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1
Borm, Oliver, and Stephen B. Harrison. "Reliable off-grid power supply utilizing green hydrogen." Clean Energy 5, no. 3 (2021): 441–46. http://dx.doi.org/10.1093/ce/zkab025.
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Abstract Green hydrogen produced from wind, solar or hydro power is a suitable electricity storage medium. Hydrogen is typically employed as mid- to long-term energy storage, whereas batteries cover short-term energy storage. Green hydrogen can be produced by any available electrolyser technology [alkaline electrolysis cell (AEC), polymer electrolyte membrane (PEM), anion exchange membrane (AEM), solid oxide electrolysis cell (SOEC)] if the electrolysis is fed by renewable electricity. If the electrolysis operates under elevated pressure, the simplest way to store the gaseous hydrogen is to feed it directly into an ordinary pressure vessel without any external compression. The most efficient way to generate electricity from hydrogen is by utilizing a fuel cell. PEM fuel cells seem to be the most favourable way to do so. To increase the capacity factor of fuel cells and electrolysers, both functionalities can be integrated into one device by using the same stack. Within this article, different reversible technologies as well as their advantages and readiness levels are presented, and their potential limitations are also discussed.
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Alkayyali, Tartela, Ali Shayesteh, Harrison Mar, et al. "Utilizing Direct Membrane Deposition to Improve the Performance of Forward-Bias Bipolar Membrane CO2 Electrolysers." ECS Meeting Abstracts MA2023-02, no. 1 (2023): 67. http://dx.doi.org/10.1149/ma2023-02167mtgabs.
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The electrochemical conversion of CO2 to multi-carbon products (C2+), such as ethylene and ethanol, is an attractive technology towards achieving net zero carbon emission goals. Among the available configurations of CO2 electrolysers, those employing a bipolar membrane (BPM) in forward-bias mode (f-BPM) reduce CO2 loss to the anode – a problem commonly faced in traditional anion exchange membrane (AEM) electrolysers. Therefore, carbon efficiency (the percent of input CO2 that is converted to C2+ products) and system operational costs can be improved. In f-BPM electrolysers, (bi)carbonate ions move through the AEM then combine with protons moving through the cation exchange membrane (CEM) to regenerate CO2 and H2O at the AEM|CEM interface. Recent reports have implemented a porous AEM structure or an added AEM|CEM interface channel to aid the movement of CO2 from the AEM|CEM interface to the cathode and, thus, avoid blistering. Despite the advantage of f-BPM CO2 electrolysers, their performance is limited by the parasitic H2 evolution reaction (>20% Faradaic efficiency, or FE) and the low C2+ FE (<40%) at industrially relevant reaction rates (≥200 mA cm-2). We attribute this performance limitation to the unintended gaps between the used AEM and CEM. Inadequate contact between the AEM and CEM is anticipated to reduce the extent of local CO2 regeneration and promote unwanted proton crossover to the cathode; both phenomena could be contributing to the commonly observed FEs. In this report, we enhanced the contact between the AEM and CEM through the use of direct membrane deposition (DMD) over a Cu-based cathode. The DMD approach enabled modular control over the AEM and CEM thicknesses and structures, which improved ion and gas transport. Through electrochemical impedance spectroscopy, the DMD system was observed to improve the mass transport by >58% compared to a system that is similar to current f-BPM electrolysers (i.e., control system). The facilitated mass transport resulted in a reduction of the operating cell potential (by 0.84 V) and an enhancement of the C2+ FE to 65% (from 29% in the control system) at 300 mA cm-2. The flexibility of the DMD approach also enabled the fabrication of asymmetric BPMs, resulting in a record low H2 FE of 12% at 300 mA cm-2. We also demonstrated a 79% single-pass CO2 conversion (SPC) with 67% C2+ FE, resembling the highest simultaneous SPC and C2+ FE achievement at high current density (300 mA cm-2)among current f-BPM electrolysers. The DMD benefit was also applicable to other types of CO2 electrolysers, such as CO2-to-CO silver catalyst electrolysers, in which the CO FE was boosted to 90% (from 65% in the control system) at 90 mA cm-2. Figure 1
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Discepoli, Gabriele, Silvia Barbi, Massimo Milani, Monia Montorsi, and Luca Montorsi. "Investigating Sustainable Materials for AEM Electrolysers: Strategies to Improve the Cost and Environmental Impact." Key Engineering Materials 962 (October 12, 2023): 81–92. http://dx.doi.org/10.4028/p-7rkv7m.
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In recent years, the EU policy identified the hydrogen as one of the main energy vectors to support the power production from renewable sources. Coherently, electrolysis is suitable to convert energy in hydrogen with no carbon emission and high purity level. Among the electrolysis technologies, the anion exchange membrane (AEM) seems to be promising for the performance and the development potential at relatively high cost. In the present work, AEM electrolysers, and their technological bottlenecks, have been investigated, in comparison with other electrolysers’ technology such as alkaline water electrolysis and proton exchange membranes. Major efforts and improvements are investigated about innovative materials design and the corresponding novel approach as main focus of the present review. In particular, this work evaluated new materials design studies, to enhance membrane resistance due to working cycles at temperatures close to 80 °C in alkaline environment, avoiding the employment of toxic and expensive compounds, such as fluorinated polymers. Different strategies have been explored, as tailored membranes could be designed as, for example, the inclusion of inorganic nanoparticles or the employment of not-fluorinated copolymers could improve membranes resistance and limit their environmental impact and cost. The comparison among materials’ membrane is actually limited by differences in the environmental conditions in which tests have been conducted, thereafter, this work aims to derive reliable information useful to improve the AEM cell efficiency among long-term working periods.
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Garcia-Osorio, Dora Alicia, Hansaem Jang, Bhavin Siritanaratkul, and Alexander Cowan. "Water Dissociation Interfaces in Bipolar Membranes for H2 Electrolysers." ECS Meeting Abstracts MA2023-02, no. 39 (2023): 1891. http://dx.doi.org/10.1149/ma2023-02391891mtgabs.
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In order to meet large scale energy demands in a more sustainable way, water electrolysers could be coupled with the well-developed photovoltaic solar cell technology to provide the energy input for green H2 production. Commercial PEM (proton exchange membranes) electrolysers operate in acidic pH which favours H2 production at the cost of using IrO2 as catalyst for oxygen production at the anode representing a significant drawback for this technology. Contrary, an AEM (anionic exchange membranes) operates in alkaline electrolytes which enables the use of low cost and highly active OER catalyst such as NiCoFeOx,1 however at the expense of including an extra overpotential to drive the H2 production in the electrolyser.2 Using bipolar membranes (BPM), where a cationic exchange membrane CEM is used alongside an anionic exchange membrane, allows the electrolyser to operate at different pHs: at the cathode in an acidic environment to favour H2 production, and alkaline for O2 production at the anode. However, a BPM induces a significant increase in resistance across the electrolyser.2 Recently, it has been demonstrated that by adding metal oxides as water dissociation catalysts, the electrolyser overpotential significantly decreased passing from 8 V to 2.2 V at 500 mA cm-2.3 This milestone in the field was accomplished by using two metal oxides with different point of zero charge (PZC) 3 and 11 for IrO2 and NiO respectively. Interestingly, a similar performance was observed when only TiO2 was used as water dissociation catalyst which PZC sits between IrO2 and NiO.4 Indeed demonstrating the necessity of better understanding of the physicochemical phenomena that governs water dissociation interfaces. Using TiO2 as water dissociation catalyst provides a suitable platform to understand how properties such as conductivity or different doping content affect water dissociation during H2 production in the electrolyser. Therefore, in this work modifications of TiO2 were investigated and its impact on the cell voltage when used between Nafion 212 and Sustainion membranes as CEM and AEM respectively, in a commercial 5 cm2 electrolyser at 60 ⁰C that operates only with DI water. To only benchmark the performance of the BPM, Pt and IrO2 were chosen as H2 and O2 catalysts respectively. References [1] ACS Catal. 9 (2019) 7–15 [2] ACS Energy Lett. 7 (2022) 3447–3457 [3] Science 369, (2020) 1099–1103 [4] Nat. Commun. 13 (2022) 1–10
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Loh, Adeline, Xiaohong Li, Soraya Sluijter, Paige Shirvanian, Qingxue Lai, and Yanyu Liang. "Design and Scale-Up of Zero-Gap AEM Water Electrolysers for Hydrogen Production." Hydrogen 4, no. 2 (2023): 257–71. http://dx.doi.org/10.3390/hydrogen4020018.
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The design of a 10 cm2 (3.4 cm by 3.4 cm) and a 100 cm2 (10 cm by 10 cm) anion exchange membrane (AEM) water electrolyser cell for hydrogen production are described. The AEM cells are based on a zero-gap configuration where the AEM is sandwiched between the anode and cathode so as to minimise voltage drop between the electrodes. Nonprecious nickel-based metal alloy and metal oxide catalysts were employed. Various experiments were carried out to understand the effects of operating parameters such as current densities, electrolyte concentrations, and testing regimes on the performance of both 10 cm2 and 100 cm2 AEM electrolyser cells. Increasing electrolyte concentration was seen to result in reductions in overpotentials which were proportional to current applied, whilst the use of catalysts improved performance consistently over the range of current densities tested. Extended galvanostatic and intermittent tests were demonstrated on both 10 cm2 and 100 cm2 cells, with higher voltage efficiencies achieved with the use of electrocatalysts. Stability tests in the 100 cm2 AEM electrolyser cell assembled with catalyst-coated electrodes demonstrated that the cell voltages remained stable at 2.03 V and 2.17 V during 72 h operation in 4 M KOH and 1 M KOH electrolyte, respectively, at a current density of 0.3 A cm−2 at 323 K. The inclusion of cycling load tests in testing protocols is emphasized for rational evaluation of cell performance as this was observed to speed up the rate of degradation mechanisms such as membrane degradation.
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Malone, Iain, Seçil Ünsal, Thomas Samuel Miller, and Alex Rettie. "Investigating the Effect of KOH Feed Concentration on a Stainless-Steel Anode Using a 3-Electrode Anion Exchange Water Electrolyser Cell Set-up." ECS Meeting Abstracts MA2024-01, no. 34 (2024): 1824. http://dx.doi.org/10.1149/ma2024-01341824mtgabs.
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Anion-exchange membrane water electrolysers (AEM-WE) have the potential to lower the capital cost of hydrogen production compared to proton-exchange membranes water electrolysers (PEM-WE). The alkaline conditions of AEM-WE result in: (i) a kinetically more favourable oxygen evolution reaction (OER), (ii) the ability to use platinum group metal (PGM)-free metal catalysts, and (iii) reduced cell component costs because of the less corrosive operating conditions. However, AEM-WE is held back from commercialisation by limited current density and durability.1 Compared to conventional alkaline water electrolysis, AEM-WEs have the advantage of lower ohmic resistance thanks to a solid polymer electrolyte which provides intrinsic ionic conductivity instead of relying on 6 M KOH and a porous separator. Most studies show, however, that a dilute KOH feed (< 1 M), rather than pure water, is critical to reaching a high current density in AEM-WE. Varying the concentration of KOH in the feed solution impacts catalyst activity and membrane resistance thereby making performance measurements in AEM-WE more complex. Moreover, the overpotential for the alkaline hydrogen evolution reaction (HER) is significant due to its sluggish kinetics. This means full-cell measurements are insufficient for understanding the behaviour of OER and HER catalysts in AEM-WE. It is therefore crucial to make half-cell measurements in AEM-WEs to decouple the effect of the anode and cathode electrocatalysts from the overall cell performance. In this context, our group recently demonstrated a 3-electrode, 5 cm2 membrane electrode assembly electrolyser cell2 that uses a reference electrode to decouple the anode and cathode contributions to the overall water splitting reaction. The technique was demonstrated for AEM-WEs and is soon to be published by Malone et al. (Figure 1A)3. In this study, we aimed to investigate the effect of KOH concentration in the feed solution on OER by using this 3-electrode cell setup. We used a stainless steel (SS)-felt at the anode as both catalyst and porous transport layer (PTL) in different concentrations of KOH feed while maintaining Pt/C as the cathode catalyst. We also repeated the tests with various anode catalyst layers (IrOx, NiFeOx) in combination with the SS PTL. For each test, full and half-cell polarisation curves and impedance spectroscopy were recorded before and after a sixteen-hour durability test at 1 A cm-2 at 40 °C. The results revealed the catalytic significance of the SS-felt in 1 M KOH as recently shown by Chen et al.4 Additionally, we demonstrated how the SS masks the performance of an IrOx catalyst layer in 1 M KOH. Reducing the KOH concentration to 0.18 M resulted in ≈ 7 % increase in the overall cell voltage at 1 A cm-2 (from 1.88 V to 2.00 V at 40 °C in Figure 1B). Aside from the ≈ 35 % increase in membrane resistance (e.g. 180 to 240 mΩ cm2 at 0.9 A cm-2) in 0.18 M KOH, the higher overpotential arose from the anode (Figure 1C), which could be attributed to the higher OER overpotential of SS-felt in a lower pH solution. Meanwhile, there was no appreciable change in cathode overpotential when the KOH concentration was reduced. These findings demonstrate the importance of 3-electrode cell measurements for understanding the impact of each component in an AEM-WE cell. Furthermore, the results reveal that both the choice of PTL material as well as the concentration of feed solution should be considered when testing different catalysts in AEM-WE. References: Santoro, A. Lavacchi, P. Mustarelli, V. Di Noto, L. Elbaz, D. R. Dekel and F. Jaouen, ChemSusChem, 2022, 15, e202200027. J. Dodwell, M. Maier, J. Majasan, R. Jervis, L. Castanheira, P. Shearing, G. Hinds and D. J. L. Brett, J. Power Sources, 2021, 498, 229937. I. A. F. Malone, C. M. Zalitis, D. J. L. Brett, H. G. C. Hamilton and A. J. E. Rettie, 2023, (in preparation). B. Chen, A. L. G. Biancolli, C. L. Radford and S. Holdcroft, ACS Energy Lett., 2023, 8, 2661. Figure 1
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Wilke, Vincent, Marco Rivera, Aldo Saul Gago, and K. Andreas Friedrich. "Atmospherically Plasma-Sprayed Macro Porous Layers for Anion Exchange Membrane Water Electrolysis Operating with Alkaline Supporting Electrolyte." ECS Meeting Abstracts MA2024-02, no. 45 (2024): 3151. https://doi.org/10.1149/ma2024-02453151mtgabs.
