Understanding the microstructure of a core–shell anode catalyst layer for polymer electrolyte water electrolysis

Angelis, Salvatore De; Schuler, Tobias; Sabharwal, Mayank; Holler, Mirko; Guizar‐Sicairos, Manuel; Müller, E.; Büchi, Félix N.

doi:10.1038/s41598-023-30960-x

Cited by 9 publications

(15 citation statements)

References 42 publications

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“…While this was only vaguely discussed by the authors, it can be assumed that the initial mass transport must occur through the CL itself. In a recent study, De Angelis et al characterized the 3D structure of a typical PEWE CL via high-resolution ptychographic X-ray imaging, showing porosities that are in the range of ∼40%, therefore high enough to ensure fluidic transport.…”

Section: Resultsmentioning

confidence: 99%

“…While this seems to be a reasonable deduction due to the poor electronic IP conductivity of typical PEWE CLs, the authors did not discuss the effect of mass transport under the PTL lands. It is known from the literature, − that the CL has porosities in the range of 15–70% depending on the ionomer content, and therefore IP mass transport can occur even without direct contact with the open pore space of the PTL.…”

Section: Introductionmentioning

confidence: 99%

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How the Porous Transport Layer Interface Affects Catalyst Utilization and Performance in Polymer Electrolyte Water Electrolysis

Weber

Wrubel

Gubler

et al. 2023

ACS Appl. Mater. Interfaces

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Cost reduction and fast scale-up of electrolyzer technologies are essential for decarbonizing several crucial branches of industry. For polymer electrolyte water electrolysis, this requires a dramatic reduction of the expensive and scarce iridium-based catalyst, making its efficient utilization a key factor. The interfacial properties between the porous transport layer (PTL) and the catalyst layer (CL) are crucial for optimal catalyst utilization. Therefore, it is essential to understand the relationship between this interface and electrochemical performance. In this study, we fabricated a matrix of two-dimensional interface layers with a well-known model structure, integrating them as an additional layer between the PTL and the CL. By characterizing the performance and conducting an in-depth analysis of the overpotentials, we were able to estimate the catalyst utilization at different current densities, correlating them to the geometric properties of the model PTLs. We found that large areas of the CL become inactive at increasing current density either due to dry-out, oxygen saturation (under the PTL), or the high resistance of the CL away from the pore edges. We experimentally estimated the water penetration in the CL under the PTL to be ≈20 μm. Experimental results were corroborated using a 3D-multiphysics model to calculate the current distribution in the CL and estimate the impact of membrane dry-out. Finally, we observed a strong pressure dependency on performance and high-frequency resistance, which indicates that with the employed model PTLs, a significant gas phase accumulates in the CL under the lands, hindering the distribution of liquid water. The findings of this work can be extrapolated to improve and engineer PTLs with advanced interface properties, helping to reach the required target goals in cost and iridium loadings.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

How the Porous Transport Layer Interface Affects Catalyst Utilization and Performance in Polymer Electrolyte Water Electrolysis

Weber

Wrubel

Gubler

et al. 2023

ACS Appl. Mater. Interfaces

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“…One more imaging research interest is to distinguish electrode components within assemblies, which may require combination of Xray CT and other imaging characterization techniques such as ptychography and fluorescence. A recent example is the 2023 report by De Angelis et al 48 on their core−shell titaniasupported iridium oxide materials. As Figure 5 shows, the ptychography tomograph data acquired at the Swiss Light Source X12SA beamline segmented all four phases in the electrode: pores, ionomers, titanium oxide substrate, and iridium oxide that were coated on the TiO 2 surface.…”

Section: Why We Need X-ray Ct In Electrocatalysismentioning

confidence: 99%

“…Two-dimensional slice obtained from the entire ptychography tomogram showing all phases present in the PEMWE electrode. [Reprinted from ref . Open access under Creative Commons CC BY license.…”

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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“…Nevertheless, the main challenge relies upon sustaining good electrical conductivity and catalytic activity of PEMWE anode catalyst layers. [ 17–19 ]…”

Section: Introductionmentioning

confidence: 99%

Ultrathin Microporous Transport Layers: Implications for Low Catalyst Loadings, Thin Membranes, and High Current Density Operation for Proton Exchange Membrane Electrolysis

Schuler,

Weber,

Wrubel

et al. 2024

Advanced Energy Materials

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Porous transport layers (PTL) and their surface properties have the potential to improve the performance of proton exchange membrane water electrolyzers (PEMWE), which is imperative to reduce feedstock costs and lead to their widespread implementation. This work introduces a novel generation of titanium microporous layers (MPLs) with ultra‐low thicknesses of ≈20 µm which reduces raw material costs. They also feature advanced interfacial properties tailored to maximize catalyst utilization at low Ir‐loadings. The bulk morphology and surface properties of the hierarchically structured PTLs are assessed by X‐ray tomographic microscopy. The low surface roughness of the MPL allows the use of thinner membranes since it minimizes possible deformations in the membrane. Cells containing the MPLs outperformed those containing state‐of‐the‐art commercially available PTL materials by up to 100 mV at 7 A cm−2 in combination with low‐loaded catalyst‐coated membranes of 0.4 mgIr cm−2. Hydrogen crossover is also reduced, especially at low current densities, leading to a larger turndown ratio which can enable more cost‐effective operating strategies. Finally, these rationally designed MPLs also lead to high catalyst utilization by overcoming the naturally occurring high in‐plane resistance of low‐loaded catalyst layers.

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Understanding the microstructure of a core–shell anode catalyst layer for polymer electrolyte water electrolysis

Cited by 9 publications

References 42 publications

How the Porous Transport Layer Interface Affects Catalyst Utilization and Performance in Polymer Electrolyte Water Electrolysis

How the Porous Transport Layer Interface Affects Catalyst Utilization and Performance in Polymer Electrolyte Water Electrolysis

A Viewpoint on X-ray Tomography Imaging in Electrocatalysis

Ultrathin Microporous Transport Layers: Implications for Low Catalyst Loadings, Thin Membranes, and High Current Density Operation for Proton Exchange Membrane Electrolysis

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