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Journal articles on the topic "Ionomr AEMION"
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Mardle, Peter, Zhengming Jiang, Zhiqing Shi, and Steven Holdcroft. "(Invited) Anion Exchange Membrane and Ionomer Development for Electrochemical CO2 Reduction." ECS Meeting Abstracts MA2022-01, no. 39 (2022): 1767. http://dx.doi.org/10.1149/ma2022-01391767mtgabs.
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Recent developments have proven the economic potential of electrochemical reduction of CO2 to value added chemicals, where single cells are now capable of achieving high energetic efficiencies at industrially relevant current densities. 1 These advances are in no small part due to the increased ionic conductivity, hydroxide stability and commercial availability of anion exchange membranes (AEMs). However, there currently exists little understanding as to how these materials affect the efficiency of CO2 conversion devices because the research community is only now beginning to understand the variety and complexity of the transport processes involved. 2 In collaboration with Ionomr Innovations Inc. and the National Research Council of Canada, and as part of the Energy for Clean Materials Challenge Program, we have made advances in the understanding of how AEM properties affect device performance and how we can develop materials tailor-made for CO2 electrolyser technology. Here, we demonstrate the development of a zero-gap single cell design, utilizing first generation Aemion® materials for the conversion of CO2 to CO with an energetic efficiency of 40% at 200 mA cm-2. 3 Despite the initially high energetic efficiency, we demonstrate how the crossover of carbonate dianions results in the reduction of anolyte pH and deconvolute how this results in a diminished cell efficiency over extended operation. From this, we show how functionalization of the polymer electrolyte structure can reduce this degradation mechanism while retaining high energetic efficiencies. In addition, we demonstrate how under milder electrolysis conditions, the total cell efficiency has a significant dependency on the flux of alkali metal cationic species from the supporting anolyte to the cathode. We show that due to the large promotion effect of cations for the electrochemical CO2 reduction, AEM design not only influences ohmic resistances in the cell, but also greatly affects the charge transfer resistance (RCT) of the cathode to a much greater extent than other electrochemical conversion devices. We thus make correlations between water permeability and perm-selectivity of AEMs to the overall CO2 conversion efficiency. We then discuss the incorporation of anion exchange ionomers in the cathode catalyst layer of CO2 electrolysis cells and how the ionomer parameters define the efficiency and selectivity of Ag catalysts towards electrochemical CO2 reduction. Through this work, we demonstrate the influencing factors of AEM and ionomer materials on the efficiency of electrochemical CO2 conversion and conclude that further advances are paramount for the adoption of this promising technology, which is integral in closing the carbon loop of the petrochemical industry and meeting our wider climate change targets. References: P. De Luna et al., Science, 364, eaav3506 (2019). D. Salvatore, C. Gabardo, A. Reyes, and S. Holdcroft, Nat. Energy, 6, 339–348 (2021). P. Mardle, S. Cassegrain, F. Habibzadeh, Z. Shi, and S. Holdcroft, J. Phys. Chem. C, 125, 25446–25454 (2021). Figure 1
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Eitzen, Jasper, Jake Mouallem, Scott Storbakken, Andrea Quintero, and Marc Secanell. "Experimental and Numerical Analysis of Alkaline Exchange Membrane Water Electrolyzers." ECS Meeting Abstracts MA2024-02, no. 45 (2024): 3168. https://doi.org/10.1149/ma2024-02453168mtgabs.
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The operation of fuel cells and electrolyzers in alkaline conditions allows for the use of: i) less expensive electrocatalyst, such as nickel alloys and silver, ii) cheaper metals for porous layers and bipolar plates due to the less corrosive environment at high pH, e.g., nickel and stainless steel compared to titanium in PEMWE; and, iii) seawater for electrolysis [1]. However, it is only in the past decade that remarkable strides in polymer synthesis and stabilization techniques have enabled the fabrication of AEMs and ionomers that are stable at high pH and above 80oC, and have ionic conductivities as high as the standard PEM materials. Currently, several commercial AEMs and ionomers are available, e.g., Ionomr Aemion (hexamethyl-p-terphenyl poly(benzimidazolium)), Versogen and Sustanion. AEMWEs have demonstrated remarkable power and current densities, e.g., 2 A/cm2 at 1.8 V using 1 M KOH [2] and and 1 A/cm2 at 1.8 V using pure water and PGM-free catalysts [3]. Molero-Gonzalez et al. [4] also demonstrated AEMWE degradation rates of 13 μV/h over 8,900 h at a current density of 600 mA cm−2. Research however is still needed for the development of AEMWE with low-PGM and PGM-free electrodes that are able to operate over a wide range of operating conditions, e.g., alkalinity, temperature, pressure and low flow rate and with high durability. The development of these systems necessitates research and development in the areas of electrode fabrication, characterization, testing and numerical simulation to highlight the most critical limiting kinetic and transport processes in a wide range of available AEMs and catalysts. In this presentation, catalyst coated membranes (CCMs) fabricated in-house by inkjet printing using platinum and iridium as the cathode and anode catalysts onto reinforced Aemion+ membranes are assessed for their performance under a variety of feed methods. Three possible feed configurations are investigated: two-electrode feed, anode-only feed, and cathode-only feed, using a 1 M KOH solution as feedstock. These CCMs resulted in a performance of 0.9 A/cm2 at 2 V in two-electrode and anode-only feed configurations, but under cathode-only feed, the performance decreased to 0.55 A/cm2 at 2 V, as shown in the figure. Therefore, supplying electrolyte only to the anode does not lead to any performance penalties and eliminates the need for a gas separation unit. Short-term stability was also acceptable for anode-only and two-electrode feed but suffered under cathode-only feed. This performance disparity was not caused by an increase in membrane resistance, as the measured high frequency resistance did not change significantly. A reference electrode was integrated into the cell hardware to investigate the reasons for the difference in performance, finding that the poor cathode-only feed performance was largely caused by an increase in the anode overpotential. A two-dimensional AEMWE model was also developed to further analyze experimental results, and study ion and reaction distribution in each electrode, as well as the sensitivity of AEMWE performance on KOH concentration. Reference [1] Du et al. Chemical Reviews, 122 (13):11169-11896, 2022. [2] Fortin et al. Journal of Power Sources, 451:227814, 2020. [3] Li et al., Nature Energy, 5:378-385, 2020. [4] Molero-Gonzalez et al. Journal of Power Sources Advances 19:100109, 2023. Figure 1
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Liu, Jiafei, and Marc Secanell. "Exploring the Impact of Cathode Ionomer Content on Alkaline Exchange Membrane Fuel Cells (AEMFCs) Using Inkjet Printing Technique." ECS Meeting Abstracts MA2024-02, no. 44 (2024): 3019. https://doi.org/10.1149/ma2024-02443019mtgabs.