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Green hydrogen produced via water electrolysis plays an important role in the decarbonisation of the global energy economy. Besides reducing electricity prices and increasing electrolyser efficiency, lowering electrolyser investment cost is an important avenue to make electrolysis technology more economically attractive. Anion exchange membrane water electrolysis (AEMWE) combines the advantages of proton exchange membrane water electrolysis (PEMWE), i.e., high current density while maintaining high efficiency and fast dynamic response with the advantages of alkaline water electrolysis (AWE), i.e., low-cost materials. However, an optimised porous transport layer (PTL) component for AEMWE is yet to be developed. Typically, PTLs in commercial electrolysers are metallic foams, felts, meshes, sintered sheets or graphitic fibre laminates, although these structures either perform poorly or they are extremely expensive. Furthermore, a high number of low-resistance contact points at the interface between the catalyst layer and the PTL is required to enable high catalyst utilisation. At the same time, operation at high current densities requires an especially efficient liquid/gas exchange at this interface. Both important functions, good electrical contact and mass transport facilitation, are fulfilled by a macro porous layer (MPL). Stiber et al designed and characterized a titanium/niobium MPL deposited via vacuum plasma spraying (VPS) on a stainless-steel mesh substrate, vastly improving the performance of a PEMWE [1]. Similarly, Razmjooei et al deposited a nickel layer via atmospheric plasma spraying (APS) and demonstrated the performance-increasing effect in AEMWE operating with pure water [2]. In this work, within the frame of the German project AEM-Direkt, a Ni-based MPL was developed to improve high current density operation in AEMWE working with a supporting alkaline electrolyte. For this, a Ni-C composite powder was deposited on a stainless-steel multi-mesh PTL via APS (Fig. a). The carbon acts as a pore forming agent and is subsequently removed by an ex-situ oxidation step in air at 700°C followed by a reduction step in ammonia at 500°C. A highly porous, smooth and flat Ni-MPL is formed. Using the MPL on the anode, the AEMWE single cell achieves 2 V at 3 A cm-2 (Fig. b), which is comparable to the performance of PEMWE. As anode catalyst layer a novel 20 nm thickness sputtered nickel layer designed and manufactured by Siemens-Energy was used, deposited on a DURAION® AEM, manufactured by Evonik Operations GmbH. As cathode, a Pt/C based catalyst coated substrate (CCS) was employed. In continuation of this study, the designed MPL will be further optimised and characterised as cathode MPL as well. Acknowledgement This work is carried out within the project AEM-Direkt (Förderkennzeichen 03HY130) funded by the German Ministry of Science and Education (BMBF). References Stiber S, Sata N, Morawietz T, Ansar SA, Jahnke T, Lee JK, et al. A high-performance, durable and low-cost proton exchange membrane electrolyser with stainless steel components. Energy & Environmental Science. 2022;15(1):109-22. Razmjooei F, Morawietz T, Taghizadeh E, Hadjixenophontos E, Mues L, Gerle M, et al. Increasing the performance of an anion-exchange membrane electrolyzer operating in pure water with a nickel-based microporous layer. Joule. 2021;5(7):1776-99. Figure 1
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Kaufmann, Bastian, Miriam Hesse, Moritz Pilaski, et al. "Anode Catalyst Layers for AEM-WE: Implementation, Characterisation and Evaluation of Different Synthesis Routes." ECS Meeting Abstracts MA2024-02, no. 45 (2024): 3150. https://doi.org/10.1149/ma2024-02453150mtgabs.
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The global energy sector's transformation and requisite technological shifts present an unprecedented challenge for politics, industry, and research. Green hydrogen, produced through water electrolysis, is pivotal for storing fluctuating renewable electricity and decarbonizing power demanding industries (e.g. steel production). Current electrolysis technologies do not achieve high efficiencies or require critical materials such as iridium, titanium or flourinated polymers. For these reasons, alkaline electrolyte membrane water electrolysis (AEM-WE) has garnered increased attention from industry and research in recent years. The technology involves many construction principles and advantages of the PEM-WE without its disadvantages. However, further research is necessary to understand electrochemical interactions and technical implementation, especially in catalyst-related topics. In this work, therefore different types of catalyst layers are prepared and characterized. Depending on the catalyst type distinct preparation methods are applied and the resulting layers are evaluated electrochemically. Full cell experiments are conducted with combined membrane electrode assemblies and in conjunction with electrochemical impedance spectroscopy are used to provide information on contact resistance, electrochemical surface area and overall mass activity. The applied catalytic materials are made by galvanic deposition, corrosion, precipitation and physical vapour deposition of active species on support materials. Based on the employed preparation method the catalyst implementation and subsequent utilization varies. In particular catalysts from precipitation and PVD-coating were studied in terms of deposition configurations, catalyst loading and a comparison to more widespread catalyst systems. Due to the increase of the specific active surface area by the shape of the synthesised core-shell-like particles, even small amounts of active species could be implemented in highly active layers and thus enable high current densities in optimised electrolysers. Figure 1
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Bashiri, Shaghayegh, Zhiqiao Zeng, Leonard J. Bonville, Stoyan Bliznakov, and Radenka Maric. "Comparative Study of Anion Exchange Membranes for Application in Advanced AEM Water Electrolysers." ECS Meeting Abstracts MA2024-01, no. 34 (2024): 1739. http://dx.doi.org/10.1149/ma2024-01341739mtgabs.
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The chemical nature of hydrogen combined with its capability to be an energy carrier for energy conversion devices with zero- emission and its higher energy density than any other commercial fossil fuel-based energy source, make it unique [1]. The International Renewable Energy Agency has identified three of the most viable technologies for producing hydrogen in large volume, namely: alkaline water electrolyzers (AWEs), proton exchange membrane water electrolyzers (PEMWEs), and anion exchange membrane water electrolyzers (AEMWEs) [2]. Among the three types of electrochemical devices the AEMWEs are the newest and most promising, because they (i) have the same slim design of the PEMWEs, (ii) can operate at high current densities, and (iii) can use non-precious catalysts [3]. The durability and efficiency of the AEMWEs systems are significantly influenced by the anion exchange membranes (AEMs), which are currently under development. In addition, the used catalysts, as well as the methods for fabrication of the membrane electrode assemblies (MEAs) also impact substantially the electrolyzer’s performance. Catalyst-coated substrate (CCS) is one of the methods for fabrication of MEAs [4], while the other used method is known as catalyst coated membranes (CCMs). The Reactive Spray Deposition Technology (RSDT) is an innovative flame-assisted method that can be used for fabrication MEAs from both types [5]. In this work, CCS are fabricated by the ultrasonic spray deposition method and 5 MEAs are assembled with various AEM membranes. This approach involves the application of Platinum Group Metal (PGM) catalysts, Pt/C and as cathode and anode catalyst layers, onto a Gas Diffusion Layer (C-GDL) and a porous transport layer (Ti-PTL). As fabricated CCSs are assembled with the three state-of-the-art commercially available AEMs, namely: FAA-3, Sustainion X-37, and TM1, and their performance is evaluated. In addition, CCSs with ultra-low PGM loadings in their catalyst layers are fabricated with the RSDT method and better performance in comparison to the baseline MEAs with high PGM loadings, is achieved. This comparative study provides valuable insights into the strengths and weaknesses of each membrane type for application in AEM water electrolysers. Reference: [1] M. G. Rasul, M. A. Hazrat, M. A. Sattar, M. I. Jahirul, and M. J. Shearer, “The future of hydrogen: Challenges on production, storage and applications,” Energy Conversion and Management, vol. 272, p. 116326, Nov. 2022, doi: 10.1016/j.enconman.2022.116326. [2] D. Yang et al., “Patent analysis on green hydrogen technology for future promising technologies,” International Journal of Hydrogen Energy, vol. 48, no. 83, pp. 32241–32260, Oct. 2023, doi: 10.1016/j.ijhydene.2023.04.317. [3] D. S. Falcão, “Green Hydrogen Production by Anion Exchange Membrane Water Electrolysis: Status and Future Perspectives,” Energies, vol. 16, no. 2, p. 943, Jan. 2023, doi: 10.3390/en16020943. [4] J. E. Park et al., “High-performance anion-exchange membrane water electrolysis,” Electrochimica Acta, vol. 295, pp. 99–106, Feb. 2019, doi: 10.1016/j.electacta.2018.10.143. [5] Z. Zeng, J. Xing, L. Bonville, D. R. Dekel, R. Maric, and S. Bliznakov, “Advanced nickel-based catalysts for the hydrogen oxidation reaction in alkaline media synthesized by reactive spray deposition technology: Study of the effect of particle size,” International Journal of Hydrogen Energy, p. S0360319923013721, Apr. 2023, doi: 10.1016/j.ijhydene.2023.03.249.
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Varcoe, John, Rachida Bance-Souahli, Arup Chakraborty, et al. "The Latest Developments in Radiation-Grafted Anion-Exchange Polymer Electrolytes for Low Temperature Electrochemical Systems." ECS Meeting Abstracts MA2022-01, no. 35 (2022): 1443. http://dx.doi.org/10.1149/ma2022-01351443mtgabs.
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Anion-exchange membranes (AEM) are being developed for use in electrochemical technologies including fuel cells (AEMFC),water electrolysis (AEMWE for green hydrogen), electrolysers for CO2 reduction (CO2RR), and reverse electrodialysis (RED). Radiation-grafted AEMs (RG-AEM) represent a promising class of AEM that can exhibit high conductivities (OH- conductivities of > 200 mS cm-1 at temperatures above 60 °C) and favourable in situ water transport characteristics). Hence, RG-AEMs have shown significant promise when tested in AEMFCs alongside powdered radiation-grafted anion-exchange ionomers (RG-AEI), producing high performances and promising durabilities [Energy Environ. Sci., 12, 1575 (2019) and Nature Commun., 11, 3561 (2020)], even at temperatures above 100 °C [Dekel et al., J. Power Sources Adv., 5, 100023 (2020)]. An Achilles heel with RG-AEM types is that they can swell excessively in water and have large dimensional changes between the dehydrated and hydrated states. This limits the ion-exchange capacities (IEC) that can be used: excessive IECs in RG-AEM will cause excessive swelling and poorer robustness. This clearly indicates that additional crosslinking is needed. As Kohl et al. have highlighted, optimised crosslinking can lead to production of high-IEC AEMs that are both robust enough to be < 20 µm in thickness and also low swelling [e.g. J. Electrochem. Soc., 166, F637 (2019)], allowing truly world-leading AEMFC performances. RG-AEMs are also being used as a screening platform for down-selecting different (cationic) head-group chemistries for use in RED cells (a salinity gradient power technology), where different head-groups may lead to different AEM characteristics such as: in-cell resistance (when in contact with aqueous electrolytes), permselectivity, and fouling characteristics (when real world waters such as industrial brines, seawater and freshwater are used). It was evident very early on in these studies that RG-AEMs (desirably) exhibit extremely low resistances but also (undesirably) very low permselectivities when un-crosslinked (less than the required 90%+ permselectivity). Our work on RG-type cation-exchange membranes [Sustainable Energy Fuels, 3, 1682 (2019)] clearly shows that introduction of crosslinking can improve permselectivity. Crosslinking always involves a compromise, where its introduction can improve a membrane characteristic (e.g. reduced swelling or improved permselectivity) but also leads to lower conductivities or poorer transport of chemical species through the membranes. Hence, crosslinking types and levels need to be carefully controlled. With RG-AEMs (made by electron-beam activation (peroxidation) of inert polymer films, followed by grafting of monomers and post-graft amination), we have a choice of introducing crosslinking at various stages. The figure below summarises the two different approaches to crosslinking that will be discussed in the presentation: adding a divinyl-type crosslinker into the grafting mixture or adding a diamine-type crosslinker into the amination step. This presentation will present a selection of recent RG-AEM and RG-AEI developments from a number of projects: (1) REDAEM: AEMs for RED cells [EPSRC Grant EP/R044163/1]; (2) CARAEM: Novel RG-AEMs for AEMFCs and AEMWE [EPSRC Grant EP/T009233/1]; (3) SELECTCO2: RG-AEMs being tested in CO2RR cells [EU Horizon 2020 grant agreement 851441]. This presentation will show: (a) RG-AEMs made from thin high density polyethylene (HDPE) precursors appear better for application in AEMFCs, while RG-AEMs from made from thicker ETFE precursors appear to be better for CO2RR cells and RED; (b) RG-AEMs can be made using a variety of crosslinking strategies; (c) RG-AEIs can be made using ETFE powders and give optimal performance after cryogrinding down to micrometer sizes; Figure 1
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Hasché, Frédéric, David Sauss, and Mehtap Oezaslan. "Hydrogen Terminal Braunschweig – a Research Demonstration Facility Along the Hydrogen Value Chain." ECS Meeting Abstracts MA2024-02, no. 50 (2024): 4985. https://doi.org/10.1149/ma2024-02504985mtgabs.
