Designing Electrodes with No Ionomers: A Perspective on Ionomer-Free Electrodes for Proton-Exchange-Membrane Water Electrolyzers

Proton-exchange-membrane water electrolyzer (PEMWE) is a promising technology for producing clean hydrogen as it offers high current operation, compact design, and ability to operate with intermittent renewable energy. However, high costs related to platinum group metal (PGM) usage and titanium components pose a bottleneck in further scale-up of PEMWEs. This perspective introduces an ionomer-free PEMWE system as a viable approach to facilitate scale-up and cost reduction of PEMWEs. In conventional PEMWEs, ionomers serve as binders for the electrodes as well as a medium to conduct protons. However, most ionomers used in PEMWEs rely on perfluoroalkyl and polyfluoroalkyl substances, which complicate the manufacturing processes of the catalyst layers and cause a potential concern to the environment. Shifting to ionomer-free electrodes alleviates these challenges and simplifies scale-up processes; however, the application of ionomer-free electrodes remains at an early stage of research, and this perspective provides a guidance on the future direction based on previous research endeavors conducted in the field.