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Hydrogen proton exchange membrane fuel cells (PEMFCs) typically rely on expensive platinum group metals (PGMs) as catalysts. A promising strategy to eliminate the need for PGM catalysts is to operate the cell under alkaline conditions. Non-PGM based AEMFCs have achieved power densities exceeding 1 W/cm2, and various commercial electrolytes, such as Tokuyama A201/A901/AS-4, FumaTech Fumasep, Ionomr Aemion, and Versogen PiperION, have been developed and are available for researchers to explore and enhance AEMFC performance. Unfortunately, AEMFCs using commercial materials have not yet demonstrated performance and stability comparable to PEMFCs even though their ion transport properties are similar. Therefore, there is a need to study the physical processes that are limiting the performance of these materials in AEMFC membrane electrode assemblies (MEAs). AEMFCs electrode performance is very sensitive to a myriad of factors with two key factors being: a) the fabrication method; and b) ionomer to catalyst ratio. Regarding the former, unlike in PEMFCs, the number of fabrication techniques studied to fabricate AEMFC electrodes in the literature has been limited with only a handful of studies utilizing techniques such as ultrasonic spray-coating and doctor blade to control the catalyst layer structure. The development of novel fabrication techniques would therefore help the development of these technologies and allow more systematic studies to be performed, such as a detailed analysis of the ionomer to catalyst ratio. Even though previous research already showed the sensitivity of AEMFC performance to variations in ionomer content [2,4-6,11,17], its influence at varying temperatures and with newly developed commercial materials has not been thoroughly investigated. Furthermore, its effect on cell stability has not received sufficient attention. In this work, inkjet printing is introduced as a novel fabrication method for AEMFC electrode fabrication and applied to fabricate low-loading PGM-based CCMs with varying and graded cathode ionomer loading for AEMFCs. The inkjet-printed CCMs were tested in operating AEMFCs with H2/O2 at 60 °C, demonstrating a cell power density of 0.53 W/cm2 with a total loading of 0.3 mgPt/cm2, one of the highest reported in the literature using commercial materials (see figure), along with high repeatability and stability. The effect of cathode ionomer content and grading was studied at 60 °C and 80 °C with 90% RH inlet gases. The optimal cathode ionomer content at the beginning of life was identified as 20 wt% under both conditions, but the cell experienced unstable performance over time at 80 °C, with a decrease in cell voltage during constant current holds. Adding more ionomer to the cathode decreased the rate of cell degradation, which we hypothesize is due to increased water retention. The graded cathode, with more ionomer close to the AEM, appears to be the best strategy to minimize the observed instability. [1] T. Reshetenko et al., Journal of Power Sources 375 (2018) 185–190. [2] R. B. Kaspar et al., Journal of the Electrochemical Society 162 (6) (2015) F483. [3] D. Yang et al., Chinese Journal of Catalysis 35 (7) (2014) 1091–1097. [4] D. Yang et al., Journal of Power Sources 267 (2014) 39–47. [5] A. Carlson et al., Electrochimica Acta 277 (2018) 151–160. [6] X. Xie et al., International Journal of Energy Research 43 (14) (2019) 8522–8535. [7] P. S. Khadke and U. Krewer, Electrochemistry Communications 51 (2015) 117–120. [8] B. Britton and S. Holdcroft, Journal of The Electrochemical Society 163 (5) (2016) F353. [9] J. Zhang et al., Cell Reports Physical Science 2 (3). [10] D. Sebastian et al., Catalysts 10 (11) (2020) 1353. [11] S. Kim et al., Electrochimica Acta 400 (2021) 139439. [12] I. Gatto et al., ChemElectroChem 10 (3) (2023) e202201052. [13] N. U. Saidin et al., Asia-Pacific Journal of Chemical Engineering e3024.21 [14] V. M. Truong et al., Materials 12 (13) (2019) 2048. [15] T. Novalin et al., Journal of Power Sources 507 (2021) 230287. [16] Q. Wei, et al., Sustainable Energy & Fuels 6 (15) (2022) 3551–3564. [17] J. Hyun et al., Journal of Power Sources 573 (2023) 233161. [18] E. Sediva et al., Journal of Power Sources 558 (2023)232608. Figure 1
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Chuluunbandi, Khajidkhand, Simon Thiele, and Anna T. S. Freiberg. "Comparison of Different Ionomers for the Anode Catalyst Layer of Anion Exchange Membrane Water Electrolysis." ECS Meeting Abstracts MA2024-02, no. 45 (2024): 3148. https://doi.org/10.1149/ma2024-02453148mtgabs.
