Water management in anion-exchange membrane water electrolyzers under dry cathode operation

Koch, Susanne; Disch, Joey; Kilian, Sophia K.; Han, Yiyong; Metzler, Lukas; Tengattini, Alessandro; Helfen, Lukas; Schulz, Michael; Breitwieser, Matthias; Vierrath, Severin

doi:10.1039/d2ra03846c

Cited by 13 publications

(17 citation statements)

References 18 publications

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“…Modelling [71] and neutron imaging of both CO 2 E and AEM-WE systems [72,73] have both shown localized dehydration of the AEM at the interface with the catalyst layer due to high rates of water consumption at high current densities. It is therefore hypothesized that increasing the current distribution within the cathode might alleviate localized dehydration at the interface.…”

Section: Synergistic Effects Of the Cathode Composition And Membrane ...mentioning

confidence: 99%

Performance and Stability of Aemion and Aemion+ Membranes in Zero‐Gap CO₂ Electrolyzers with Mild Anolyte Solutions

et al. 2023

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The dependence of performance and stability of a zero-gap CO 2 electrolyzer on the properties of the anion exchange membrane (AEM) is examined. This work firstly assesses the influence of the anolyte when using an Aemion membrane and then shows that when using 10 mM KHCO 3 , a CO 2 electrolyzer using a nextgeneration Aemion + membrane can achieve lower cell voltages and longer lifetimes due to increased water permeation. The impact of lower permselectivity of Aemion + on water transport is also discussed. Using Aemion + , a cell voltage of 3.17 V at 200 mA cm À 2 is achieved at room temperature, with a faradaic efficiency of > 90 %. Stable CO 2 electrolysis at 100 mA cm À 2 is demonstrated for 100 h, but with reduced lifetime at 300 mA cm À 2 . However, the lifetime of the cell at high current densities is shown to be increased by improving water transport characteristics of the AEM and reducing dimensional swelling, as well as by improving cathode design to reduce localized dehydration of the membrane.

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Section: Synergistic Effects Of the Cathode Composition And Membrane ...mentioning

confidence: 99%

Performance and Stability of Aemion and Aemion+ Membranes in Zero‐Gap CO₂ Electrolyzers with Mild Anolyte Solutions

et al. 2023

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“…Neutron imaging is a valuable complement to X-ray imaging, since neutrons can penetrate common metals while attenuating hydrogen, lithium, and water. This feature makes neutron imaging an attractive technique for characterizing various electrochemical systems, including fuel cells, water electrolyzers, unitized reversible fuel cells, and CO 2 electrolyzers . Moreover, neutron imaging is particularly well-suited for imaging fuel cells and electrolyzers since neutrons can penetrate conventional hardware without requiring special equipment or design modifications.…”

Section: Why We Need X-ray Ct In Electrocatalysismentioning

confidence: 99%

A Viewpoint on X-ray Tomography Imaging in Electrocatalysis

et al. 2023

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With the emerging demands for clean energy and an economy with net-zero greenhouse gas emissions, electrocatalysis areas have attracted tremendous interest in recent years. The electrochemical devices that use electrocatalysis, such as fuel cells, electrolyzers, and flow batteries, consist of hierarchical structures, requiring comprehension and rational designs across scales from millimeter and micrometer all the way down to atomic scale. In past decades, electron microscopy techniques such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been extensively utilized for imaging different scales of these devices in both two and three dimensions. However, electron-based techniques for high-resolution imaging require uninterrupted maintenance of a high-vacuum environment, leading to difficulties of sample preparation and lack of integrated observation without intrusion/ disassembly. To overcome these disadvantages, more and more efforts have been dedicated to the development of X-ray imaging techniques recently, specifically absorption-based two-dimensional (2D) transmission X-ray microscopy and three-dimensional (3D) X-ray tomography, due to much better transmission behaviors of X-rays than electrons. X-ray tomography imaging mostly focuses on answering questions related to morphology and morphological changes at the microscale or near 1 μm resolution and nanoscale of 30 nm resolution. The method is nondestructive and it allows for the visualization of operando electrochemical devices, such as fuel cells, electrolyzers, and redox flow batteries. Operando X-ray microscopic tomography typically focuses on catalyst layers and morphology changes during degradation, as well as mass transport. Nanoscale tomography still predominantly is used for ex situ studies, as multiple challenges exist for operando studies implementation, including X-ray beam damage, sample holder design, and beamline availability. Both microscale and nanoscale tomography beamlines now couple various spectroscopic techniques, enabling electrocatalysis studies for both morphology and chemical transformations. This viewpoint highlights the recent advances in X-ray tomography for electrocatalysis, compares it to other tomographic techniques, and outlines key complementary techniques that can provide additional information during imaging. Lastly, it provides a perspective of what to anticipate in coming years regarding the method use for electrocatalysis studies.

