Proton Exchange Membrane

Raising the operating temperature of proton exchange membrane fuel cells (PEMFCs) offers numerous advantages, such as accelerating electrode reactions, enhancing platinum catalyst tolerance to CO, and simplifying water and thermal management. However, high-temperature PEMFCs impose stricter requirements on the thermal stability and proton conductivity of proton exchange membranes under low-humidity conditions. Modified perfluorosulfonic acid (PFSA) membranes exhibit poor thermal stability and cannot be used under true high-temperature conditions; organic/inorganic composite membranes and non-aqueous proton solvent membranes represent promising directions for high-temperature proton exchange membranes—especially phosphoric acid-doped polybenzimidazole (PBI) membranes. Polybenzimidazole (PBI) and its derivatives are semi-crystalline polymers with high Young’s modulus, excellent thermal decomposition resistance, and outstanding oxidative, acidic, and alkaline stability. After phosphoric acid doping, PBI membranes meet the mechanical strength requirements for fuel cells and are widely studied as high-temperature proton exchange membrane materials. Industry Chain The production of perfluorinated proton exchange membranes requires raw materials including sulfonic acid-functionalized perfluoro vinyl ether monomers and tetrafluoroethylene, which undergo copolymerization to yield perfluorosulfonic acid resin, subsequently processed into perfluorinated proton exchange membranes. The technology for manufacturing PFSA resin—used in proton exchange membranes—is highly demanding, requiring substantial technical expertise and experience in raw material selection and synthesis processes. Major global producers of PFSA resin include DuPont (U.S.), 3M (U.S.), W. L. Gore & Associates (U.S.), Solvay (Belgium), and Asahi Kasei (Japan). In China, Dongyue Group and Kerun are the main domestic manufacturers of PFSA resin; other companies with R&D projects underway include Shanghai San’ai Fu and Juhua Group—but their capacities remain small. As of 2020, Chemours (originally DuPont), Solvay, and Asahi Kasei collectively accounted for over 90% of global PFSA resin capacity, while China’s import dependency on PFSA resin stood as high as 99%. Among domestic companies, Dongyue Group has progressed most rapidly. In 2004, Dongyue Group collaborated with Shanghai Jiao Tong University to develop a proton exchange membrane matching international performance benchmarks. Between 2014 and 2016, Dongyue’s membrane lifetime increased from 800 hours to 6,000 hours; its DF260 membrane has matured and entered mass production. Dongyue’s planned industrialization project—a 1.5-million-square-meter annual capacity for fuel cell membranes and associated chemicals—is under construction, including a dedicated PFSA resin production facility with an annual capacity of 50 tons of ion-exchange membranes. Phase I (500,000 m²) commenced operations in 2021. Jiangsu Kerun has achieved small-batch supply of proton exchange membranes and currently operates two perfluorinated ion-exchange membrane production lines, with a total capacity of 300,000 m²/year. Wuhan Lvdon Hydrogen Energy—a subsidiary of State Power Investment Corporation—has completed a 300,000 m²/year proton exchange membrane production line capable of manufacturing membranes ranging from 8 to 20 micrometers in thickness. Additionally, companies including Zhejiang Hancheng and Dongguan Materials Science & Technology have announced or initiated projects targeting annual capacities exceeding 300,000 m². Through sustained R&D investment, these enterprises have pioneered domestic production of proton exchange membranes and are expected to gain first-mover advantages in industry competition. Currently, domestically produced proton exchange membranes primarily compete by actively lowering prices. If full localization is achieved, membrane prices are projected to decline by 30–40%.

From 'Ionic Clusters' to Market Scale: Why Is This Material—Ionomer—Worth Watching?

1. Introduction to Perfluorosulfonic Acid (PFSA) Ionomers Perfluorosulfonic acid (PFSA) ionomers are a class of ion-conducting polymers renowned for their exceptional ion conductivity and chemical–mechanical stability. PFSA ionomers are commonly employed as solid electrolytes in electrochemical technologies—particularly as proton exchange membranes in polymer electrolyte fuel cells and as sodium-ion conductors in chlor-alkali electrolysis. In the 1970s, DuPont developed the first commercially viable PFSA ionomer monomer, Nafion®. DuPont’s Nafion® membrane—a commercially available PFSA-based membrane—is widely used in fuel cell applications. Even after decades of research, Nafion® remains the benchmark solid electrolyte for most energy storage and conversion devices due to its intrinsic electrochemical functionality: it enables efficient ion and solvent transport within a chemically inert, mechanically robust matrix, while effectively suppressing electron conduction and crossover of reactants/products. Nafion® is a random copolymer composed of an electrically neutral, semi-crystalline polymer backbone (polytetrafluoroethylene, PTFE) and randomly distributed side chains bearing pendant ionic groups (sulfonated sulfonyl fluoride vinyl ether), each associated with a counterion (e.g., SO₃⁻ + H⁺ → SO₃H). The covalently attached ionic side chains and the hydrophobic backbone possess markedly different properties, leading to intrinsic phase separation—which is further enhanced upon solvation (e.g., by water or other solvents). This phase-separated morphology endows PFSA ionomers with their unique ion and solvent transport capabilities. Thus, PFSA ionomers are intrinsically multifunctional polymers whose transport and mechanical properties are governed by morphology, which itself arises from electrostatic interactions. Yet this morphology also reflects a delicate balance among various competing energies: mechanical (deformation) energy associated with the hydrophobic backbone, and chemical/entropic energy linked to hydration of the hydrophilic ionic groups and their side chains. 2. Major Producers and Products of PFSA Ionomers Currently, major global producers of PFSA ionomers include Chemours, Solvay, Asahi Kasei, and Fluorochemie. Chemours’ PFSA ionomer business originated from DuPont’s spin-off: in July 2015, DuPont transferred its ‘High Performance Chemicals’ business—including the PFSA ionomer program—to the newly established Chemours Company. Its Nafion™ PFSA membranes, based on PFSA/PTFE copolymers, serve as cation-conducting solid electrolytes in electrochemical cells. Solvay produces several PFSA ionomer products, including Aquivion® D79-25BS, Aquivion® D72-25BS, and Aquivion® E98-05. These feature high crystallinity, improved mechanical properties, and superior proton conductivity, and are primarily used in fuel cell electrodes and electrochemical cell electrodes. Asahi Kasei is one of the world’s leading PFSA ionomer producers. Its PFSA ionomer product lines—Aciplex® and Flemion®—are mainly applied in high-performance fields such as proton exchange membrane fuel cells.

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