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In water electrolysis cells, optimizing the anode electrode where the oxygen evolution reaction takes place is crucial for high performance and durability. The ionomer is an essential part of the catalyst layer (CL). It provides ionic conductivity, enabling ions to move to the catalyst sites where the electrochemical reaction occurs. Additionally, ionomers contribute to tuning the hydrophobicity and hydrophilicity of the CL, which influences water availability at catalyst sites and gas removal. Moreover, ionomers ought to help to maintain optimal pH levels, an important factor for catalyst stability. In anion exchange membrane water electrolysis (AEMWE), when a supporting electrolyte is used, the ionic conduction takes place not only via the ionomer but also via the supporting electrolyte. Therefore, many studies in AEMWE use NafionTM as an ionomer even though it is a cation exchange ionomer.1, 2 Also, several studies use polytetrafluoroethylene (PTFE) as a binder.3, 4 Thus, in this study, different commercial ionomers/binder are compared for the usage on the anode side of the AEMWE to understand their influence on the performance of the AEMWE cell at different pH feed electrolytes (1M, 0.1M and 0.01M); Hydrophilic cation exchange Nafion™, hydrophilic anion exchange Aemion® and PiperION®, and hydrophobic inert PTFE are used in the Ir-based anode CL. A commercial anion-exchange membrane (PiperION®) and a Pt/C cathode with PiperION® ionomer are used, respectively. CL compositions and morphologies are investigated via thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Electrochemical characterizations such as polarization curve and constant current hold analysis along with electrochemical impedance spectroscopy (EIS) are performed on a full cell set up to assess the performance, durability, and ionic transport resistance of the anode CL. We show that anionic ionomers (Aemion® and PiperION®) do not lead to a better performance of the cell at 1M KOH concentration (see figure) and even at lower concentrations such as 0.1M KOH. Nafion™ ionomer incorporated membrane electrode assemblies (MEAs) exhibit better performance than anionic ionomers (Aemion® and PiperION®) and inert binder (PTFE) in 1M KOH measurement. One hypothesis on Nafion’s TM outstanding performance is that Nafion’s TM anionic head groups form an ionic interaction with the cationic head groups of the PiperION membrane and therefore lower the contact resistance between CL and membrane.5 However, in our measurements, all high-frequency resistances of different ionomers/binder incorporated MEAs are in the same range (55-65 mΩ cm-2), which opposes the hypothesis. Based on the overall polarization characteristics, the performance for the different ionomers changes mainly in the kinetic region. As this difference can already be observed at begin of life where ionomer decomposition can be neglected, we assign this difference to an ionomer-catalyst interaction phenomenon (i.e., poisoning effect) or to a structural change in the CL when using different ionomers. Nafion’s ™ swelling in 1M KOH solution is lower than anionic ionomers. Therefore, it might be influencing the performance by having the optimal triple phase boundary and not blocking some of the catalyst particles. However, the PTFE binder also doesn’t swell in the KOH solution, but the performance is worse than for the Nafion™-based anode CL. By a variation of testing parameters (KOH feed molarity, temperature) and ink/CL fabrication we discuss the possible reasons for this phenomenon. In general, the role of ionomers for AEMWE must be reevaluated as the ionic conductivity of anion exchange ionomers becomes irrelevant when supporting electrolyte is in use, and anion exchange ionomers do not follow the same design criteria as for proton exchange ionomers. References M. Moreno-González, P. Mardle, S. Zhu, B. Gholamkhass, S. Jones, N. Chen, B. Britton and S. Holdcroft, Journal of Power Sources Advances, 19, 100109 (2023). I. V. Pushkareva, A. S. Pushkarev, S. A. Grigoriev, P. Modisha and D. G. Bessarabov, Int. J. Hydrog. Energy, 45(49), 26070–26079 (2020). C. C. Pavel, F. Cecconi, C. Emiliani, S. Santiccioli, A. Scaffidi, S. Catanorchi and M. Comotti, Angewandte Chemie International Edition, 53(5), 1378–1381 (2014). M. K. Cho, H.-Y. Park, H. J. Lee, H.-J. Kim, A. Lim, D. Henkensmeier, S. J. Yoo, J. Y. Kim, S. Y. Lee, H. S. Park and J. H. Jang, J. Power Sources, 382, 22–29 (2018). B. Mayerhöfer, K. Ehelebe, F. D. Speck, M. Bierling, J. Bender, J. A. Kerres, K. J. J. Mayrhofer, S. Cherevko, R. Peach and S. Thiele, J. Mater. Chem. A, 9(25), 14285–14295 (2021). Figure 1
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Nallayagari, Ashwini Reddy, Frédéric Murphy, Maria Luisa Di Vona, and Elena Baranova. "Investigation of Electrocatalyst and Ionomer Interaction in Anion Exchange Membrane Water Electrolysis." ECS Meeting Abstracts MA2023-02, no. 42 (2023): 2067. http://dx.doi.org/10.1149/ma2023-02422067mtgabs.
