrane the fuel cell showed stable operation at 120°C with a power density of 2 W/cm² (300 kPa and oxygen at the cathode). Besides the increased power density, DMD bears the potential to simplify the membrane-electrode-assembly (MEA) fabrication process by successively spray-coating catalyst layer and membrane onto a gas diffusion layer. In very recent work, DMD was used to fabricate composite membranes by combining inkjet-printing of ionomer and with electrospun Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) reinforcing nanofibers. These 12 μm thin composite membranes provided excellent thermal stability and high electrochemical performance up to 120 °C operation temperature. By anchoring CeO2 nanoparticles to the PVDF-HFP nanofibers, the open circuit voltage (OCV) degradation rate (0.39 mV/h) was found to be 3 times lower than that of a comparably thin reference Gore membrane in an OCV accelerated stress test. This poster provides an overview about our DMD activities, its future potential and gives detailed information about the possible MEA architectures feasible with DMD.
• S. Vierrath, M. Breitwieser, C. Klose, M. Klingele, R. Zengerle, S. Thiele
  Direct Membrane Deposition (DMD): Improved Power Density, Water Management and Stability
  2017 7th International Conference on ”Fundamentals & Development of Fuel Cells” in Stuttgart, 31. Januar – 2. Februar 2017
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  Kurzfassung

  Klingele et al. showed never reached high power fuel cells by applying direct membrane deposition (DMD), excelling the peak power of a catalyst coated membrane (CCM) by a factor of 2.3. To understand the underlying reasons for their high power, we identify the reasons and quantify their impact by employing electrochemical impedance spectroscopy. As a result we show, that the main reasons for the high power of DMD fuel cells are (i) a 50% reduced high frequency resistance (26 mΩcm²) due to a thinner membrane (12μm) compared to state-of-the-art and (ii) a factor 2.2 reduced mass transport losses (0.12 Ωcm²) due to increased water back diffusion through the thin membrane. A comparison of DMD vs. CCM fuel cells at the maximum power point of the CCM shows that 91% of the DMD’s improvement can be attributed to reduced mass transport losses and only 9% are caused by the reduction of the ohmic resistances.
• S. Thiele, S. Vierrath, M. Breitwieser, M. Klingele, C. Klose, R. Moroni
  Direct membrane deposition (DMD) – a new way in membrane electrode assembly manufacturing
  2017 20th Topical Meeting of the International Society of Electrochemistry, Buenos Aires/Argentinien, 19-22 März 2017
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  Kurzfassung

  The membrane is one of the very central polymer electrolyte membrane fuel cell components. At the same time it must conduct protons and inhibit transport of electrons and cross-over of reactant gases. Additionally, degradation effects have to be small to ensure a long lifetime. While traditionally consisting of pure Nafion, up to date membranes contain nanofiber reinforcements and radical scavenger packages to decrease degradation effects. Thus, seminal membranes are multi-layer, multi-component structures. In the state of the art, membrane electrode assemblies (MEA) are manufactured as catalyst coated membranes (CCMs). To form a CCM, electrodes are deposited either by the decal method, or by another deposition method. In this talk we present a novel approach for MEA manufacturing. In the so called ‘direct membrane deposition’ (DMD) approach, liquid ionomer is deposited on the catalyst layers of two gas diffusion electrodes which are successively dried and pressed together to form an MEA. Interestingly, this approach enabled power densities more than two times higher than traditional CCM based approaches which are commercially available. Also this approach allows for a simple fabrication of thin multi-layer membranes and improves the water management. DMD applied to low Pt loading electrodes revealed very high power densities per gram Pt of up to 88 kW/g Pt. An analysis of the underlying reasons for the improved performance values revealed a small influence of membrane resistance but mainly an influence in mass transport and charge transfer phenomena. In this talk we highlight our latest developments in the field of DMD based manufacturing and give an insight on degradation and durability aspects.
• M. Breitwieser, C. Klose, M. Klingele, S. Vierrath, R. Zengerle, S. Thiele
  Direct membrane deposition (DMD): A versatile fabrication technique for PEMFC composite membranes
  2017 WE-Heraeus-Seminar, Bad Honnef, 02. – 05.07.2017
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  Kurzfassung