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Two of the greatest challenges in the energy transition are still the transportation and storage of renewable energy. For a green hydrogen economy, electrochemistry will play a major role. This project will show a comprehensive integration of various hydrogen technologies to an integrated physical network at megawatt scale. Our demonstration facility, namely Hydrogen Terminal Braunschweig, is located in Lower Saxony, Germany and was established in Summer 2024 [1]. In the Hydrogen Terminal Braunschweig, the green hydrogen (H2) is generated by the world's first commercially available 1 MW electrolyzer prototype of anion exchange membrane (AEM) technology [2]. The produced H2 from the renewable energy will be stored and used for a heavy-duty truck refilling station (350 bar) as well as transported to internal and external fuel cell test benches via pipelines. In addition to the H2 supply, one of the external consumption points is also fed with electrolysis “waste” heat. The waste heat from the 1 MW electrolyzer is collected, processed in a high-temperature heat pump and supplied via a local heating network. Moreover, the technical interplay and conjunction between electrolyzers and fuel cells with a large battery storage system (1.1 MWh storage capacity) and photovoltaic systems to stabilize the electrical grid will be investigated in detail. Here, a medium-voltage switchgear enables off-grid island operation as well as partial load and full load scenarios of all connected electrical components via switch positions. Last but not least, we will develop an education and training program for various target groups in the field of hydrogen technologies and energy transition in the near future. References [1] https://magazin.tu-braunschweig.de/en/pi-post/opening-and-open-day-of-the-hydrogen-terminal-braunschweig/, press releases, 21. June 2024 [2] https://www.enapter.com/aem-electrolysers/aem-nexus/, Aug 2024
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Ferriday, Thomas B., Suhas Nuggehalli Sampathkumar, Peter Middleton, Mohan Lal Kolhe, and Herle Jan Van. "A Review of Membrane Electrode Assemblies for the Anion Exchange Membrane Water Electrolyser: Perspective on Activity and Stability." International Journal of Energy Research 2024 (April 25, 2024): 7856850. https://doi.org/10.1155/2024/7856850.
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The performance of a water electrolyser (WE) depends on several aspects, many of which are located in the powerhouse of the cell, namely, the membrane electrode assembly (MEA). The anion exchange membrane WE (AEMWE) is a promising technology; however, both activity and stability must be further developed to surpass the current dominant WE technologies. Herein, we review aspects related to MEA development for anion exchange membrane water electrolysers, covering materials and techniques from the perspective of stability and activity. The gas diffusion layer (GDL) and the microporous layer (MPL) are often combined into a single MEA component, which places great importance on its composition. This composite layer has the greatest impact of any single component on cell performance, as the physical architecture of the GDL/MPL influences the overpotential related to activation, ohmic, and mass transport. The purpose of this review is to serve as an executive summary of the literature related to MEAs for AEMWEs for researchers and industry professionals who seek to further the state of the art.
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de Groot, Arend, Sara Fabrizio, Giulia Marcandali, et al. "(Invited) Looking Beyond the Stack: A Systems Engineering Approach to Optimize Stack and System Design of Electrolysers." ECS Meeting Abstracts MA2024-01, no. 34 (2024): 1865. http://dx.doi.org/10.1149/ma2024-01341865mtgabs.
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In the coming decade green hydrogen production is expected to grow at an unparalleled rate. Much of the international focus is currently on the Gigawatt scale plants, with regular announcement of new projects. From a European perspective, the rapid scale-up is necessary to reduce the reliance on fossil fuels and achieve CO₂ reduction targets. Importing green hydrogen or derivatives such as ammonia from regions where renewable electricity cost are low, is key driver for investments for the energy intensive industry, especially in the North Western part of Europe. This will require hydrogen production on a very large-scale. In contrast to the differentiation on application level, a one-size fits all approach for stack manufacturing appears to be attractive, with a high degree of standardisation and volume of production. However, as the case for the Netherlands illustrates, there are more drivers for green hydrogen production, such as addressing (regional) grid congestion, improving the business case for offshore wind farm developments, and providing green energy to small and medium enterprises. For all these use cases the requirements for the electrolyser system differ. Aspects such as the variability of the energy supply, capacity factors, logistics for operation and maintenance, available footprint, are application specific. Therefore, electrolyser system designs may need to be optimized for different markets and applications. At TNO we focus on the development, integration and validation of novel materials and innovative cell components for the different generations of electrolyser technology, both for low temperature (liquid alkaline, PEM, AEM) and high temperature electrolysers. To understand and assess the requirements for future generations of electrolyser technology, a systems engineering approach is developed together with the industrial partners. This allows to translate the requirements from the application, to the system and stack design, down to the requirements on a cell and component level. Results will be presented from several studies carried out by TNO and industrial partners in the field of low temperature electrolyser systems to understand: How to optimize a stack design for a specific application. Should an electrolyser be designed to maximize flexible operation and achieve a broad operating range? Or will a high efficiency be the most important target? And how application specific is such an optimisation. How to bring down the cost of the total system. What impact do the design choices for the electrolyser stack have on the complexity of the system around the electrolyser, the balance-of-plant? What can we learn from this for the future stack requirements? How different operating strategies impact a certain design. Which stack requirements change in large multi-stack systems powered by renewable electricity supply? Can different strategies improve overall system performance and bring down the overall cost of hydrogen production? How can the desired safety level be achieved against the lowest cost by optimizing component and stack design? As both the electrolyser technology and the value chains become more mature, a systems engineering approach will be indispensable, bringing together the requirements of the different levels: from application, electrolyser system and stack design, down to the performance of individual components.
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Faour, Maisa, Karam Yassin, and Dario R. Dekel. "Anion-Exchange Membrane Oxygen Separator." ACS Organic & Inorganic Au 4, no. 5 (2024): 498–503. https://doi.org/10.1021/acsorginorgau.4c00052.
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Anion-exchange membranes (AEMs), known for enabling the high conductivity of hydroxide anions through dense polymeric structures, are pivotal components in fuel cells, electrolyzers, and other important electrochemical systems. This paper unveils an unprecedented utilization of AEMs in an electrochemical oxygen separation process, a new technology able to generate enriched oxygen from an O<sub>2</sub>/N<sub>2</sub> mixture using a small voltage input. We demonstrate a first-of-its-kind AEM-based electrochemical device that operates under mild conditions, is free of liquid electrolytes or sweep gases, and produces oxygen of over 96% purity. Additionally, we develop and apply a one-dimensional time-dependent and isothermal model, which accurately captures the unique operational dynamics of our device, demonstrates good agreement with the experimental data, and allows us to explore the device’s potential capabilities. This novel technology has far-reaching applications in many industrial processes, medical oxygen therapy, and other diverse fields while reducing operational complexity and environmental impact, thereby paving the way for sustainable on-site oxygen generation.
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Gerhardt, Michael Robert, Alejandro O. Barnett, Thulile Khoza, et al. "An Open-Source Continuum Model for Anion-Exchange Membrane Water Electrolysis." ECS Meeting Abstracts MA2023-01, no. 36 (2023): 2002. http://dx.doi.org/10.1149/ma2023-01362002mtgabs.
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Anion-exchange membrane (AEM) electrolysis has the potential to produce green hydrogen at low cost by combining the advantages of conventional alkaline electrolysis and proton-exchange membrane electrolysis. The alkaline environment in AEM electrolysis enables the use of less expensive catalysts such as nickel, whereas the use of a solid polymer electrolyte enables differential pressure operation. Recent advancements in AEM performance and lifetime have spurred interest in AEM electrolysis, but many open research areas remain, such as understanding the impacts of water transport in the membrane and salt content in the electrolyte on cell performance and degradation. Furthermore, integrating electrolyser systems into renewable energy grids necessitates dynamic operation of the electrolyser cell, which introduces additional challenges. Computational modelling of AEM electrolysis is ideally suited to tackle many of these open questions by providing insight into the transport processes and electrochemical reactions occurring in the cell under dynamic conditions. In this work, an open-source, transient continuum modelling framework for anion-exchange membrane (AEM) electrolysis is presented and applied to study electrolyzer cell dynamic performance. The one-dimensional cell model contains coupled equations for multiphase flow in the porous transport layers, a parameterized solution property model for potassium hydroxide electrolytes, and coupled ion and water transport equations to account for water activity gradients within the AEM. The model is validated with experimental results from an AEM electrolyser cell. We find that pH gradients develop within the electrolyte due to the production and consumption of hydroxide, which can lead to voltage losses and cell degradation. The influence of these pH gradients on potential catalyst dissolution mechanisms is explored and discussed. Finally, initial studies of transient operation will be presented. This work has been performed in the frame of the CHANNEL project. This project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking (now Clean Hydrogen Partnership) under grant agreement No 875088. This Joint undertaking receives support from the European Union's Horizon 2020 Research and Innovation program, Hydrogen Europe and Hydrogen Europe Research. Some of this work has been performed within the MODELYS project "Electrolyzer 2030 – Cell and stack designs" financially supported by the Research Council of Norway under project number 326809.
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Ferriday, Thomas, Suhas Nuggehalli Sampathkumar, Peter Hugh Middleton, and Jan Van herle. "(Digital Presentation) Quantifying the Effect of Potential Cycling Conditions on the Resulting Performance of Stainless Steel as an Anode for Alkaline Water Electrolysis." ECS Meeting Abstracts MA2023-01, no. 36 (2023): 2121. http://dx.doi.org/10.1149/ma2023-01362121mtgabs.
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Alkaline water electrolysis through the use of the anion exchange membrane (AEM) has great potential. The current industry standard for water electrolysis utilise diaphragm-based traditional alkaline water electrolysers (AWEs), however using AEM water electrolysers (AEMWEs) introduces benefits including greater current densities, superior hydrogen purity, simpler cell/stack designs and less corrosive electrolytes. These advantages are additions to the pre-existing benefits to AWE, namely the possibility of utilising inexpensive catalyst materials for both hydrogen and oxygen evolution. Great attention has been payed to stainless steel (SS) as an anode for AEMWE due to its fair activity, low cost and good stability. Potential cycling (PC) is one method of electrochemically modifying the surface of various SS structures to increase electrochemical activity, however the PC conditions thus far reported in literature are rife with variation. As such, the full extent of PC conditions on SS remain unreported. Herein, we seek to fill this gap in literature by potential cycling a series of SS felt (SSF) electrodes under varied scan rates and ranges. Special attention is payed to surface conditions due to the intricate nuances affecting the electrocatalytic activity of the surface oxide layer. Two redox couples are clearly visible in cyclic voltammetry (CV) in the range 0-1.90 VRHE, termed whole-range, namely the Fe+2/Fe+3 at 0-0.65 VRHE and Ni+2/Ni+3 at 1.50-1.75 VRHE. The SSF electrodes were PC over one of these ranges at either slow, intermediate or fast scan rates, producing six different SSF electrodes. Initiating measurements were carried out to ascertain the baseline performance, including whole-range CV, electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV). The pristine SSF surface was exceedingly sensitive to the whole-range CV sweeps during initial measurements. Thus, this work is divided between SSF electrodes with and without CV in the initial measurements, termed with and without pre-cycling. Without pre-cycling, the decline in charge transfer resistance (Rct) before and after PC was more than tenfold for all scan speeds. Scan speed was relevant, where slow and fast scan speeds resulted in a mean Rct reduction of 84.15 and 90.59% for fast and slow scan speeds respectively. Post-experimental surface analysis with X-ray photoelectron spectroscopy revealed a decline in the average oxidation state of the principle elements in the SSF electrodes (Fe, Ni and Cr) and a surface depletion of iron. The relative increase in surface concentration of nickel and chromium was highly correlated with the reduction of Rct. Evaluation of affiliated Tafel slopes and LSV curves reveals similar trends, where the latter indicates a fair performance increment between 8-21% for fast and slow scan speeds. With pre-cycling the decline in Rct was lower, in the range of 18-30% and 3-7% for the SSF electrodes cycled around the Fe+2/Fe+3 and Ni+2/Ni+3 redox couple respectively. The influence of scan rate was the same for these SSF electrodes as with those unexposed to pre-cycling. Tafel analysis reveals two dominant slopes, where PC elicits small changes in the low current density slope and greater changes in the high current density region for the Fe+2/Fe+3 cycled SSF electrodes. These trends are also seen in LSV curves, where the greatest improvement is clearly seen for the SSF electrode cycled with a slow scan rate. Tafel analysis shows that the SSF electrodes cycled around the Ni+2/Ni+3 redox couple display a small decline in kinetics following PC, which corresponds to the rather meagre improvement in Rct affiliated with the PC conditions. The same trends are also seen by comparing the before and after LSV curves. Additional measurements documenting the full cell performance of these anodes is necessary and will be featured in the unabridged version of this paper, in addition to a more thorough characterisation of the surface conditions.
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Carroll, Zachary Liam, Michel Haché, Bowen Wang, et al. "Electrodeposition of Non-Noble High-Entropy Alloys for Effective Hydrogen Evolution Electrocatalysts." ECS Meeting Abstracts MA2024-01, no. 34 (2024): 1874. http://dx.doi.org/10.1149/ma2024-01341874mtgabs.
