Breakthrough in Fuel Cell Research: Graded Roll-to-Roll Slot Die Coating Accelerates Catalyst Development
Fuel cells are a crucial part of the transition toward renewable energy, particularly proton exchange membrane fuel cells (PEMFCs). One of the primary challenges in PEMFC development is optimizing the catalyst layer composition, which historically requires multiple coating experiments to fine-tune material properties. A new study, titled Graded Roll‐to‐Roll Slot Die Coating for High‐Throughput Catalyst Layer Studies published in ChemElectroChem, introduces a more efficient method using a tabletop roll-to-roll (R2R) slot die coater to create graded catalyst layers in a single experiment. The study, which utilized the LR2RC1500 from infinityPV, demonstrates how this technique can streamline catalyst layer research, reducing time and material waste.
Key Highlights
A tabletop Laboratory Roll-to-Roll Coater (LR2RC1500) from infinityPV was used to produce graded catalyst layers in a single experiment.
The study focused on varying platinum loading in PEMFC cathodes by adjusting the wet film thickness during the coating process.
In-line confocal sensors measured the wet film thickness, with area X-ray fluorescence (XRF) scans providing additional validation.
The method successfully created a continuous gradient of platinum loadings, eliminating the need for multiple discrete coatings.
Electrochemical performance testing confirmed that results align with previous findings on catalyst layer optimization.
The process enables faster, more cost-effective material screening for fuel cell research and beyond.
Future applications could extend this approach to other electrochemical systems, such as PEM water electrolysis.
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Experimental Methodology
Coating Process
The researchers used a Laboratory Roll-to-Roll Coater from infinityPV to coat a 100 µm thick PTFE foil with a platinum-based catalyst ink. The slot die head had a coating width of 50 mm, and the coating gap was set at 150 µm. The ink flow rate was systematically reduced from 0.85 ml/min to 0 ml/min over six minutes, producing a linear gradient in film thickness.
Measurement Techniques
To ensure accuracy, the researchers employed:
Confocal sensors (Keyence CL-3000) for in-line wet film thickness measurement.
X-ray fluorescence (XRF) scans to assess platinum distribution.
Scanning electron microscopy (SEM) for structural analysis of the catalyst layer.
Electrochemical testing using a Scribner 850e test station to evaluate cell performance.
Results and Discussion
Relationship Between Film Thickness and Catalyst Loading
A direct correlation was observed between wet film thickness, XRF platinum intensity, and catalyst loading. The platinum loading ranged from slightly over 0.3 mgPt/cm² to below 0.1 mgPt/cm². This gradient method offers a precise and efficient approach to studying catalyst layer properties without requiring multiple coatings.
Electrochemical Performance
Three different cathode loadings were tested in a PEMFC, demonstrating that increasing platinum loading enhances performance but with diminishing returns. The transition from 0.1 mgPt/cm² to 0.2 mgPt/cm² resulted in significant improvements, while the shift from 0.2 mgPt/cm² to 0.3 mgPt/cm² showed only marginal gains. These findings align with previous studies on PEMFC catalyst optimization.
At lower platinum loadings, mass transport limitations affect fuel cell performance. As loading increases, these limitations diminish, improving efficiency. However, beyond a certain threshold, additional platinum does not significantly enhance performance, emphasizing the need for optimized material use.
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Future Applications
The study establishes a foundation for further research into gradient catalyst layers. Potential applications include:
High-throughput screening of new catalyst materials.
Fuel cell stack performance improvements using in-plane gradient structures.
Application in other electrochemical systems, such as PEM water electrolysis and alkaline fuel cells.
More efficient screening of novel catalyst formulations.
Industrial-scale roll-to-roll implementation for commercial PEMFC production.
Conclusion
This study successfully demonstrates the capabilities of roll-to-roll slot die coating as a high-throughput method for producing graded catalyst layers in electrochemical systems. By varying the volume flow into the slot die head, the researchers manufactured a wet film graded catalyst layer for PEMFCs, allowing for systematic performance testing with different catalyst loadings. The wet film thickness was measured in-line, and the correlation between XRF Pt intensity, gravimetric loading, and fuel cell performance was confirmed.
The results reinforce the effectiveness of this approach for screening catalyst loadings in a single experiment, significantly reducing time and material waste compared to traditional methods. The setup provides a robust and scalable solution for optimizing catalyst layers, not only for fuel cells but for other electrochemical applications.
Future advancements in this method will focus on expanding its capabilities, including dual-ink experiments for studying the ionomer-to-carbon (I/C) ratio in a single graded coating. Additionally, the approach could be adapted for stack-level performance improvements by integrating graded catalyst layers directly into catalyst-coated membranes (CCMs). Further refinements in ink behavior during coating and enhanced XRF calibration will be essential to maximize the accuracy and applicability of this technique in industrial settings.
By leveraging the Laboratory Roll-to-Roll Coater from infinityPV, this research sets a new standard for high-throughput catalyst layer optimization, making fuel cell development faster, more precise, and more scalable than ever before.
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