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Anion exchange membrane water electrolysis (AEMWE) is a type of electrolysis that involves the use of an anion exchange membrane (AEM) to separate the anode and cathode compartments. During the electrolysis process, water is split into hydrogen gas (H2) at the cathode and oxygen gas (O2) at the anode. AEMWE is an emerging technology that has the potential to play a significant role in the production of green hydrogen, which is a promising energy carrier for a variety of applications, including fuel cells and transportation. One of the benefits of AEMWE is that it can be used with a variety of water sources, including seawater and wastewater. Additionally, AEMWE has the potential to be more energy-efficient and cost-effective than other types of water electrolysis because it can operate at lower voltages and use cheap Ni-based materials [1]. Recently, there has been a significant amount of interest in the development of anion exchange ionomers (AEI) that conduct hydroxide ions [2]. We recently investigated the PPO-LC-TMA ionomer (poly(2,6-dimethyl-1,4-phenylene oxide) [3] backbone with amine-functionalized by trimethyl amine) [4] as an ionomer for Ni-based catalysts in AEMWE. Commercial Aemion, Fumion, and Nafion AEI were compared to the lab-synthesized ammonium-enriched anion exchange ionomer PPO-LC-TMA as an anode catalyst layer for oxygen evolution reaction (OER). Cyclic voltammetry results showed that the NiFe catalyst layer with PPO-LC-TMA AEI showed higher Ni(OH)2/NiOOH peak current density, while current density obtained over Ni90Fe10 catalysts was 11%, 17%, and 39% for Nafion, Fumion, and Aemion AEI, respectively [5]. This resulted in increased OER activity of Ni90Fe10 with PPO-LC-TMA AEI and a lower overpotential of 151 mV at 10 mA cm-2 in 1 M KOH. Ex-situ Raman spectroscopy of as prepared and spent catalytic layer confirmed that the electrode transitioned to the Ni-OOH phase after polarization. NiFe anode catalytic layers were tested in a 5 cm2 single-cell alkaline membrane water electrolysis (AEMWE) with varying amounts of PPO-LC-TMA (7, 15, and 25 wt %). AEMWE results revealed that 25 wt% PPO-LC-TMA is the best ionomer loading, achieving a cell voltage of 1.941 V at 600 mA cm-2 in 1 M KOH at 50°C. Both three-electrode electrochemical cell and alkaline membrane water electrolysis (AEMWE) tests revealed that the PPO-LC-TMA ionomer stabilized NiFe catalyst and improved its performance compared to Fumion and Nafion ionomers. These results will be presented and discussed, along with details of electrochemical and physical characterizations. References E. Cossar, F. Murphy, E.A. Baranova, J Chem Technol Biotechnol, 97 (2022) 1611–1624. Wright, A. G.; Fan, J.; Britton, B.; Weissbach, T.; Lee, H.-F.; Kitching, E. A.; Peckham, T. J.; Holdcroft, S. Energy Environ. Sci. 9 (2016) 2130−2142. A.R. Nallayagari, E. Sgreccia, L. Pasquini, M Sette, P. Knauth and M. L. Di Vona ACS Appl. Mater. Interfaces, 14, 41 (2022) 46537–46547. R.-A. Becerra-Arciniegas, R. Narducci, G. Ercolani, E. Sgreccia, L. Pasquini, M. L. Di Vona, and P. Knauth, J. Phys. Chem. C, 124, 2 (2020) 1309–1316. E. Cossar, F. Murphy, J. Walia, A. Weck, E.A. Baranova, ACS Applied Energy Materials, 5 (2022) 9938−9951.
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Jansonius, Ryan, Marta Moreno, and Benjamin Britton. "High Performance AEM Water Electrolysis with Aemion® Membranes." ECS Meeting Abstracts MA2022-01, no. 39 (2022): 1723. http://dx.doi.org/10.1149/ma2022-01391723mtgabs.