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As society works towards reducing its carbon footprint, various sectors such as energy, steelmaking and fertilizer production have begun to look increasingly towards decarbonization. Hydrogen production through electrolysis, when linked to renewables (solar, wind), provides a promising low-emission alternative as an energy carrier and chemical feedstock. With the decreasing cost of said renewables, greater focus is now on the capital cost of the electrolyser, and particularly the membrane/electrode structures. Conventional Proton Exchange Membrane (PEM) electrolysers rely on the use of electrocatalysts made with expensive noble metals such as platinum, ruthenium, and palladium [1]. Anion Exchange Membrane (AEM) electrolysers present an effective means of alkaline water splitting with low carbon emissions and can effectively utilize non-noble metal electrocatalysts for the Hydrogen Evolution Reaction (HER). A novel class of materials, High-Entropy Alloys (HEAs), made of non-noble metals or with reduced noble metal content have shown great promise as active electrocatalytic materials [2]. HEAs are typically defined as metal alloys made of five or more constituent elements each comprising at least 5% of the total material [3]. Having such a large number of principal alloying elements can lead to enhanced phase stability due to an increased configurational entropy, have unique chemical clustering, and can help prevent degradation of the material in harsh environments [2]. Additionally, the large lattice parameter mismatch between constituent elements can result in a high degree of strain which can help shift electronic states in a way that is favourable to hydrogen electrocatalysis [4]. These properties along with the so called “cocktail effect,” whereby combining multiple elements can result in unexpected synergistic interactions, makes HEAs uniquely suited to electrocatalytic applications [5]. In this work, we investigate the electrocatalytic performance of electrodeposited FeNiCoMoW HEAs. The goal is to combine three hyper-d transition metals with two hypo-d transition metals to alter the electronic structure and improve electrocatalytic performance. Using chronoamperometric measurements, the Tafel slopes for FeNiCoMoW HEAs electrodeposited at pH 5, 6 and 7 were determined, with the pH 5 HEA demonstrating the smallest average Tafel slope of approximately 83 mV/dec. Compared to some electrodeposited binary alloys reported on in the literature, this marks an improvement and may be the result of unexpected interactions within the compositionally complex alloy. In the FeNiCoMoW HEA, the magnitude of the Tafel slope increased in tandem with the electrochemically active surface area (ECSA) as determined by Cyclic Voltammetry (CV) which suggests that the composition may be more important for improving performance. As the pH of the electrodeposition solution increased, the amount of cobalt in the as-deposited HEA decreased while the amounts of molybdenum and tungsten remained constant. The composition of nickel and iron appeared to vary inversely, reaching a maximum and minimum respectively at pH 6. From these results it seems that maximizing cobalt content and minimizing nickel content could potentially help to improve HER performance in the FeNiCoMoW system. References: [1] J. Song et al., “Implementation of Proton Exchange Membrane Water Electrolyzer with Ultralow Pt Loading Cathode through Pt Particle Size Control,” ACS Sustain. Chem. Eng., vol. 11, no. 45, pp. 16258–16266, Nov. 2023, doi: 10.1021/acssuschemeng.3c04679. [2] G. M. Tomboc, T. Kwon, J. Joo, and K. Lee, “High entropy alloy electrocatalysts: a critical assessment of fabrication and performance,” J. Mater. Chem. A, vol. 8, no. 30, pp. 14844–14862, Aug. 2020, doi: 10.1039/D0TA05176D. [3] J.-W. Yeh et al., “Nanostructured High-Entropy Alloys with Multiple Principal Elements: Novel Alloy Design Concepts and Outcomes,” Adv. Eng. Mater., vol. 6, no. 5, pp. 299–303, 2004, doi: 10.1002/adem.200300567. [4] T. Löffler et al., “Toward a Paradigm Shift in Electrocatalysis Using Complex Solid Solution Nanoparticles,” ACS Energy Lett., vol. 4, no. 5, pp. 1206–1214, May 2019, doi: 10.1021/acsenergylett.9b00531. [5] Y. Zhang, D. Wang, and S. Wang, “High-Entropy Alloys for Electrocatalysis: Design, Characterization, and Applications,” Small, vol. 18, no. 7, p. 2104339, 2022, doi: 10.1002/smll.202104339. Figure 1
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Kemppainen, Erno, Iris Dorbandt, Karuppasamy Dharmaraj, et al. "Electrochemical Impedance Analysis of Direct Ammonia Fuel Cell Operation and Clamping Effects." ECS Meeting Abstracts MA2023-02, no. 37 (2023): 1799. http://dx.doi.org/10.1149/ma2023-02371799mtgabs.
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In addition to being an essential chemical for fertilizers, ammonia can also be used as a hydrogen carrier or directly as a fuel. Compared to hydrogen, the main advantages are that ammonia can be liquefied in mild conditions and the technology for ammonia shipping and pipelines already exists. Compared to carbon-based synthetic fuels, no carbon dioxide is produced by the oxidation, only water and nitrogen. The theoretical voltage of a direct ammonia fuel cell (DAFC) is 1.17 V, nearly equal to the 1.23 V of hydrogen fuel cells (HFC) but a central drawback is the slow kinetics of the ammonia oxidation reaction (AOR). The AOR is even slower than the oxygen reduction reaction (ORR) at the cathode, which in turn is the main voltage loss component in HFCs. Consequently, due to the AOR kinetics, DAFCs typically require significantly higher platinum group metal (PGM) catalyst loadings than HFCs for the same power output. To improve the performance of our aqueous-feed DAFC, especially using non-PGM catalysts, we carried out comparisons of catalysts and anion exchange membranes (AEM), and supplemented the comparison of power, voltage, and current parameters with electrochemical impedance spectroscopy (EIS). Additionally, we also compared measurements in two different test cells to try to identify the cause of measurement repeatability issues that we had when using one of the cells. Initially, we assumed that the reproducibility of catalyst deposition (or lack of it) and AEM or catalyst degradation in the ammonia-containing electrolyte had caused our repeatability problems. However, following a preliminary analysis of measurement statistics, we consider problems with the cell itself a more likely cause. The maximum power of the cell depended almost inversely on the series resistance (R S, i.e., the high-frequency resistance/real-axis intercept of the EIS spectrum), and the current at given voltage varied more than the differences in the resistance alone could explain when most measurement parameters were not varied (e.g., ammonia and hydroxide concentrations, liquid and gas flow rates). The general inverse dependence on R S remained also when measuring the same electrodes in different cells, and the performance did not necessarily degrade over time so, clearly, degradation and differences between electrodes could not explain everything. When testing different screw torques and gaskets in our AEM electrolyser, we had noticed that the voltage differences were often high compared to the R S differences, and it is known that clamping torque can affect the operation of fuel cells and electrolysers significantly. Nevertheless, more detailed analysis is ongoing to determine possible other contributing factors, to optimize the use of the cell(s) in measurements, and to guide future work. This research was done under the TELEGRAM project. This project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under grant agreement No 101006941. The project started on the 1st of November 2020 with a duration of 42 months. The authors acknowledge support from the Federal Ministry of Education and Research in the framework of the project Catlab (03EW0015A). Figure 1
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Storimans, Emma Adriana, and Steven Thorpe. "Novel Ni-V-Y Electrocatalysts for Hydrogen Evolution Reaction." ECS Meeting Abstracts MA2022-02, no. 29 (2022): 2544. http://dx.doi.org/10.1149/ma2022-02292544mtgabs.
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Generation of renewable energy is improving globally, the ability to store generated energy remains an issue. A new class of water electrolysers that utilize anion exchange membranes (AEMs) are effective at converting water to hydrogen gas which can be used as fuel. Novel electrocatalysts are required for AEMs to be active, stable, and cost effective when used in AEM water electrolysers. Previously, S. Ghobrial investigated the Ni-Nb-Y alloy system as an electrocatalyst for the hydrogen evolution reaction, with Ni and Y components contributed to electrocatalytic activity [1]. Nb phase did not contribute to electrochemical activity and behaved only as a glass former. For the second-generation alloy, V replaced Nb to create a Ni-V-Y alloy. Thermodynamic modelling via FactSage was used to develop the amorphous alloy system. To create the amorphous alloys, a two-step ball milling process was used. Elemental powders were mechanically alloyed and amorphized under cryogenic conditions. The micron sized alloyed powder was size reduced to nanoparticles suitable for use as electrocatalysts via surfactant assisted high energy ball milling (SA-HEBM). Both micron powders and nanoparticles were structurally characterized using X-ray diffraction and SEM. The catalytic activity of the electrocatalysts were electrochemically characterized using steady state polarization to determine Tafel slopes and exchange current densities. A Ni-V-Y alloy was successfully produced via cryomilling and SA-HEBM. The combination of the NiVY amorphous phase + Ni3V + Ni5Y phases in the micron and nanopowders improved activity relative to the intermetallics alone via the spillover effect. The surfactant used in SA-HEBM is not completely removed by the current centrifugation process leading to lower-than-expected activity and marginal spillover enhancement in nanoparticles. With an improved cleaning process, it is predicted the nanoparticles will have higher activities than their micron powder counterparts. [1] - S. Ghobrial, Amorphous Ni-Nb-Y Alloys as Hydrogen Evolution Electrocatalysts, Toronto: University of Toronto, 2019.
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Periasamy, Arun Prakash, Rosemary Rupesinghe, Rebecca Nash, et al. "(Invited) The Latest Developments in Radiation-Grafted Anion-Exchange Membranes." ECS Meeting Abstracts MA2024-01, no. 34 (2024): 1738. http://dx.doi.org/10.1149/ma2024-01341738mtgabs.
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This invited lecture will discuss the latest developments in radiation-grafted anion-exchange membranes (RG-AEM) that are being developed for a wide range of electrochemical technologies including fuel cells, electrolysers, and reverse electrodialysis. This presentation will discuss the following key points: RG-AEMs can have very high conductivities and water diffusivities, however they generally have excessive water uptakes and degrees of swelling in water, as well as poor permselectivities when in contact with aqueous salt solutions. Crosslinking can reduce swelling and improve permselectivities, but this is at the expense of conductivity. The cationic headgroup chemistries can alter the water uptakes of the RG-AEMs, which can impact properties such as their alkali stability and permselectivity. Subtle changes in amination can lead to RG-AEMs with very different water contents and diffusivities. When fully hydrated, RG-AEMs in the alkali forms can have usefully high stabilities at temperatures above 60oC. RG-AEMs can be made with multiple chemical functionalities either via the co-grafting of more than one monomer or via amination using more than one amine reagent (see scheme below). Finally, the presentation will present some recent undergraduate project results that probe the homogeneity of grafting using a new titration technique. Figure 1
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Gado, Alanna M., Deniz Ipekçi, Stoyan Bliznakov, Leonard J. Bonville, Jeffrey McCutcheon, and Radenka Maric. "Investigation of the Performance and Durability of Reactive Spray Deposition Fabricated Electrodes on a Bifunctional Membrane for Alkaline Water Electrolysis and CO2 Reduction Reaction." ECS Meeting Abstracts MA2023-01, no. 38 (2023): 2250. http://dx.doi.org/10.1149/ma2023-01382250mtgabs.
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Alkaline water electrolysis (AWE) is a promising technology for carbon capture [1]. Anion exchange membrane water electrolyzers (AEMWEs) utilize low-cost, non-precious metal materials, providing an economically viable alternative to more expensive proton exchange membrane water electrolyzers (PEMWEs). While PEMWEs can operate at much higher current densities, they require noble metal catalysts and titanium components for the high potential environment anode [1]. The implementation of a bipolar membrane (BPM) will allow both HER and OER to occur under kinetically favorable conditions [2, 3] by combining both thin AEM and thin PEM layers within a single membrane. AEMs, PEMs, and BPMs have been tested in CO2RR electrolyzers [4]. The BPM may provide a pathway to combine the advantages of both AEMs and PEMs for CO2 reduction. Altering both the membrane and CCM is a focus in the research and development in CO2RR electrolyzers. Lee et al. [5] explored the use of a porous membrane for CO2 reduction. While work can be done to improve performance and crossover, the porous membrane provided excellent mechanical properties and good economic potential. There has been some work done on developing bifunctional membranes for water electrolysis and CO2 reduction [3, 6, 7]. Two key issues with operation of a CO2RR electrolyzer with a BPM is the reactant CO2 that is lost to the AEM and PEM membrane layer interface and the instability of the cell. Both issues contribute to a significant decrease in performance and faradaic efficiency in product conversion. Development of the BPM, both on the membrane’s fabrication and configuration, and electrode layers, needs to be explored to reach higher performances and longer lifespans. In this work, reactive spray deposition technology (RSDT) was used to fabricate electrodes on a UConn fabricated bipolar membrane. Testing of each configuration was conducted as both an AEM water electrolyzer and CO2RR electrolyzer. Polarization, electrochemical impedance spectroscopy, electrochemical equivalent circuits, and distribution of relaxation times were used to investigate cell performance and durability. References [1] B. Mayerhofer, D. McLaughlin, T. Bohm, M. Hegelheimer, D. Seeberger, and S. Thiele, “Bipolar membrane electrode assemblies for water electrolysis,” ACS applied energy materials, vol. 3, no. 10, pp. 9635–9644, 2020. [2] J. Xu, I. Amorim, Y. Li, J. Li, Z. Yu, B. Zhang, A. Araujo, N. Zhang, and L. Liu, “Stable overall water splitting in an asymmetric acid/alkaline electrolyzer comprising a bipolar membrane sandwiched by bifunctional cobalt-nickel phosphide nanowire electrodes,” Carbon Energy, vol. 2, no. 4, pp. 646–655, 2020. [3] Q. Lei, B. Wang, P. Wang, and S. Liu, “Hydrogen generation with acid/alkaline amphoteric water electrolysis,” Journal of Energy Chemistry, vol. 38, pp. 162–169, 2019. [13] W. H. Lee, K. Kim, C. Lim, Y. J. Ko, Y. J. Hwang, B. K. Min, U. Lee, and H. S. Oh, “New strategies for economically feasible CO2 electroreduction using a porous membrane in zero-gap configuration,” Journal of Materials Chemistry A, vol. 9, pp. 16169–16177, 8 2021 [4] D. A. Salvatore, C. M. Gabardo, A. Reyes, C. P. O’Brien, S. Holdcroft, P. Pintauro, B. Bahar, M. Hickner, C. Bae, D. Sinton, E. H. Sargent, and C. P. Berlinguette, “Designing anion exchange membranes forCO2 electrolysers,” Nature Energy, vol. 6, pp. 339–348, 4 202 [5] W. H. Lee, K. Kim, C. Lim, Y. J. Ko, Y. J. Hwang, B. K. Min, U. Lee, and H. S. Oh, “New strategies for economically feasible CO2 electroreduction using a porous membrane in zero-gap configuration,” Journal of Materials Chemistry A, vol. 9, pp. 16169–16177, 8 2021 [6] W. Li, Z. Yin, Z. Gao, G. Wang, Z. Li, F. Wei, X. Wei, H. Peng, X. Hu, L. Xiao, J. Lu, and L. Zhuang, “Bifunctional ionomers for efficient CO electrolysis of CO2 and pure water towards ethylene production at industrialscale current densities,” Nature Energy, 2022 [7] C. P. O’Brien, R. K. Miao, S. Liu, Y. Xu, G. Lee, A. Robb, J. E. Huang, K. Xie, K. Bertens, C. M. Gabardo, et al., “Single pass CO2 conversion exceeding 85% in the electrosynthesis of multicarbon products via local CO2 regeneration,” ACS Energy Letters, vol. 6, no. 8, pp. 2952–2959, 2021.