  The conventional catalyst coated membrane (CCM) can be substituted by two ionomer-coated gas diffusion electrodes (GDE). Assembling the ionomer-coated GDEs creates a fuel cell with a very thin, directly deposited membrane (12 μm) and improved interface between membrane and electrodes. This interface has significant impact onto the fuel cell performance. Besides the increased power density, DMD bears the potential to simplify the membrane-electrode-assembly (MEA) fabrication process by successively spray-coating catalyst layer and membrane onto a gas diffusion layer. In recent work, DMD was used to fabricate composite membranes by combining inkjet-printing of ionomer and with electrospun Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) reinforcing nanofibers [3,4]. The workflow for this type of novel composite membrane is graphically summarized in Figure 1. These 12 μm thin composite membranes provided high electrochemical performance up to 120 °C operation temperature. By anchoring CeO2 nanoparticles to the PVDF-HFP nanofibers, the OCV degradation rate (0.39 mV/h) was found to be 3 times lower than that of a comparably thin reference Gore membrane in an open circuit voltage accelerated stress test according to the US department of energy (DOE.
• M. Breitwieser, M. Klingele, S. Vierrath, C. Klose, R. Zengerle, S. Thiele
  Direct membrane deposition (DMD): A versatile technique for the production of novel fuel cell composite membranes
  2017 Fuel Cells | Workshop EMEA 2017, Bad Zwischenahn, 26. - 28.06.2017
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  Kurzfassung

  The conventional catalyst coated membrane (CCM) can be substituted by two ionomer-coated gas diffusion electrodes (GDE). Assembling the ionomer-coated GDEs creates a fuel cell with a very thin, directly deposited membrane (12 µm) and improved interface between membrane and electrodes. Fuel cells fabricated with direct membrane deposition (DMD) showed record power densities of 4 W/cm² at 70°C, 300 kPa and with oxygen as fuel. Besides the increased power density, DMD bears the potential to simplify the membrane-electrode-assembly (MEA) fabrication process by successively spray-coating catalyst layer and membrane onto a gas diffusion layer. In recent work, DMD was used to fabricate composite membranes by combining inkjet-printing of ionomer and with electrospun Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) reinforcing nanofibers. The workflow for this type of novel composite membrane is graphically summarized in Figure 1. These 12 µm thin composite membranes provided excellent thermal stability and high electrochemical performance up to 120 °C operation temperature. By anchoring CeO2 nanoparticles to the PVDF-HFP nanofibers, the open circuit voltage (OCV) degradation rate (0.39 mV/h) was found to be 3 times lower than that of a comparably thin reference Gore membrane in an open circuit voltage accelerated stress test according to the US department of energy (DOE).
• S. Vierrath, M. Breitwieser, C. Klose, M. Klingele, S. Thiele
  Novel approaches to tailor the PEM|electrode interface for fuel cells with increased power density
  2017 7th Bonn Humboldt Award Winners’ Forum “Fundamental Concepts and Principles of Chemical Energy Conversion” Bonn, 11 - 15 October 2017
• M. Breitwieser, M. Klingele, S. Vierrath, R. Zengerle, S. Thiele
  Tailoring the membrane-electrode interface: A review and perspective of novel engineering approaches
  2017 Fuel Cells | Workshop EMEA 2017, Bad Zwischenahn, 26. - 28.06.2017
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  Kurzfassung

  The interface between the catalyst layer (CL) and the polymer electrolyte membrane (PEM) in a fuel cell has significant impact onto its electrochemical performance. In consequence, in the past years there have been growing research activities to engineer this interface in order to improve the performance of polymer electrolyte membrane fuel cells (PEMFCs). This talk summarizes these approaches and compares the various techniques. Based on the available fuel cell data in literature we provide a quantitative comparison of relative improvements caused by specially 3D-engineered PEM|CL interfaces. This allows to draw several conclusions: We show that the similar improvements of relevant electrochemical properties such as improved high and low frequency resistances as well as higher peak power density can be achieved by 3D PEM|CL interface engineering techniques. As an example, regardless if patterned membrane surfaces, ionomer gradients in the catalyst layer or direct membrane deposition techniques are used, comparable improvements of the fuel cell characteristics were reported. Second, for patterned membranes surfaces it was found that feature sizes of about 1-10 µm on the membrane surface seem to result in the most significant power density improvement. Finally it is shown that a re-engineered PEM│CL interface can also contribute to extend the durability of the MEA due to enhanced adhesion and contact between both functional layers.
• M. Breitwieser, M. Klingele, C. Klose, S. Vierrath, R. Zengerle, S. Thiele
  Tailoring the membrane/electrode interface - novel engineering approaches
  2017 EMEA Conference, Bad Zwischenahn, 26. - 28.06.2017