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By 2030 up to 50% of energy is expected to be carried in the bonds of H2. Global electrolysis capacity must increase from the current 240 MW to an anticipated 300 GW in 2030 and 3500 GW in 2050 to enable this transition. Alkaline and PEM electrolyzers are commercially mature with the currently market share of new installations roughly an equal split between these technologies. However, each of these electrolyzers are associated with challenges – alkaline electrolyzers operate at low current density, and require high concentration electrolytes (30 wt% KOH) to conduct hydroxides through the porous electrode separator (I.e., Zirfon). PEM electrolyzers use a proton conductive membrane to enable high current densities, however, running the reaction in acidic electrolyte requires platinum group catalysts and component coatings that hinder scalability at 2050 targets. AEM water electrolyzers address both of these challenges by pairing anion exchange membrane with alkaline electrolyte to enable high current density operation, at high pressure, without noble metal catalysts. These attributes enable the most cost-effective green hydrogen - bringing the DOE hydrogen shot target of $1/kg within reach. Anion exchange membrane chemistries have previously hindered this type of electrolyzer – AEMs based on quaternary amines, or pendant imidazolium groups chemically degrade in concentrated alkaline electrolyte, and mechanically degrade (from swelling) in low concentration alkaline media. Ionomr’s Aemion+ membranes are based on a sterically-protected polybenzimidazole chemistry and are chemically robust (stable in up to 10 M KOH), and exhibit low swelling to enable operation in low concentration electrolytes. These membranes are an enabling technology for long duration water and CO2 electrolysis. This talk highlights how Ionomr’s Aemion+ membranes enable performance in excess of 1 A/cm2 at 1.8 V with non-PGM catalysts and a variety of configurations, and >4000 hours of durability in continuous operation. Figure 1
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Turtayeva, Zarina, Feina Xu, Régis Peignier, Alain Celzard, and Gael Maranzana. "Optimization of Ionomer Content in Membrane Electrode Assemblies and Its Impact on the Performance in Anion Exchange Membrane Fuel Cells." ECS Meeting Abstracts MA2022-02, no. 43 (2022): 1624. http://dx.doi.org/10.1149/ma2022-02431624mtgabs.
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Anion exchange membrane fuel cells (AEMFCs) have recently attracted significant attention as low-cost alternative fuel cells to traditional proton exchange membrane fuel cells due to the possible use of platinum-group metal-free electrocatalysts [1]. Over the past decade, new materials dedicated to the alkaline medium, such as anion exchange membranes (AEMs) and anion exchange ionomers (AEIs), have been developed and studied in AEMFCs [2, 3]. However, only a few AEMs and AEIs are commercially available, and there are not ready to use catalyst coated membranes (CCMs) and/or gas diffusion electrodes (GDEs) with the wished AEMs or AEIs. In order to manufacture CCMs and/or GDEs on the basis of commercial materials, catalyst inks need to be prepared before testing them in AEMFC. It is well known that the composition of catalytic ink and the way to deposit it can influence the interaction between solvent, ionomer and catalyst particles during solvent evaporation and thus on the final structure and morphology of the catalyst layer. However, there are only a few papers dealing with catalyst layer compositions and structures for AEMFCs [4, 5], probably due to the recent development of alkaline fuel cells and new dedicated materials such as AEM and AEI. Since the ionomer/catalyst particle interface plays a crucial role in electrochemical reactions, it is essential to understand the impact of ionomer content on AEMFC performance as well as on water management. For this purpose, catalytic inks were prepared with different amounts of ionomer, ranging from 13 to 33 % in ratio. During this work, Pt / C (40 % in wt) catalyst as well as Aemion® membranes and ionomers were used. Different CCMs and GDEs were manufactured at 60 °C using a commercial ultrasonic spray coating bench. The morphology of the catalyst layers was characterized by scanning electron microscopy, and the thickness of the deposition was measured by a profilometer. Before testing in AEMFC, all prepared samples and membranes were converted to OH- form for 48 h in KOH 3M (the solution