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Ferriday, T. B., P. H. Middleton, and M. L. Kolhe. "Determining the change in performance from replacing a separator with an anion exchange membrane for alkaline water electrolysis." Journal of Physics: Conference Series 2454, no. 1 (2023): 012003. http://dx.doi.org/10.1088/1742-6596/2454/1/012003.
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Abstract The emphasis on energy storage has caused renewed interest in alkaline water electrolysis (AWE), where the novel anion exchange membrane (AEM) has opened new pathways to further improve this mature technology. The comparison between the novel and the mature is most commonly performed on uneven grounds, as the ionic conductivity of the 30 wt.% (6.89 M) KOH electrolyte used in AWE is significantly greater than the 1.0 M employed in AEM water electrolysis. Through this paper, the performance of a zero-gap water electrolyser is systematically tested utilising either a separator or an AEM in a 1.0 M KOH electrolyte over several temperatures. Catalysed with only untreated nickel foam, the cell configuration with the AEM displayed predictably enough a notably lower series resistance and thereby a lower overpotential. However, the cell with the separator displayed better innate thermal stability, and showed stable results at 25°C, 40°C and 70°C. These findings exhibit the potential of additional R&D efforts in both separators and AEMs.
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Douglin, John C., Ramesh K. Singh, Ami C. Yang-Neyerlin, et al. "Elucidating the degradation mechanisms of Pt-free anode anion-exchange membrane fuel cells after durability testing." Journal of Materials Chemistry A 12 (March 28, 2024): 10435–48. https://doi.org/10.1039/D3TA07065D.
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The development of anion-exchange membrane fuel cells (AEMFCs) has recently accelerated due to synergistic improvements yielding highly conductive membranes, stable ionomers, and enhanced alkaline electrocatalysts. However, cell durability, especially under realistic conditions, still poses a major challenge. Herein, we employ low-loadings of Pt-free Pd-based catalysts in the anode of AEMFCs and elucidate potential degradation mechanisms impacting long-term performance under conditions analogous to the real-world (high current density, H<sub>2</sub>–air (albeit CO<sub>2</sub>-free), and intermittent operation). Our high-performing AEMFCs achieve impressive performance with power densities approaching 1 W cm<sup>−2</sup> and current densities up to 3.5 A cm<sup>−2</sup>. Over a 200 h period of continuous operation in H<sub>2</sub>–air at a current density of 600 mA cm<sup>−2</sup>, our model Pd/C–CeO<sub>2</sub> anode cell exhibits record stability (∼30 μV h<sup>−1</sup> degradation) compared to the literature and up to 6× better stability than our Pd/C and commercial Pt/C anode cells. Following an 8 h shutdown, the Pd/C–CeO<sub>2</sub> anode cell was restarted and continued for an additional 300 h with a higher degradation rate of ∼600 μV h<sup>−1</sup>. Thorough <em>in situ</em> evaluations and post-stability analyses provide insights into potential degradation mechanisms to be expected during extended operation under more realistic conditions and provide mitigation strategies to enable the widespread development of highly durable AEMFCs.
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You-Zhi Tang. "Is hydrogen a silver bullet in fighting climate change and recent trends in hydrogen technologies." Naturalis Scientias 02, no. 01 (2025): 407–28. https://doi.org/10.62252/nss.2025.1028.
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This review article is not intended to audience that is specialized in the research and development as well as deployment of hydrogen technologies. Rather, it is for those who are in the fields of commercialization, investment and applications of new technologies, working in areas relevant to climate change and energy policies, as well as those who have a general interest in hydrogen energy. While hydrogen holds a bright future in reducing carbon emission and mitigating climate change, it is only one of the valid means among an integrated and diverse set of solutions. As part of the current effort for energy transition, hydrogen offers zero emission provided that the electricity used for generating hydrogen is from green sources. In the domain of producing green hydrogen, alkaline electrolysis (AE) currently dominates industrial applications thanks to its lower costs and reasonable efficiency, while it is expected proton exchange membrane (PEM) will pick up pace from 2030. Anion exchange membrane (AEM) is relatively new and may hopefully combine some of the advantages of both AE and AEM. However, each technology has its niche based on the application‘s specific requirements, such as cost sensitivity, purity needs, and operational flexibility. Producing hydrogen from biomass, including waste materials, is an area of active research and development and several technologies have been explored or under development for harnessing hydrogen from such resources. Manufacturing and applying more efficient and powerful electrolysers at lower costs is the way to go. While storing and shipping hydrogen in containers with hydrogen in a compressed gaseous or cryogenic liquified form remain the primary ways, solid-state storage of hydrogen is getting more and more attention, with metal hydrides such as MgH2, TiFeH₂, NaAlH₄, etc. getting close to full commercial applications. Dissolving hydrogen in organic solvents or converting it into ammonia, is a direction of on-going research. With a proper way for safe and low-cost storage of hydrogen in large scale, hydrogen as an energy carrier is a great candidate for grid balance. Although hydrogen can be used as a fuel directly such as with an internal combustion engine (ICE) or gas turbine, as well as used as a chemical reagent such as a reductant in steel making or as feedstock in a variety of industrial processes, a lot of attentions is paid to the use of hydrogen with fuel cells (FC). Current focuses on FC are reducing costs, adapting to harsher working conditions, enhancing flexibility and durability, increasing fuel types, finding more applications and scaling up. It is expected that the hydrogen industry will continue to attract large capital inflows in 2025 and beyond to achieve a low-carbon transition for energy-intensive sectors. Hydrogen infrastructures are being developed all over the world, with China seemingly leading the way. Transporting hydrogen by pipeline is important for developing a hydrogen economy, and demonstration projects are currently underway in many countries.
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Padgett, Elliot, Alex Badgett, Joe Brauch, et al. "(Invited) Comparing and Contrasting the Advantages and Challenges of Catalysts for Low Temperature AEM, AEL, and PEM Electrolysis." ECS Meeting Abstracts MA2024-01, no. 34 (2024): 1776. http://dx.doi.org/10.1149/ma2024-01341776mtgabs.
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Electrolysis has been promoted as a critical route to enabling green hydrogen and a broader US Department of Energy supported H2@Scale vision enabling a clean, economic and sustainable energy system.1 Low temperature electrolysis offers advantages over high temperature electrolysis in high temperature materials challenges, limited intermittency capabilities, thermal integration, lower manufacturing and technology readiness, steam conversion and separation challenges.2 Within low temperature electrolysis anion exchange membrane (AEM), (liquid) alkaline (AEL) and proton exchange membrane (PEM) electrolysis are the three primary electrolysis technologies being investigated. These electrolysis environments are different and the catalyst materials they employ, and the cost, natural abundance, performance, and durability limitations are all different. These factors have a significant impact on the research focus and needs for each of these competing technologies. This presentation will explore catalysis in each one of these systems and compare critical limitations of each. The PEM system depends on Ir for anode (OER) catalysis. Ir is expensive and one of the least abundant elements in the earth’s crust. While earth abundance of Ir may is a potential concern for projections of electrolysis needs,3,4 the ability to thrift Ir more efficiently and achieve improved durability are critical for achieving hydrogen cost targets. Specific features impacting the cost, performance and durability trade-offs of Ir in PEM electrolysis will be discussed in terms of hydrogen levelized costs and the research advances necessary to have a positive impact on PEM electrolyzers. AEM and AEL electrolysis are distinct in terms of the concentration of supporting (KOH) electrolytes being investigated and the types of electrodes typically employed. AEM electrolyzers typically work at 1M KOH concentrations or below and employ thin film electrodes with alkaline ionomer as a parallel to most PEM designs. AEL electrolyzers typically operate at high (30 wt% KOH) concentrations and consist of electrodes deposited onto metal substrates rather than deposited as a thin film onto the membrane/separator. The materials sets and some of the performance and durability challenges of each of these systems are similar. They also have challenges at both the anode and cathode, where as PEM cathodes operate highly efficiently and durably with low loadings of Pt. The primary advantage of alkaline systems is the ability to enable highly earth abundant electrocatalysis, but challenges remain for performance and durability tradeoffs. These aspects as well as their implications for hydrogen levelized cost will be presented along with target research needs. https://www.energy.gov/eere/fuelcells/h2scale. Alex Badgett, Mark Ruth, Bryan Pivovar, “Economic considerations for hydrogen production with a focus on polymer electrolyte membrane electrolysis,” Electrochemical Power Sources: Fundamentals, Systems, and Applications, 2022, 327-364. Cortney Mittelsteadt, Esben Sorensen, and Qingying Jia, Ir Strangelove, or How to Learn to Stop Worrying and Love the PEM Water Electrolysis Energy Fuels 2023, 37, 17, 12558–12569. Mark Clapp, Christopher M. Zalitis, Margery Ryan, Perspectives on current and future iridium demand and iridium oxide catalysts for PEM water electrolysis, Catalysis Today 420 (2023) 114140.
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Luong, Triet Nguyen Dai, Si Chen, and Patric Jannasch. "Hydroxide Conducting Naphthalene-Containing Polymers and Membranes Via Polyhydroxyalkylations." ECS Meeting Abstracts MA2023-02, no. 39 (2023): 1890. http://dx.doi.org/10.1149/ma2023-02391890mtgabs.
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Anion exchange membranes (AEMs) are critical components of alkaline membrane water electrolyzers and fuel cells that are under development today [1,2]. Consequently, there is a strong demand for highly conductive and alkali-stable AEMs. In this context, polyhydroxyalkylation has emerged as one of the most efficient synthetic pathways to chemically resistant polymer backbones for AEMs. In these Friedel-Crafts type polycondensations, an electron-rich aromatic compound reacts with an activated ketone or aldehyde to produce an aryl-ether-free polymer. The desired quaternary ammonium cations are then usually introduced through a Menshutkin reaction [3,4]. In the current work, we have employed naphthalene-based compounds as monomers in polyhydroxyalkylations to prepare a series of high-molecular weight poly(naphthalene alkylene)s with various naphthalene contents. These polymers were then quaternized and cast into AEMs. Here, we will discuss the influence of the naphthalene monomer type and content on AEM properties such as solubility, water uptake, ion conductivity, ionic clustering, thermal and alkaline stability, and also the prospects of using these AEMs in electrochemical systems. References: [1] Chen, N., Wang, H.H., Kim, S.P. et al. Poly(fluorenyl aryl piperidinium) membranes and ionomers for anion exchange membrane fuel cells. Nat. Commun. 12, 2367 (2021). [2] Li, D., Park, E.J., Zhu, W. et al. Highly quaternized polystyrene ionomers for high performance anion exchange membrane water electrolysers. Nat. Energy 5, 378–385 (2020). [3] Olsson, J.S., Pham, T.H., Jannasch, P., Poly(arylene piperidinium) hydroxide ion exchange membranes: synthesis, alkaline stability, and conductivity. Adv. Funct. Mater. 28, 1702758 (2017). [4] Pan, D., Bakvand, P.M., Pham, T.H., Jannasch, P. Improving poly(arylene piperidinium) anion exchange membranes by monomer design. J. Mater. Chem. A 10, 16478–16489 (2022).
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Lemcke, Michelle Sophie, Wolfram Münchgesang, Nadine Menzel, and Michael Bron. "Influence of Contact Pressure and Flow Rate on the Performance of Anion Exchange Membrane Electrolysis." ECS Meeting Abstracts MA2023-02, no. 38 (2023): 1822. http://dx.doi.org/10.1149/ma2023-02381822mtgabs.
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Hydrogen production by electrolysis is a key aspect of a climate-neutral economy. However, there are still weak points in the established low-temperature technologies such as high material costs in case of PEM electrolysis and poor dynamic operations in case of alkaline electrolysis. The emerging electrolysis technology, the anion exchange membrane (AEM) electrolysis, addresses these weaknesses and combines their advantages. Due to the solid polymer electrolyte and the alkaline environment, AEM water electrolysis is featured by a compact zero-gap cell design and inexpensive materials like non-noble metal catalysts. Hence, it offers the potential to a cost-effective and efficient electrolysis technology. To enable the breakthrough of this technology, we contribute by conducting performance evaluations of membrane electrode assemblies (MEAs) under application-oriented conditions. One focus is on non-noble metal MEAs with an active area of 25 cm2 operated with pure water and low concentrated potassium hydroxide solution. To ensure comparability of different MEAs, it is crucial to compare them at their performance optimum. This is achieved by determining the optimal set-up parameters like contact pressure and operation parameters like flow rate for each MEA type. Otherwise, deviation from the optimal operating point by up to 50 % may occur. The influence of the parameters contact pressure and flow rate on the MEA performance is discussed in this presentation. To investigate their impact, we analysed the MEAs in an electrolyser test station using polarisation curves, electrochemical impedance spectroscopy and load tests at constant current and constant voltage. Some of the results presented are obtained within the project “REVAL – reversible anion exchange membrane electrolysis” (funding code 03ZZ0732D) funded by the German Federal Ministry of Education and Research (BMBF).
