A Cleaner, Tunable Alternative for Hydrogen Fuel Cells and Water Electrolyzers Hydrogen energy systems depend on a small but critical polymer layer inside each electrode, called an ionomeric binder, that shuttles protons, manages water and lets reactant gases reach the catalyst. The industry has long relied on perfluorosulfonic acid (PFSA) materials for this role, which contain PFAS (per‑ and polyfluoroalkyl substances) — “forever chemicals” — now under increasing regulatory pressure. Researchers at Los Alamos National Laboratory have developed a family of highly sulfonated poly(norbornene) ionomers that are entirely PFAS-free, deliver strong proton conductivity, do not poison precious-metal catalysts the way conventional aromatic alternatives do, and can be chemically tuned to keep electrodes dry under load. Together, these qualities position the material as a drop-in path forward for high-performance proton exchange membrane (PEM) fuel cells and water electrolyzers in a tightening environmental landscape. How it Works PFAS-Free Sulfonated Poly(norbornene) Ionomeric Binders are a class of aliphatic sulfonated poly(norbornene) polymers designed specifically as electrode ionomers in proton-conducting devices. The polymer's backbone is built from fused bicyclic norbornane units that lack the aromatic pi-electron systems found in conventional hydrocarbon ionomers. The absence of those electrons means the polymer does not strongly adsorb onto platinum catalyst surfaces, so catalytic activity is preserved. Sulfonic acid groups covalently attached onto this backbone supply the proton-conducting pathways, while the bulky bicyclic rings create extra free volume inside the polymer, allowing oxygen and hydrogen to diffuse more easily through the binder layer and reach the catalyst. By adjusting the ratio of sulfonated to non-sulfonated segments, the developers can dial in ionic activity and hydrophobicity to prevent electrode flooding, a persistent issue for PFAS-free ionomers when operated at high current density. Technology Description In a PEM fuel cell or water electrolyzer, the membrane electrode assembly (MEA) is the heart of the device, and the electrode ionomer inside it must simultaneously conduct protons, transport water, allow reactant gases to reach catalyst particles and bind mechanically to both the membrane and the catalyst layer. PFSA materials such as Nafion meet these requirements but carry the environmental burden associated with perfluorinated chemistries. Hydrocarbon-based sulfonated polymers offer a cleaner, lower-cost route, yet their phenyl-rich backbones tend to adsorb onto platinum and reduce catalytic activity, their gas permeability is typically low and the high sulfonic acid content needed for conductivity drives down hydrophobicity, leading to flooding under realistic operating conditions. PFAS-Free Sulfonated Poly(norbornene) Ionomeric Binders target each of these failure modes simultaneously by replacing the phenyl-heavy arc…