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“…Thus, the presence of water molecules in the first solvation sphere of the OH − anions is a major parameter affecting AEMs stability. 17,35,46−48 In an AEMFC operated under practical current densities (≥400 mA cm −2 ) or AEMWE (in dry cathode operation mode), 49,50 the water consumption at the cathode side is highly increased, and microsolvation of OH − anions is reduced to very low levels (ca. λ = 2).…”

Section: ■ Introductionmentioning

confidence: 99%

“…Aiming to overcome these stability issues, several polymeric backbones have been synthesized and reported in the literature, such as polyethersulfone, polyfluoro-olefins, and poly(norbornene). − In addition, most research into AEM stability improvements focused on developing of new QA chemistries. ,− AEMs containing benzyltrimethylammonium (BTMA), the most commonly studied QA, can, however, exhibit decent alkaline stability in AEM form, especially when fully hydrated. − Currently, the main issue is the lack of test condition standardization: most alkaline stability testing is carried out at extremely high hydration, e.g ., λ > 50 (λ = water molecules/OH – molecules). − Even if an ex situ stability test is conducted with concentrated aqueous solutions (up to 10 M), − the high number of water molecules around the OH – anions (λ ≥ 6) may cause the AEM to appear stable, while actually be unstable in operando tests. Thus, the presence of water molecules in the first solvation sphere of the OH – anions is a major parameter affecting AEMs stability. ,,− In an AEMFC operated under practical current densities (≥400 mA cm –2 ) or AEMWE (in dry cathode operation mode), , the water consumption at the cathode side is highly increased, and microsolvation of OH – anions is reduced to very low levels ( ca . λ = 2) .…”

Section: Introductionmentioning

confidence: 99%

Alkaline Stability of Anion-Exchange Membranes

Willdorf-Cohen

Zhegur-Khais

Ponce-González

et al. 2023

ACS Appl. Energy Mater.

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Recently, the development of durable anion-exchange membrane fuel cells (AEMFCs) has increased in intensity due to their potential to use low-cost, sustainable components. However, the decomposition of the quaternary ammonium (QA) cationic groups in the anion-exchange membranes (AEMs) during cell operation is still a major challenge. Many different QA types and functionalized polymers have been proposed that achieve high AEM stabilities in strongly alkaline aqueous solutions. We previously developed an ex situ technique to measure AEM alkaline stabilities in an environment that simulates the low-hydration conditions in an operating AEMFC. However, this method required the AEMs to be soluble in DMSO solvent, so decomposition could be monitored using 1H nuclear magnetic resonance (NMR). We now report the extension of this ex situ protocol to spectroscopically measure the alkaline stability of insoluble AEMs. The stability ofradiation-grafted (RG) poly(ethylene-co-tetrafluoroethylene)-(ETFE)-based poly(vinylbenzyltrimethylammonium) (ETFE-TMA) and poly(vinylbenzyltriethylammonium) (ETFE-TEA) AEMs were studied using Raman spectroscopy alongside changes in their true OH– conductivities and ion-exchange capacities (IEC). A crosslinked polymer made from poly(styrene-co-vinylbenzyl chloride) random copolymer and N,N,N′,N′-tetraethyl-1,3-propanediamine (TEPDA) was also studied. The results are consistent with our previous studies based on QA-type model small molecules and soluble poly(2,6-dimethylphenylene oxide) (PPO) polymers. Our work presents a reliable ex situ technique to measure the true alkaline stability of AEMs for fuel cells and water electrolyzers.

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Water management in anion-exchange membrane water electrolyzers under dry cathode operation

Abstract: Dry cathode operation is a desired operation mode in anion-exchange membrane water electrolyzers, but water management is crucial. This is visualized using high-resolution neutron radiography and the ion-exchange capacity of the cathode ionomer is varied.

Cited by 13 publications

References 18 publications

Performance and Stability of Aemion and Aemion+ Membranes in Zero‐Gap CO₂ Electrolyzers with Mild Anolyte Solutions

Performance and Stability of Aemion and Aemion+ Membranes in Zero‐Gap CO₂ Electrolyzers with Mild Anolyte Solutions

A Viewpoint on X-ray Tomography Imaging in Electrocatalysis

Alkaline Stability of Anion-Exchange Membranes

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Water management in anion-exchange membrane water electrolyzers under dry cathode operation

Abstract: Dry cathode operation is a desired operation mode in anion-exchange membrane water electrolyzers, but water management is crucial. This is visualized using high-resolution neutron radiography and the ion-exchange capacity of the cathode ionomer is varied.

Cited by 13 publications

References 18 publications

Performance and Stability of Aemion and Aemion+ Membranes in Zero‐Gap CO2 Electrolyzers with Mild Anolyte Solutions

Performance and Stability of Aemion and Aemion+ Membranes in Zero‐Gap CO2 Electrolyzers with Mild Anolyte Solutions

A Viewpoint on X-ray Tomography Imaging in Electrocatalysis

Alkaline Stability of Anion-Exchange Membranes

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Product

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Performance and Stability of Aemion and Aemion+ Membranes in Zero‐Gap CO₂ Electrolyzers with Mild Anolyte Solutions

Performance and Stability of Aemion and Aemion+ Membranes in Zero‐Gap CO₂ Electrolyzers with Mild Anolyte Solutions