Direct Roll-to-Roll Coating of Catalyst-Coated Membranes for Low-Cost PEM Water Electrolyzers

Low temperature polymer electrolyte membrane (PEM) water electrolysis is a technology capable of producing hydrogen, which has been in the spotlight with the recent worldwide efforts to improve energy system sustainability and security. As the drive toward megawatt-scale hydrogen production intensifies, the production rate of PEM water electrolyzers is becoming an important issue. Catalyst-coated membranes (CCM) are a key component of water electrolyzers. However, existing spray coating and decal transfer methods have several limitations with regards to large-area production of the CCMs, such as, slow production speeds and multiple process steps.

In this talk, high-throughput and large-area CCM production based on roll-to-roll (R2R) slot-die coating of IrO₂ catalyst inks directly onto the membrane will be discussed. In order to minimize phenomena such as swelling and solvent permeation during direct coating of the ink onto the membrane, ink compositions with various catalyst contents, types of organic solvents, and water-to-solvent ratios are investigated. The results show that alcohol-rich inks may lead to improved particle dispersion and wetting onto the substrate, but have shown poor coating qualities (e.g. cracks and high thickness deviation) due to larger ink-membrane interaction and faster drying rate. In-situ results of R2R-processed CCMs using optimized inks will be presented that indicate comparable electrochemical performance to a lab-scale sample fabricated with the standard ultrasonic spray coating technique. Considering that the R2R-processed CCM has achieved a throughput of several hundred times greater than the lab scale sample (on an area/time basis), it is expected that this manufacturing approach can contribute to a significantly reduced capital cost of PEM water electrolyzers.

This work was authored by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding provided by the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Hydrogen and Fuel Cells Technologies Office. The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes.