Designing catalyst layer morphology for high-performance water electrolysis using synchrotron X-ray nanotomography

Lee, Jason K.; Kim, Pascal; Krause, Kevin M.; Shrestha, Pranay; Balakrishnan, Manojkumar; Fahy, Kieran F.; Fatih, Khalid; Shaigan, Nima; Ge, Mingyuan; Lee, Ivan; Bazylak, Aimy

doi:10.1016/j.xcrp.2022.101232

Cited by 16 publications

(11 citation statements)

References 35 publications

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“…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%

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: 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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“…To aid these efforts, more smaller-scale characterisation should be done, using techniques such as nano-CT 70 or FIB-SEM. 32 Nano-CT in conjunction with pore network modelling (PNM) is a method proposed by Lee et al 70 that can help in understanding how different ink compositions affect structural properties in the CL (e.g., how varying the I/C ratio would impact pore size distribution). FIB-SEM analysis on a blade coated Pt-Ir CL conducted by Peng et al suggests that tortuosity can significantly affect mass transport, demonstrating that nanostructural properties of the CL (in this case, the nanostructure was a 'nano-pattern') can significantly impact performance.…”

Section: Ink Fabricationmentioning

confidence: 99%

“…Therefore, finding ink rheologies that grant uniform coatings will be necessary to achieve durable and active ultra-low-loading CLs. To aid these efforts, more smaller-scale characterisation should be done, using techniques such as nano-CT 70 or FIB-SEM. 32 Nano-CT in conjunction with pore network modelling (PNM) is a method proposed by Lee et al 70 that can help in understanding how different ink compositions affect structural properties in the CL (e.g., how varying the I/C ratio would impact pore size distribution).…”

Section: Ink Fabricationmentioning

confidence: 99%

Design of PEM water electrolysers with low iridium loading

Wang,

Lee,

Liu

et al. 2024

International Materials Reviews

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To enable gigawatt-scale deployment of proton exchange membrane water electrolysers (PEMWEs), drastic reductions from current iridium loadings of 2–3 mgIr cm−2 to less than 0.4 mgIr cm−2 must occur due to iridium's high cost and scarcity. State-of-the-art systems use these high loadings to compensate for degradation experienced over prolonged operation. Thus, to attain low loadings while meeting commercial lifetime targets, factors such as ink formulation, MEA fabrication, catalyst layer–porous transport layer (CL–PTL) contact, and catalyst durability must be optimised. This review paper discusses the fundamentals of PEMWE technology and the modifications/improvements necessary for effective low iridium-loading design. Important milestones for future research include developing durable catalyst layers at low loadings, optimising the CL–PTL interface, and improving roll-to-roll production processes.

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“…[17][18][19] Several studies in recent literature have addressed the impact of PTLs on PEMWE. [20][21][22][23][24] Schuler et al correlated PTL bulk and surface characteristics to overpotentials. In their work, surface properties, such as the interfacial contact area, were identified as key performance indicators in particular for CL utilization.…”

Section: Introductionmentioning

confidence: 99%

“…Several studies in recent literature have addressed the impact of PTLs on PEMWE. [ 20–24 ] Schuler et al. correlated PTL bulk and surface characteristics to overpotentials.…”

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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Designing catalyst layer morphology for high-performance water electrolysis using synchrotron X-ray nanotomography

Cited by 16 publications

References 35 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

Design of PEM water electrolysers with low iridium loading

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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