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Noor Azam, Adam Mohd Izhan, Thuushren Ragunathan, Nurul Noramelya Zulkefli, et al. "Investigation of Performance of Anion Exchange Membrane (AEM) Electrolysis with Different Operating Conditions." Polymers 15, no. 5 (2023): 1301. http://dx.doi.org/10.3390/polym15051301.
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In this work, the performance of anion exchange membrane (AEM) electrolysis is evaluated. A parametric study is conducted, focusing on the effects of various operating parameters on the AEM efficiency. The following parameters—potassium hydroxide (KOH electrolyte concentration (0.5–2.0 M), electrolyte flow rate (1–9 mL/min), and operating temperature (30–60 °C)—were varied to understand their relationship to AEM performance. The performance of the electrolysis unit is measured by its hydrogen production and energy efficiency using the AEM electrolysis unit. Based on the findings, the operating parameters greatly influence the performance of AEM electrolysis. The highest hydrogen production was achieved with the operational parameters of 2.0 M electrolyte concentration, 60 °C operating temperature, and 9 mL/min electrolyte flow at 2.38 V applied voltage. Hydrogen production of 61.13 mL/min was achieved with an energy consumption of 48.25 kW·h/kg and an energy efficiency of 69.64%.
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Chang, Shing-Cheng, Ru-En Gu, and Yen-Hsin Chan. "Parameter Analysis of Anion Exchange Membrane Water Electrolysis System by Numerical Simulation." Energies 17, no. 22 (2024): 5682. http://dx.doi.org/10.3390/en17225682.
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Anion exchange membrane electrolysis, which combines the advantages of both alkaline electrolysis and proton-exchange membrane electrolysis, is a promising technology to reduce the cost of hydrogen production. The present work focused on the study of the electrochemical phenomena of AEM electrolysis and the investigation of the key factors of the AEM hydrogen production system. The numerical model is established according to electrochemical reactions, polarization phenomena, and the power consumption of the balance of plant components of the system. The effects of operation parameters, including the temperature and hydrogen pressure of the electrolyzer, electrolyte concentration, and hydrogen supply pressure on the energy efficiency are studied. The basic electrochemical phenomena of AEM water electrolysis cells are analyzed by simulations of reversible potential and activation, and ohmic and concentration polarizations. The results reveal that increasing the operating temperature and hydrogen production pressure of the AEM electrolyzer has positive effects on the system’s efficiency. By conducting an optimization analysis of the electrolyzer temperature—which uses the heat energy generated by the electrochemical reaction of the electrolyzer to minimize the power consumption of the electrolyte pump and heater—the AEM system with an electrolyzer operating at 328 K and 30 bar can deliver hydrogen of pressure up to 200 bar under an energy efficiency of 56.4%.
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Bernat, Rafal, Jaroslaw Milewski, Olaf Dybinski, Aliaksandr Martsinchyk, and Pavel Shuhayeu. "Review of AEM Electrolysis Research from the Perspective of Developing a Reliable Model." Energies 17, no. 20 (2024): 5030. http://dx.doi.org/10.3390/en17205030.
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This review thoroughly examines recent progress, challenges, and future prospects in the field of alkaline exchange membrane (AEM) electrolysis. This emerging technology holds promise for eco-friendly hydrogen production. It blends the benefits of traditional alkaline and proton-exchange membrane technologies, enhancing affordability and operational efficiencies by utilizing non-precious metal catalysts and operating at reduced temperatures. This study discusses key developments in materials, electrode design, and performance enhancement techniques. It also highlights the strategic role of AEM electrolysis in meeting global energy transition targets, like achieving Net Zero Emissions by 2050. An in-depth exploration of the operational fundamentals of AEM water electrolysis is provided, noting the technology’s early stage development and the ongoing need for research in membrane-electrode assembly assessment, catalyst efficiency, and electrochemical ammonia production. Moreover, this review compiles results on different cell components, electrolyte types, and experimental approaches, providing insights into operational parameters critical to optimizing AEM performance. The conclusion emphasizes the necessity for continuous research and commercialization efforts to exploit AEM electrolysis’s full potential across diverse industries.
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Vincent, Immanuel, Eun-Chong Lee, and Hyung-Man Kim. "Highly cost-effective platinum-free anion exchange membrane electrolysis for large scale energy storage and hydrogen production." RSC Advances 10, no. 61 (2020): 37429–38. http://dx.doi.org/10.1039/d0ra07190k.
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Anion exchange membrane (AEM) electrolysis eradicates platinum group metal electrocatalysts and diaphragms and is used in conventional proton exchange membrane (PEM) electrolysis and alkaline electrolysis.
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Kang, sun Young, Yong-Hun Cho, and Yung-Eun Sung. "Superior Performance and Durability Water Electrolysis with a Highly Conductive and Stable Anion-Exchange Membrane." ECS Meeting Abstracts MA2022-02, no. 40 (2022): 1477. http://dx.doi.org/10.1149/ma2022-02401477mtgabs.
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The commercialization of anion-exchange membrane water electrolysis (AEMWE) is important to produce low-cost and high-purity hydrogen. However, water electrolysis with an anion-exchange membrane (AEM) has limitations such as its poor stability and ionic conductivity, leading to low durability and performance of AEMWE. In this study, we developed superior-performance and stable AEMWE by employing an AEM without aryl-ether backbone structure. To achieve superior -performance and durable AEMWE, the effect of various parameters that is suitable for the adapted AEM was estimated. As a result, the AEM adapted in this work showed much better and was more durable than the conventional AEM (FAA-3). Moreover, it exhibited high efficiency under pure water feeding conditions. These results were contributed to high-efficient and durable AEM caused by its absence of aryl-ether backbone. This work suggests the potential use of polyphenylene structure as aryl-ether free backbone of AEM on AEMWE under alkaline solution and/or pure water condition.
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Ranz, Matthias, Bianca Grabner, Bernhard Schweighofer, Hannes Wegleiter, and Alexander Trattner. "Deciphering Anion Exchange Membrane Water Electrolysis: A Distribution of Relaxation Times Approach." ECS Transactions 114, no. 5 (2024): 483–92. http://dx.doi.org/10.1149/11405.0483ecst.
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Anion exchange membrane water electrolysis (AEM-WE) is a promising method for hydrogen production, offering advantages over proton exchange membrane water electrolysis (PEM-WE), such as the use of nonprecious metal catalysts and perfluorosulfonic acid free membranes. Despite achieving impressive current densities, challenges in efficiency and stability remain. This study employs electrochemical impedance spectroscopy (EIS), the equivalent circuit model (ECM) and distribution of relaxation times (DRT) analysis to investigate AEM-WE cells. DRT analysis identifies and quantifies five loss mechanisms within the AEM-WE system, including hydrogen and oxygen evolution reactions and ionic transport losses. Long-term experiments reveal catalyst degradation and its impact on performance, providing insights for targeted optimisation. The findings enhance understanding of the electrochemical processes in AEM-WE, offering pathways to improve stability and efficiency.
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Ranz, Matthias, Bianca Grabner, Bernhard Schweighofer, Hannes Wegleiter, and Alexander Trattner. "Deciphering Anion Exchange Membrane Water Electrolysis: A Distribution of Relaxation Times Approach." ECS Transactions 114, no. 5 (2024): 469–78. http://dx.doi.org/10.1149/11405.0469ecst.
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Anion exchange membrane water electrolysis (AEM-WE) is a promising method for hydrogen production, offering advantages over proton exchange membrane water electrolysis (PEM-WE), such as the use of nonprecious metal catalysts and perfluorosulfonic acid free membranes. Despite achieving impressive current densities, challenges in efficiency and stability remain. This study employs electrochemical impedance spectroscopy (EIS), the equivalent circuit model (ECM) and distribution of relaxation times (DRT) analysis to investigate AEM-WE cells. DRT analysis identifies and quantifies five loss mechanisms within the AEM-WE system, including hydrogen and oxygen evolution reactions and ionic transport losses. Long-term experiments reveal catalyst degradation and its impact on performance, providing insights for targeted optimisation. The findings enhance understanding of the electrochemical processes in AEM-WE, offering pathways to improve stability and efficiency.
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Hesse, Miriam, Enado Pineti, Bastian Kaufmann, et al. "Boosting Hydrogen Production: Non-Noble Metal Catalysts Optimize Electrodes in Anion Exchange Membrane Water Electrolysis." ECS Meeting Abstracts MA2024-02, no. 45 (2024): 3183. https://doi.org/10.1149/ma2024-02453183mtgabs.
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As the world transitions to renewable energy sources, efficient energy storage is crucial for managing power fluctuations and decarbonize crucial high temperature processes. Achieving grid balance and optimizing renewable energy capacity requires innovative solutions. One promising option is the conversion of electrical energy into hydrogen through Anion Exchange Membrane Water Electrolysis (AEM-WE). AEM-WE combines high hydrogen production rates per electrode area and little production site footprint of Proton Exchange Membrane Water Electrolysis (PEM-WE) with cost-effectiveness of non-noble electrode materials utilized in Alkaline Water Electrolysis (A-WE). To further optimize AEM-WE, it is essential to improve hydrogen production while reducing material costs. This can be achieved through innovative approaches to electrocatalyst and electrode design. However, developing cost-effective catalysts that combine superior efficiency and robustness in aqueous environments, ideally in alkaline conditions, remains a big challenge. In this work, two electrode preparation approaches are investigated. For the anodic OER a corrosion synthesis is been developed to form highly active NiFe-layered double hydroxide (LDH) structures on nickel non-woven porous transport layers (PTL). A highly active cell can be combined with a cathodic HER catalyst, prepared by electrochemical deposition Ni-S on a stainless steel non-woven PTL. In single cell AEM water electrolysis using 1 M KOH-solution utilizing the prepared NiFe-LDH anode and Pt/C cathode, 2.7 A/cm² at 2 V were achieved, surpassing commercially available powder catalysts like NiFe-oxide. Comparative analysis of Ni-S cathode with NiFe-LDH, integrated into a membrane electrode assembly demonstrated superior AEM-WE performance, outperforming the mentioned platinum on carbon catalysts. Electrochemical impedance spectra indicated higher charge transfer activity of Ni-S cathode compared to Pt/C. Importantly, the electrodes prepared in this study exhibited stability under accelerated electrochemical stress tests for 1000 cycles. These approaches provide a simple, inexpensive, scalable and therefore industry-relevant fabrication method with improved active areas and excellent catalytic activity during AEM water electrolysis. Figure 1
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Viviani, Marco, Dennis Rusitov, Rusudan Sulaberidze, et al. "Hydrocarbon Proton and Anion Exchange Polymers for Water Electrolysis Applications." ECS Meeting Abstracts MA2024-02, no. 43 (2024): 2878. https://doi.org/10.1149/ma2024-02432878mtgabs.
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Renewable energy and water electrolysis (WE) are deemed to be the pillars over which the incoming green hydrogen era and energy transition will stand. Water electrolysis can undergo in both acidic and alkaline conditions. In modern times, solid polymer electrolyte WE has attracted particular interest, due to the advantage of a compact design combined with the possibility to operate at higher pressure and temperatures even using pure water. Still to date, the most used membranes in PEMWE are poly(perfluorosulfonic) acids (PFSAs) (e.g., Nafion™) due to their mechanical strength, strong chemical resistance, and high proton conductivity. However, recent concerns regarding their cost, environmental impact due to fluorine chemistry, mechanical instability above 80 °C, and low gas barrier (especially H2) require urgent development of suitable hydrocarbon alternatives. Sulfonated poly(phenylene sulfones) (sPPS) represent a valuable hydrocarbon alternative to PFSAs as they exhibit lower gas crossover, higher conductivity, better thermal stability and low production cost.[1] [2] This class of polymer is able to outperform Nafion™ in PEMWE thanks to their higher proton conductivity (Fig. 1 b)).[1] To improve long term-stability of these polymers in operative PEMWE conditions (T = 80°C, > 1 Acm-2 ), fluorine-free reinforcement and Ce-based “damage-reparation”[3] strategies have been successfully implemented extending their stability in the range of thousands of hours. A major drawback of PEMWE technology is the reliance on platinum group metals (PGMs) (i.e. Pt and Ir). This stimulated the research of alternative strategies to respond to the demand of green H2 necessary to mitigate global warming reduction. AEMWE is the ideal alternative to PEMWE since it can be performed efficiently with non-PGMs, i.e., iron and nickel. The main shortcoming in AEMWE comes from the need of an alkaline electrolyte, which drastically limited the development of AEM technology in past decades. The harsh alkaline and electrochemical stress present in AEMWE have only recently been overcome by a new class of polyphenylene piperidinium and polynorbornene-based polymers which are also commercially available as Piperion™ and Pention™ respectively. The first are obtained by super-acidic Friedel-Craft addition[4] while the polynorbornene chemistry requires special catalysts.[5] Inspired by these results, in our lab, we have dedicated particular efforts to develop hydrocarbon AEM materials implementing phosphorous superbases as anion conducting functionalities to eliminate the presence of constant charges close to the polymer chain. AEMs based on polynorbornenes are proposed, including stable amino-linkage inspired by previous work.[6] Additionally, anion exchange ionomers (AEI) for catalyst layers with enhanced gas permeability were synthesized based on “canal” polynorbornene and novel crosslinked polyarylpiperidinium. The main synthetic strategies and properties (e.g., IEC, WU, alkaline resistance) of the resulting polymers are presented.
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Kim, Youngkeun, Yeonghyun Kim, Donggyun Lee, and Junghwan Kim. "Computational Modeling of Anion Exchange Membrane Water Electrolysis." ECS Meeting Abstracts MA2024-02, no. 50 (2024): 5097. https://doi.org/10.1149/ma2024-02505097mtgabs.
