Fully Hydrocarbon Membrane Electrode Assemblies for Proton Exchange Membrane Fuel Cells and Electrolyzers: An Engineering Perspective

Perfluorinated-sulfonic-acid-based ionomers (PFSAs) are still the material of choice for electrochemical energy devices such as proton-exchange membrane fuel cells or water electrolyzers. However, PFSAs show significant drawbacks ranging from a restricted temperature window of operation due to the insufficient thermomechanical stability, high cost, and questionable environmental properties. Recently, novel hydrocarbon-based ionomers have been introduced, which not only have the potential to overcome these limitations, but also for the first time show promising performance, approaching that of PFSA-based fuel cells and electrolyzers. This article summarizes the recent developments in this emerging field with a particular focus on the engineering of membrane-electrode assemblies with hydrocarbon-based polymer electrolytes. In the final part, the necessary key innovations are discussed, which are required for hydrocarbon ionomers to replace PFSAs in fuel cells and electrolyzers in the future.