2016

• M. Breitwieser, M. Klingele, C. Klose, S. Vierrath, K. Holdcroft, S. M. Lyth, T. Bayer, B. Britton, S. Holdcroft, R. Zengerle, S. Thiele
  Direct membrane deposition (DMD): How to fabricate a high power DMD fuel cell in your lab
  2016 Gordon’s Research Conference on Fuel Cells, Stonehill College (USA), 07. - 12.08.2016
• M. Breitwieser, M. Klingele, S. Vierrath, R. Zengerle, S. Thiele
  Direkte Membrandeposition und 3D-Rekonstruktion elektro-chemischer Systeme: Aktivitäten der Porous Media Group
  2016 Fuel Cell Workshop Duisburg: „9. Workshop AiF-Brennstoffzellenallianz 2016“, Zentrum für Brennstoffzellentechnik Duisburg, 21. Juni 2016
• C. Klose, M. Breitwieser, M. Klingele, S. Vierrath, H. Cho, J. Kerres, R. Zengerle, S. Thiele
  Enhancing the ionic conductivity of directly deposited sulfonated poly(ether ketone)-Nafion composite membranes
  2016 Gordon’s Research Conference on Fuel Cells, Stonehill College (USA), 07.-12.08.2016.
• S. Vierrath, M. Breitwieser, M. Klingele, C. Klose, N. Wehkamp, R. Moroni, R. Zengerle, S. Thiele
  Polymer Electrolyte Fuel Cells Fabricated with Direct Membrane Deposition (DMD)
  2016 Prime 2016, Honolulu / Hawaii, 2-7 October 2016
• S. Vierrath, M. Breitwieser, M. Klingele, R. Zengerle, S. Thiele
  Reasons for the High Power Density of Direct Membrane Deposition Fuel Cells Revealed by Impedance Spectroscopy
  2016 MODVAL 13, Symposium for Fuel Cell and Battery Modeling and Experimental Validation, Lausanne, Schweiz (22.-23.03.2016) , Seite: 145
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  Kurzfassung

  Klingele et al. showed never reached high power fuel cells by applying direct membrane deposition (DMD), excelling the peak power of a catalyst coated membrane (CCM) by a factor of 2.3. [1] To understand the underlying reasons for their high power, we identify the reasons and quantify their impact by employing electrochemical impedance spectroscopy. As a result we show, that the main reasons for the high power of DMD fuel cells are (i) a 50% reduced high frequency resistance (26 mΩcm²) due to a thinner membrane (12µm) compared to state-of-the-art and (ii) a factor 2.2 reduced mass transport losses (0.12 Ωcm²) due to increased water back diffusion through the thin membrane (Figure 1a). A comparison of DMD vs. CCM fuel cells at the maximum power point of the CCM shows that 91% of the DMD’s improvement can be attributed to reduced mass transport losses and only 9% are caused by the reduction of the ohmic resistances (Figure 1b).
• C. Klose, M. Breitwieser, M. Klingele, S. Vierrath, H. Cho, J. Kerres, R. Zengerle, S. Thiele
  Simple fuel cell membrane fabrication by direct electrospinning and inkjet-printing
  2016 ELEN (Electrospinning for Energy), Montpellier (France), 22. - 24.06.2016

2015

• M. Klingele, M. Breitwieser, N. Wehkamp, R. Zengerle, S. Thiele
  Direct membrane deposition
  2015 EMEA Conference, Bad Zwischenahn (Germany), 22. - 24.06.2015
• M. Breitwieser, M. Klingele, R. Zengerle, S. Thiele
  Direct membrane deposition for high performance hydrogen fuel cells
  2015 ModVal, 12th Symposium on Fuel Cell and Battery Modeling and Experimental Validation. Munzingen (Germany), 26. - 27.03.2015
• M. Breitwieser, M. Klingele, B. Britton, S. Holdcroft, R. Zengerle, S. Thiele
  High power fuel cells with direct membrane deposition via ionomer spray-coating
  2015 EMEA Conference, Bad Zwischenahn (Germany), 22. - 24.06.2015
• S. Vierrath, M. Breitwieser, M. Klingele, R. Zengerle, S. Thiele
  Properties of a direct deposited membrane (DDM) Investigating the reasons for its high performance
  2015 EMEA Conference, Bad Zwischenahn (Germany), 22. - 24.06.2015
• M. Breitwieser, R. Moroni, J. Schock, M. Schulz, B. Schillinger, F. Pfeiffer, R. Zengerle, S. Thiele
  Studying the water evolution in direct membrane deposition PEM fuel cells via in-situ neutron imaging
  2015 ModVal, 12th Symposium on Fuel Cell and Battery Modeling and Experimental Validation. Munzingen (Germany), 26. - 27.03.2015