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Reducing greenhouse gas emissions in all sectors through energy transition using green hydrogen as renewable fuel is required to conform to Paris Climate Agreement. Anion exchange membrane (AEM) water electrolysis based on renewable energy sources is one of the promising strategies due to its cost effectiveness and absence of corrosion problem. However, proving the durability, reliability, and efficiency of AEM electrolysis is challenging. In this study, AEM electrolysis modeling based on computational fluid dynamics (CFD) was proposed for analyzing multi-dimensional and multi-phase phenomena inside the electrolysis cell. To guarantee the high fidelity of proposed model, parameter estimation and validation with lab-scale experimental data were conducted, showing high accuracy. Parameter estimation was performed through optimization-based approach and four system-dependent parameters were selected: anode / cathode roughness factor, membrane conductivity, and interfacial resistance. The result showed that the more hydrogen is observed in the outlet as the voltage increases while overall durability of cell reduces due to increase in temperature difference and pressure drop. The proposed model expected to show the enhanced performance if optimal flow patterns with operating conditions are found.
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Medveď, Dušan, Filip Juríni, and Dávid Martinko. "Fuel Production Design for Fuel Cells." Acta Electrotechnica et Informatica 23, no. 3 (2023): 27–32. http://dx.doi.org/10.2478/aei-2023-0014.
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Abstract In a world grappling with environmental challenges and the dire need for sustainable energy solutions, this study delves deep into the efficient production of HHO gas via an electrolyser. Recognizing the pivotal role of clean fuel alternatives, we aimed to harness the potential of electrolysis, specifically targeting domestic heating scenarios as a primary application. Through a systematic and comprehensive methodology, we embarked on constructing a functional electrolyser, further advancing its efficiency by means of various innovative strategies, ranging from optimal electrode designs to system configurations. Our research highlighted the potential of the electrolyser in reducing greenhouse gas emissions and minimizing natural gas consumption, thus underscoring its environmental benefits. Notably, this work distinguishes itself from previous literature by presenting both a detailed setup process and potential applications for the produced fuel. Moreover, by introducing enhanced efficiency measures, it sets a new standard in electrolyser construction and use. The results reiterate the feasibility of such a system even in household settings, portraying it as a robust answer to today’s energy challenges. In essence, this study serves as a beacon, calling for broader adoption of greener, more sustainable energy solutions.
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Xu, Ziqi, Sofia Delgado, Vladimir Atanasov, Tobias Morawietz, Aldo Saul Gago, and Kaspar Andreas Friedrich. "Novel Pyrrolidinium-Functionalized Styrene-b-ethylene-b-butylene-b-styrene Copolymer Based Anion Exchange Membrane with Flexible Spacers for Water Electrolysis." Membranes 13, no. 3 (2023): 328. http://dx.doi.org/10.3390/membranes13030328.
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Anion exchange membranes (AEM) are core components for alkaline electrochemical energy technologies, such as water electrolysis and fuel cells. They are regarded as promising alternatives for proton exchange membranes (PEM) due to the possibility of using platinum group metal (PGM)-free electrocatalysts. However, their chemical stability and conductivity are still of great concern, which is appearing to be a major challenge for developing AEM-based energy systems. Herein, we highlight an AEM with styrene-b-ethylene-b-butylene-b-styrene copolymer (SEBS) as a backbone and pyrrolidinium or piperidinium functional groups tethered on flexible ethylene oxide spacer side-chains (SEBS-Py2O6). This membrane reached 27.8 mS cm−1 hydroxide ion conductivity at room temperature, which is higher compared to previously obtained piperidinium-functionalized SEBS reaching up to 10.09 mS cm−1. The SEBS-Py206 combined with PGM-free electrodes in an AWE water electrolysis (AEMWE) cell achieves 520 mA cm−2 at 2 V in 0.1 M KOH and 171 mA cm−2 in ultra-pure water (UPW). This high performance indicates that SEBS-Py2O6 membranes are suitable for application in water electrolysis.
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Li, Lu. "(Digital Presentation) In-Situ Quantification of Individual Electrode Polarization and Depth Validation of the Distribution of Relaxation Times Methods Feasibility in PEM Fuel Cell." ECS Meeting Abstracts MA2024-02, no. 44 (2024): 3094. https://doi.org/10.1149/ma2024-02443094mtgabs.
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The article titled "Dynamics of anion exchange membrane electrolysis: Unravelling loss mechanisms with electrochemical impedance spectroscopy, reference electrodes and distribution of relaxation times" explores the challenges and mechanisms in anion exchange membrane water electrolysis (AEM-WE). The study by Matthias Ranz and colleagues employs electrochemical impedance spectroscopy (EIS), half-cell measurements using a reversible hydrogen electrode (RHE), and distribution of relaxation times (DRT) analysis to delve into the dynamics of AEM-WE cells. AEM-WE is gaining attention as a promising technology for hydrogen production due to its potential cost benefits over conventional electrolysis systems. However, its adoption faces obstacles such as efficiency issues and high degradation rates. To address these challenges, the research employs detailed electrochemical characterization techniques, providing new insights into the operational dynamics of AEM-WE cells. The study reveals five major loss mechanisms within AEM-WE systems: hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and ion transport losses, among others, occurring mostly within the catalyst layers. The findings also discuss the influence of various operating parameters on these loss mechanisms and how they can be systematically tracked and analyzed through EIS. A significant aspect of the research is the application of DRT analysis, a method not previously used in AEM-WE studies. This analysis method helps in identifying and quantifying the different electrochemical phenomena contributing to cell losses. By correlating these phenomena with their physicochemical origins, the study enhances understanding of the underlying processes within AEM-WE cells. Moreover, the use of equivalent circuit models in conjunction with EIS data provides a deeper understanding of the electrochemical behavior of the system. This combined approach allows for a more precise characterization of the impedance features and the differentiation of processes such as ion transport and electrochemical reactions. Ultimately, the research highlights the complexity of the AEM-WE process and emphasizes the need for advanced diagnostic tools to optimize performance and stability. By pinpointing the specific causes of efficiency losses and identifying opportunities for material and process improvements, the study contributes significantly to the development of more robust and efficient AEM-WE systems. In conclusion, the research not only elucidates the various loss mechanisms in AEM-WE but also showcases the potential of advanced electrochemical techniques like EIS and DRT in enhancing the understanding and optimization of this promising hydrogen production technology. This work sets a foundation for future studies aimed at overcoming the limitations of AEM-WE and advancing towards its commercial viability.
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Baranton, Steve, Robin Hu, Shazam Williams, et al. "Catalysts and Electrode Development for AEM Water Electrolysis." ECS Meeting Abstracts MA2024-02, no. 42 (2024): 2819. https://doi.org/10.1149/ma2024-02422819mtgabs.
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Water electrolysis is a promising technology that can use renewable energies (solar and wind) to produce green hydrogen [1]. In particular, Anion Exchange Membrane Water Electrolysis (AEMWE) offers the combined advantages of the mature Alkaline Water Electrolysis technology and the high efficiency and high dynamic range of the Proton Exchange Membrane Water Electrolysis [2]. This combination of advantages allows the AEMWE technology to be operated with non-PGM electrodes [3], non-perfluorinated membrane with a high dynamic range favoring its use with intermittent renewable energy for the production of green hydrogen. The development of AEMWE requires production of efficient catalytic materials at industrial scale and integration in membrane electrode assemblies (MEAs). In this work, we have developed three families of non-noble catalysts: nickel based materials, iron free catalysts [4, 5] and high entropy materials. They are designed for both anode and cathode of AEM electrolyzers. High performances cathodes are developed with low PGM loading alloy catalysts. These materials (cathode and anode) are produced with highly scalable synthesis methods involving water as solvent and the reactants used are low-cost, widely available chemical compounds. The catalysts obtained are high surface area (up to 100 m2/g) nanostructured materials, ensuring a high catalytic activity for AEMWE electrodes. The development of different catalyst families allows the optimization of electrodes in a wide range of operating conditions (temperature, nature of the membrane and hydroxide concentration in the circulating electrolyte) Catalyst application is critical for preparing efficient MEA’s. The catalyst coating has been performed in two configurations: catalyst coated substrate (CCS) and catalyst coated membrane (CCM). In both configurations, the ink formulation is optimized to improve the catalyst dispersion and the catalyst/polymer coating on the substrate or membrane. The best coating conditions have been determined for both anodes and cathodes to prepare electrodes that improve the catalyst performances. This phase is crucial to avoid negative interactions between the different components of the electrode [6] and create a good interface with the membrane. The resulting MEAs were tested in our electrolyzer with different configurations (5 and 50 cm2) for performance and durability in a temperature range from 60°C to 80°C. Depending on the operating conditions and the catalyst families chosen, the performance exceeded 3 A/cm2 with a cell voltage below 2 V (Figure 1). [1] M. Chatenet, B. G. Pollet, D. R. Dekel, F. Dionigi, J. Deseure, P. Millet, R. D. Braatz, M. Z. Bazant, M. Eikerling, I. Staffell, P. Balcombe, Y. Shao-Horn, H. Schäfer, Water electrolysis: from textbook knowledge to the latest scientific strategies and industrial developments, Chem. Soc. Rev., 2022, 51, 4583–4762 [2] H. A. Miller, K. Bouzek, J. Hnat, S. Loos, C. I. Bernäcker, T. Weißgärber, L. Rontzsch, J. Meier-Haack, Green hydrogen from anion exchange membrane water electrolysis: a review of recent developments in critical materials and operating conditions, Sustainable Energy Fuels, 2020, 4, 2114–2133 [3] E. Cossar, F. Murphy, E. A. Baranova, Nickel-based anodes in anion exchange membrane water electrolysis: a review, J. Chem. Technol. Biotechnol., 2022, 97, 1611–1624 [4] A. F. Staerz, M. van Leeuwen, T. Priamushko, T. Saatkamp, B. Endrődi, N. Plankensteiner, M. Jobbagy, S. Pahlavan, M. J. W. Blom, C. Janáky, S. Cherevko, P. M. Vereecken, Effects of Iron Species on Low Temperature CO2 Electrolyzers, Angew. Chem. Int. Ed., 2024, 63, e202306503 [5] G. A. Lindquist, Q. Xu, S. Z. Oener, S. W. Boettcher, Membrane Electrolyzers for Impure-Water Splitting, Joule 2020, 4, 2549–2561 [6] E. Cossar, F. Murphy, J. Walia, A. Weck, E. A. Baranova, Role of Ionomers in Anion Exchange Membrane Water Electrolysis: Is Aemion the Answer for Nickel-Based Anodes?, ACS Appl. Energy Mater. 2022, 5, 9938−9951 Figure 1
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Faid, Alaa, Alejandro Oyarce Barnett, Frode Seland, and Svein Sunde. "Highly Active Nickel-Based Catalyst for Hydrogen Evolution in Anion Exchange Membrane Electrolysis." Catalysts 8, no. 12 (2018): 614. http://dx.doi.org/10.3390/catal8120614.
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Anion exchange membrane (AEM) electrolysis is hampered by two main issues: stability and performance. Focusing on the latter, this work demonstrates a highly active NiMo cathode for hydrogen evolution in AEM electrolysis. We demonstrate an electrolyzer performance of 1 A cm−2 at 1.9 V (total cell voltage) with a NiMo loading of 5 mg cm−2 and an iridium black anode in 1 M KOH at 50 °C, that may be compared to 1.8 V for a similar cell with Pt at the cathode. The catalysts developed here will be significant in supporting the pursuit of cheap and environmentally friendly hydrogen fuel.
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Alia, Shaun M., Saad Intikhab, Mai-Anh Ha, and Shraboni Ghoshal. "(Invited) Materials Integration, Durability, and Perspectives in Anion Exchange Membrane-Based Low Temperature Electrolysis." ECS Meeting Abstracts MA2022-01, no. 33 (2022): 1337. http://dx.doi.org/10.1149/ma2022-01331337mtgabs.
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As an energy carrier, hydrogen has unique advantages due to its high energy density, ability for long-term storage, and the ability to convert between chemical bonds and electricity. [1] Although hydrogen currently has a small role in energy pathways, decreasing electricity prices can allow for a significant growth opportunity. Compared to alkaline electrolysis, anion exchange membrane (AEM) systems utilize zero-gap membrane electrode assemblies that improve performance and potentially enable hydrogen compression with back pressure. Compared to proton exchange membrane (PEM) systems, the high pH of AEMs allows for non-platinum group metal (non-PGM) catalysts and component coatings (transport layers, separators) that can reduce system cost and improve long-term durability. This presentation includes on an overview of NREL efforts in AEM electrolysis, and focuses on operation choices, materials integration, and catalysis. In recent years, membrane advancements have enabled higher AEM performance, particularly in supporting electrolytes. [2] Testing has included supported and unsupported (water) feeds, and operational strategies largely depend on the intended market. Efforts have been made to investigate the role supporting electrolytes play in improving AEM performance and assess the viability of AEM as a PEM replacement through water-only feeds and dry-cathode operation. [3,4] Materials integration focuses on strategies for incorporating catalysts and ionomers that have improved water performance and allowed for short-term durability testing. [3] These efforts include coating approaches and processing conditions to rearrange catalyst layers, and detail the complications of developing protocol recommendations with component changes. In catalysis, fundamental studies have improved an understanding of materials requirements in the oxygen and hydrogen evolution reactions, and the impact of ionomer interactions on reactivity. Ab-initio simulations have provided feedback into low- and non-PGM catalyst development studies that improve device-level kinetics. Perspectives in AEM electrolysis will be discussed, and include ongoing needs for component development and durability testing, to separate and accelerate relevant degradation mechanisms. References [1] B. Pivovar, N. Rustagi, S. Satyapal, The Electrochemical Society Interface 2018, 27, 47. [2] G. Bender, H. Dinh, HydroGEN: Low-Temperature Electrolysis (LTE) and LTE/Hybrid Supernode, https://www.hydrogen.energy.gov/pdfs/review20/p148a_bender_2020_o.pdf 2020. [3] S. M. Alia, HydroGEN: Low Temperature Electrolysis, https://www.hydrogen.energy.gov/pdfs/review21/p148a_alia_2021_p.pdf 2021. [4] S. Ghoshal, B. S. Pivovar, S. M. Alia, J. Power Sources 2021, 488, 229433.