was changed every 12h). The performance of the prepared CCMs and GDEs was studied in a home-made AEMFC bench after an activation step. The results shown in Fig.1 highlight that: (i) the ionomer content in the catalyst layers affects the performance of the fuel cell, regardless of the coated support (membrane or GDL), (ii) concerning CCMs-based MEAs, the lower the ionomer content, the better the performance via the polarization curve, (iii) CCMs and GDEs-based MEAs do not behave similarly, (iv) GDEs-based MEAs show high OCV and high voltage for a given current density in comparison with CCMs-based MEAs, (v) concerning GDEs-based MEAs, the variation of the ionomer content in catalyst layer affects less the OCV value than the water management, and (vi) the water management of GDEs-based MEAs seems depend on the relative humidity of both gases and ionomer content in catalyst layers. This work is still under investigation. We will attempt to understand the relationship between the membrane/ionomer under different relative humidity and gas flow rates. [1] H. A. Firouzjaie and W. E. Mustain, “Catalytic Advantages, Challenges, and Priorities in Alkaline Membrane Fuel Cells,” ACS Catal., pp. 225–234, 2019, doi: 10.1021/acscatal.9b03892. [2] J. R. Varcoe et al., “Anion-exchange membranes in electrochemical energy systems †,” 2014, doi: 10.1039/c4ee01303d. [3] N. Chen and Y. M. Lee, “Anion exchange polyelectrolytes for membranes and ionomers,” Prog. Polym. Sci., vol. 113, p. 101345, Feb. 2021, doi: 10.1016/j.progpolymsci.2020.101345. [4] J. Hyun et al., “Tailoring catalyst layer structures for anion exchange membrane fuel cells by controlling the size of ionomer aggreates in dispersion,” Chem. Eng. J., vol. 427, no. August 2021, 2022, doi: 10.1016/j.cej.2021.131737. [5] P. Santori, A. Mondal, D. Dekel, and F. Jaouen, “The critical importance of ionomers on the electrochemical activity of platinum and platinum-free catalysts for anion-exchange membrane fuel cells,” R. Soc. Chem., vol. 2020, no. 7, pp. 3300–3307, doi: 10.1039/d0se00483aï. Figure 1
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Koch, Susanne, Philipp A. Heizmann, Sophia K. Kilian, et al. "The effect of ionomer content in catalyst layers in anion-exchange membrane water electrolyzers prepared with reinforced membranes (Aemion+™)." Journal of Materials Chemistry A 9, no. 28 (2021): 15744–54. http://dx.doi.org/10.1039/d1ta01861b.
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Britton, Benjamin, and Marta Moreno. "(Invited) Aemion+® AEM Water Electrolysis with Excellent Iridium-Free Performance and Industrially Relevant Stability in Hot, Caustic Electrolyte." ECS Meeting Abstracts MA2023-01, no. 36 (2023): 2031. http://dx.doi.org/10.1149/ma2023-01362031mtgabs.
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Hydrogen has a unique ability to maximize the utility of and enable new business models for intermittent renewable deployment. It can be stored cost-effectively in geological storage, transported between regions to suit geographic needs and bridge Dunkelflautes. Global electrolysis capacity must increase from the current <2 GW to 850 GW in 2030 (IEA Net Zero 2050) and in excess of 3500 GW in 2050 to enable this transition. Both traditional Alkaline (AWE) and proton-exchange membrane electrolyzers (PEMWE) are mature technologies that are anticipated to split the overall market share. However, each of these technologies face fundamental challenges: AWE operate at low current density, requiring large and difficult to transport systems, require high concentration electrolytes (e.g. 30 wt% KOH) to conduct hydroxides and ensure low gas solubilities for safety, which necessitates the use of expensive and difficult to machine high-nickel steels, especially in advanced, pressurized designs. Additionally, the porous nature of the electrode separator (e.g. Zirfon) compromises the desired dynamic load for pairing with intermittent renewables. PEMWE use a proton-conductive membrane to enable high current densities, dynamic loads, and differential hydrogen pressures, however, the most efficient operation requires iridium catalyst, which presents a near-term challenges with scalability, together with Ti and PGM structural elements that further impede cost-effectiveness. Alkaline anion-exchange water electrolyzers (AEMWE) address both of these challenges by operating with a cohesive, hydroxide-transporting membrane together with alkaline electrolyte to enable high efficiency, high current density operation, without iridium electrocatalysts