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

Abstract 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.