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Vincent, Immanuel, Ekain Fernandez, Fernandez Carretero Francisco Jose, Ion Velasco, and Alberto Garcia. "(Invited) Current Status and Progress in Anion Exchange Membrane Electrolysis." ECS Meeting Abstracts MA2023-02, no. 48 (2023): 2426. http://dx.doi.org/10.1149/ma2023-02482426mtgabs.
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Anion exchange membrane (AEM) electrolysis is a promising solution for large-scale hydrogen production from renewable energy resources. However, the performance of AEM electrolysis is still lower than what can be achieved with conventional technologies. Materials chemistry, MEA designs, and optimal operation conditions have driven recent advancements. Majority of the AEM research has focused on improving ionic conductivity and alkaline stability. Many AEMs exceed 0.1 S/cm (at 60–80 °C), however stability at temperatures above 60 °C needs improvement. Oxygen evolution reaction OER remains a bottleneck. The active-site mechanism of NiFe catalysts is disputed, and their long-term stability is unknown. Co boosts NiFe catalyst conductivity. Carbon-supported Pt dominates the hydrogen evolution process (HER), whereas PtNi alloys and clusters of Ni(OH)2 on Pt compete. Well-dispersed Ru nanoparticles on functionalized high-surface-area carbon substrates show promising HER actions. New in situ methods, AEMWE evaluation processes, and catalyst-structure designs could help the field advance faster. Nonetheless, single AEM water electrolyzer cells have operated for several thousand hours at 60 °C and 1 A/cm2.
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Chan, Ai-Lin, Arielle L. Clauser, Melissa E. Kreider, Emily K. Volk, Josh D. Sugar, and Shaun M. Alia. "Investigation on the Interaction of Catalyst and Ionomer in AEM Electrolysis." ECS Meeting Abstracts MA2024-02, no. 43 (2024): 2884. https://doi.org/10.1149/ma2024-02432884mtgabs.
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In low temperature electrolysis, anion exchange membrane (AEM) systems combine the advantages of alkaline and proton exchange membrane (PEM) electrolysis in generating high purity hydrogen and reducing material costs from catalysts and component coatings [1]. Recent studies in AEM electrolysis have focused on improving cell performance, minimizing catalyst dissolution and mitigating ionomer/membrane degradation with different operating conditions. Ionomers play a critical role in the electrode because they provide ion conductivity, enhance mechanical support, and create preferred morphologies for electrolyte and produced gas to move [2, 3]. Optimizing catalyst-ionomer interactions by varying ionomer content, chemistries, and forms can accelerate the development of AEM electrolysis in terms of performance enhancement, cost and lifetime. In this work, different forms of ionomer (powdered and dispersed) with two polymer backbones were evaluated in AEM electrolysis cell testing. Ni- and Co-based oxides and IrO2 were applied as anode catalysts. In Figure 1, the anodes with powdered ionomer outperform the dispersed samples. With Co3O4 catalyst, the overpotential can be improved by 0.9 V at 1 A/cm2 (iR-free voltage of Co3O4 with powdered ionomer: 1.68 V at 1 A/cm2). By electrochemical diagnostic and modeling methods, the improved performance with powdered ionomer is attributed to better reaction kinetic from more active area between catalysts and ionomers, less ohmic overpotentials due to better contact between the electrode and the transport layer and preferred transport properties with higher porosity created by powdered ionomer. Scanning electron microscopy data verifies that the anodes with powdered ionomer provide more homogeneous distribution of catalysts and ionomer in the electrode, while dispersed samples have the issues of agglomerates and uneven coverage of catalysts, which could worsen the catalyst utilization and trigger mass transport issues. [1] Ayers, Katherine, et al. "Perspectives on low-temperature electrolysis and potential for renewable hydrogen at scale." Annual review of chemical and biomolecular engineering 10 (2019): 219-239. [2] Lee, Sol A., et al. "Anion exchange membrane water electrolysis for sustainable large‐scale hydrogen production." Carbon Neutralization 1.1 (2022): 26-48. [3] Favero, Silvia, Ifan EL Stephens, and Maria‐Magdalena Titirci. "Anion Exchange Ionomers: Design Considerations and Recent Advances‐An Electrochemical Perspective." Advanced Materials 36.8 (2024): 2308238. Figure 1
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Yanagibashi, Naoki, Shinya Nagatsuka, Yuki Ozawa, et al. "Development of Highly Durable Anion Exchange Membrane and the Utility for Aemwe Cells." ECS Meeting Abstracts MA2024-02, no. 43 (2024): 2952. https://doi.org/10.1149/ma2024-02432952mtgabs.
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Anion exchange membrane water electrolysis is of great interest in terms of the environmental impact and the cost because it does not need precious metal-based catalysts and corrosion-resistant components. But, it is difficult to satisfy all the performance requirements for anion exchange membranes (AEMs). There are three major performance requirements for AEMs, high ion conductivity, high durability, and low cost and so on. Therefore, further development of AEMs is still needed. Yamaguchi et al. have been researched the polyfluorene-based AEMs with high alkaline durability [1,2]. We are working on the practical application of their AEMs technology, and have been improving quality by optimizing the synthesis process and examining the film forming method, and examining scale-up for cost reduction. In addition, we prepared the test stand to evaluate the water electrolysis performance of AEMs, and we expanded our water electrolysis evaluation technology by introducing spray coater for the catalyst layer optimizing that of formation process, and the water electrolysis evaluation system. Based on the report by Yamaguchi et al., we developed the AEM. The water electrolysis performance of the MEA using the AEM was below 1.75V at 1A/cm2 in 1M KOH solution at 80℃, which is equivalent to that of commercial AEMs. To compare the durability of AEMs, the water electrolysis performance was evaluated after soaking in 1M KOH solution at 80℃. Water electrolysis performance after durability test was better than that of commercial aromatic AEMs(Figure.1(a)). The performance of the AEM was slightly changed at 200 hours, but after that, there was almost no change in the performance at 2000 hours, and the increase in voltage was less than 3% compared to the initial performance(Figure.1(b)). On the other hand, the voltage of commercially available aromatic AEM increased by 140% at 1000 hours. We confirmed the high durability of the polyfluorene-based AEMs. For the future, we would like to show the superiority of the AEMs in the continuous data of the water electrolysis durability test in the cell. References [1] Miyanishi, T. Yamaguchi, Highly conductive mechanically robust high Mw polyfluorene anion exchange membrane for alkaline fuel cell and water electrolysis application, Polym. Chem. 11.3812-3820, 2020, DOI: 10.1039/D0PY00334D [2] T. Yamaguchi et al, An Extremely Low Methanol Crossover and Highly Durable Aromatic Pore-Filling Electrolyte Membrane for Direct Methanol Fuel Cells, Advanced Materials 19, pp. 592–596 ,2007 Figure1. The water electrolysis performance measured after soaking 1M KOH solution. (a) i-V curve after durability test (b) Voltage retention rate against durability time Figure 1
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Rozendal, R. A., T. H. J. A. Sleutels, H. V. M. Hamelers, and C. J. N. Buisman. "Effect of the type of ion exchange membrane on performance, ion transport, and pH in biocatalyzed electrolysis of wastewater." Water Science and Technology 57, no. 11 (2008): 1757–62. http://dx.doi.org/10.2166/wst.2008.043.
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Previous studies have shown that the application of cation exchange membranes (CEMs) in bioelectrochemical systems running on wastewater can cause operational problems. In this paper the effect of alternative types of ion exchange membrane is studied in biocatalyzed electrolysis cells. Four types of ion exchange membranes are used: (i) a CEM, (ii) an anion exchange membrane (AEM), (iii) a bipolar membrane (BPM), and (iv) a charge mosaic membrane (CMM). With respect to the electrochemical performance of the four biocatalyzed electrolysis configurations, the ion exchange membranes are rated in the order AEM &gt; CEM &gt; CMM &gt; BPM. However, with respect to the transport numbers for protons and/or hydroxyl ions (tH/OH) and the ability to prevent pH increase in the cathode chamber, the ion exchange membranes are rated in the order BPM &gt; AEM &gt; CMM &gt; CEM.
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Pushkarev, Artem S., Irina V. Pushkareva, Stephanus P. du Preez, and Dmitri G. Bessarabov. "PGM-Free Electrocatalytic Layer Characterization by Electrochemical Impedance Spectroscopy of an Anion Exchange Membrane Water Electrolyzer with Nafion Ionomer as the Bonding Agent." Catalysts 13, no. 3 (2023): 554. http://dx.doi.org/10.3390/catal13030554.
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Low-cost anion exchange membrane (AEM) water electrolysis is a promising technology for producing “green” high-purity hydrogen using platinum group metal (PGM)-free catalysts. The performance of AEM electrolysis depends on the overall overvoltage, e.g., voltage losses coming from different processes in the water electrolyzer including hydrogen and oxygen evolution, non-faradaic charge transfer resistance, mass transfer limitations, and others. Due to the different relaxation times of these processes, it is possible to unravel them in the frequency domain by electrochemical impedance spectroscopy. This study relates to solving and quantifying contributions to the total polarization resistance of the AEM water electrolyzer, including ohmic and charge transfer resistances in the kinetically controlled mode. The high-frequency contribution is proposed to have non-faradaic nature, and its conceivable nature and mechanism are discussed. The characteristic frequencies of unraveled contributions are provided to be used as benchmark data for commercially available membranes and electrodes.
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Xu, Hui, Thomas Stracensky, Ankur Gupta, et al. "(Invited) AEM Water Electrolysis: From Materials to System." ECS Meeting Abstracts MA2024-02, no. 47 (2024): 3240. https://doi.org/10.1149/ma2024-02473240mtgabs.
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Anion exchange membrane water electrolysis (AEMWE) is an electrolysis technology that combines the advantages of alkaline liquid electrolysis (ALE) and proton exchange membrane water electrolysis (PEMWE). Specifically, AEMWE may eliminate or reduce the usage of expensive platinum metal group (PGM) catalysts, like its ALE counterpart, while also able to operate at high current density, non-balanced hydrogen pressure, and under dynamic loads, like PEMWE. However, AEMWE has not gained viability in commercial applications due to multiple challenges. From the materials perspective, both electrodes and membrane need further development. Although the oxygen evolution reaction (OER) catalysts for the anode have been studied at a rotating disk electrode (RDE) level for decades, seeing massive improvement in activities, their applications in the real working AEMWE still needs improvement. One challenge that has not been sufficiently addressed is poor adhesion between the substrate and the catalyst coating, which may fall off due to the force of bubbles formed on the surface of electrodes. While many different catalyst coating methodologies have been tried, the pore size and microstructure of the substrates plays an essential role for the quality of the coating and thus the electrode's stability. In addition, the membrane also has some unsolved problems like poor mechanical strength and chemical stability that compromises the longevity of the electrolyzer. It was also found that the interface between the membrane and electrode is crucial to the long durability of the AEMWE. One solution to this is the development of thermally processable AEMs, which can not only elevate the electrolyzer operating temperatures, but also form a better electrode/membrane interface. From the system point of view, the stack build needs to consider frames, sealing, pressure vessel, manifold, and shunt current, particularly when the AEMWE operates with the addition of electrolyte (e.g., KOH). Increasing the efficiency of the stack requires minimizing the shunt current, which is affected by the concentration of KOH, the manifold design, and the number of cells in a stack. Lowering electrolyte concentration is instrumental for reducing the shunt current but can be detrimental for the electrolyzer performance. Engineering solutions, such as using an extremal manifold design can tremendously reduce the shunt current, allowing for higher concentration of electrolyte and better performance. Finally, the successful non-balanced pressure operation (up to 50 bar) is not only determined by the membrane strength, but also the morphology of the supporting substrates like porous transport layers and the quality of assembly. These concepts will be validated in our 50 kW AEMWE stack and inform our 1 MW AEMWE design.
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Guruprasad, Naveen, Thijs Theodorus de Groot, and John van der Schaaf. "The Power of Reference Electrodes in AEM Electrolysis." ECS Meeting Abstracts MA2023-02, no. 42 (2023): 2071. http://dx.doi.org/10.1149/ma2023-02422071mtgabs.
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The use of reference electrodes is a powerful diagnostic tool to determine the overpotentials associated with oxygen and hydrogen evolution reaction. Yet, the use of reference electrodes in flow cells is still uncommon and provides several challenges especially related to the stability of the potential of the reference electrode. This study investigates the use of a reference electrode in a well-performing iridium-free AEM flow cell with a cell potential of <1.8 V @ 1.5 A cm-2. The reference electrode consists of electrically insulating foil with two platinum wire electrodes on one side as shown in Figure 1(left). A small micro-current is passed through the platinum wires to maintain hydrogen coverage on the reference electrode to establish equilibrium cell potential. The use of the reference electrode shows that the platinum-ruthenium cathode performs particularly well with an overpotential of <0.1 V @ 0.2 A cm-2. The reference electrode also is useful for the study of cell degradation. One of the major challenges of coupling electrolyzer directly to renewables are reverse currents flowing after shutdown in alkaline and AEM electrolyzers [1]. In this study, polarities were reversed to simulate these reverse currents. This lead to a significant increase in cell potential. It is clearly evident from Figure 1(right) that the cathode overpotentials increased significantly after this reverse current application, thereby indicating that the platinum-ruthenium cathode is vulnerable to reverse currents. [1]Ashraf Haleem et al, Effects of operation and shutdown parameters and electrode materials on the reverse current phenomenon in alkaline water analyzers, Journal of Power Sources, Volume 535, 2022, 231454, ISSN 0378-7753, https://doi.org/10.1016/j.jpowsour.2022.231454 Figure 1