Slot-die-coating operability windows for polymer electrolyte membrane fuel cell cathode catalyst layers

Area of Science:

• Materials Science
• Chemical Engineering
• Electrochemistry

Background:

• Roll-to-roll (R2R) slot-die coating is a scalable method for producing polymer electrolyte membrane fuel cell (PEMFC) catalyst layers.
• High-throughput production is crucial for reducing PEMFC costs, targeting the U.S. DOE's $30/kW$_{net}$ goal.
• Ink concentration significantly impacts the process parameters required for uniform, defect-free coatings.

Purpose of the Study:

• To experimentally and theoretically explore the defect-free coating parameter window for PEMFC cathode inks at different concentrations.
• To develop and validate predictive models for slot-die coating processes.
• To demonstrate a pathway for cost reduction in PEMFC manufacturing.

Main Methods:

• Utilized roll-to-roll slot-die coating technique.
• Investigated two ink concentrations (5.3 wt% and 12.0 wt% solids).
• Employed both a full capillary hydrodynamic model and a viscocapillary model for prediction.

Main Results:

• Both hydrodynamic and viscocapillary models accurately predicted the experimentally determined defect-free coating windows for both ink concentrations.
• Achieved the target platinum (Pt) areal loading of 0.1 mg$_{Pt}$·cm^-2.
• Concentrated inks require higher vacuum levels but offer reduced drying energy and capital expenditure.

Conclusions:

• Predictive modeling provides a viable pathway to identify optimal slot-die coating parameters, minimizing material waste.
• The use of concentrated inks in slot-die coating is a promising strategy for cost-effective PEMFC production.
• This approach supports the U.S. DOE's cost reduction targets for hydrogen fuel cell technologies.