or other scarce or expensive components. The realization of capital cost-effectiveness, dynamic load, and compact systems in one technology enables the most cost-effective green hydrogen and represents a step-change in the trajectory towards the DOE Hydrogen Shot target of $1/kg. The instability of alkaline anion exchange membrane chemistries based on quaternary amines or pendant imidazolium groups in relevant temperatures and alkalinities to industrial operations have historically resulted in untenable compromises and too-short lifetimes for industrial-scale deployment. Ionomr's Aemion+® AF2-AWP8-75-X and AF3-HWK9-75-X membranes are based on a sterically-protected imidazolium chemistries that are chemically robust (e.g. 6 months, 1 M, 80 °C without alteration to chemical or mechanical properties), and additionally exhibit low swelling to provide mechanical integrity to electrodes and enable operation in low concentration electrolytes. These membranes are an enabling technology for long-duration AEM water electrolysis. This talk highlights how Ionomr's Aemion+® membranes demonstrate target performances (e.g. >2 A/cm² at 2 V) with non-PGM OER catalysts with no apparent losses to 1000 hours operation across several configurations at ≥70 °C and 1 M KOH operation, and several longer lifetime demonstrations including 1 year durability using AWE electrodes and >6 months including hydrogen crossover measurement. This talk further highlights the potential for the three-dimensionality of electrodes in alkaline AEMWE and the necessary processing and operational requirements to create reproducible and stable GDEs with catalyst ink-based deposition techniques. Figure 1
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Hagner, Luis, Lukas Metzler, Susanne Koch, et al. "AEM Water Electrolysis with Ni-Based Catalysts and Tailored Poly(arylene piperidinium) Materials for Improved Stability." ECS Meeting Abstracts MA2024-01, no. 40 (2024): 3097. http://dx.doi.org/10.1149/ma2024-01403097mtgabs.
Full textAbstract:
Anion-exchange membrane water electrolysis (AEMWE) is a promising low-temperature technology for hydrogen production. It leverages the advantages of the currently dominant technologies (alkaline water electrolysis and proton-exchange membrane water electrolysis) by using transition metal group based catalysts and a zero-gap configuration, enabling high efficiency. However, current AEMWE systems show a limited stability and efficiency. In this work, commercial and non-commercial polymers are used to fabricate catalyst-coated membranes with a production method oriented towards scalable production (1). A tailored poly(arylene piperidinium) polymer (PAP) shows enhanced stability compared to commercial Aemion+TM during 100 h operation at 1 A/cm2 and 60 °C in 1 M KOH electrolyte (Figure 1) (2). Additionally, different anode catalysts are employed and measured in a reference electrode setup to separate the cell voltage into contributions from the anode and cathode (3). Here, the overpotential of Ni(OH)2 is higher compared to the more active NiFe-layered-double-hydroxide(LDH) and iridium oxide. Employing this setup to measure individual degradation of cathode and anode is part of ongoing research. Figure 1. a) Tailored PAP material compared to Aemion+TM based systems operated at 1 A/cm2 showing a linear degradation of ca. 400 µV/h. b) Polarization curves of AEMWE single cells with different anode catalysts, measured with an integrated reference electrode setup, which allows to distinguish anode and cathode contribution to the cell voltage. Measured at 60 °C in 1 M KOH electrolyte, 5 cm2 cell area. References Koch, S.; Metzler, L.; Kilian, S. K.; Heizmann, P. A.; Lombeck, F.; Breitwieser, M.; Vierrath, S. Toward Scalable Production: Catalyst‐Coated Membranes (CCMs) for Anion‐Exchange Membrane Water Electrolysis via Direct Bar Coating. Advanced Sustainable Systems 2023, 7 (2). DOI: 10.1002/adsu.202200332. Weber, R.; Klingenhof, M.; Koch, S.; Metzler, L.; Merzdorf, T.; Meier-Haack, J.; Strasser, P.; Vierrath, S.; Sommer, M. Meta -kinks are key to binder performance of poly(arylene piperidinium) ionomers for alkaline membrane water electrolysis using non-noble metal catalysts. J. Mater. Chem. A [Online] 2024, 12 (13), 7826–7836. Xu, Q.; Oener, S. Z.; Lindquist, G.; Jiang, H.; Li, C.; Boettcher, S. W. Integrated Reference Electrodes in Anion-Exchange-Membrane Electrolyzers: Impact of Stainless-Steel Gas-Diffusion Layers and Internal Mechanical Pressure. ACS Energy Lett. [Online] 2021, 6 (2), 305–312. Figure 1