Nafion 211 (NR211) Proton Exchange Membrane

Nafion 211 (maker code NR211) is a thin perfluorosulfonic acid (PFSA) proton exchange membrane that conducts protons (H⁺) and other cations while separating the anode and cathode. It is solution-cast, nominally 25.4 µm (1 mil) thick, and supplied as a 100 × 100 mm sheet.

Thickness is a trade-off in the Nafion family: thin grades (212: 50.8 µm, 211: 25.4 µm) have lower resistance but are more delicate and allow more gas/fuel crossover; thick grades (115: 127 µm, 117: 183 µm) are more robust and limit crossover better, at higher ionic resistance. Nafion 211 is the thinnest membrane in this group: it has the lowest ionic resistance and suits fuel cell work aimed at high power density. In return it is the most delicate, and the maker's hydrogen crossover limit is twice that of Nafion 212. Handle it with care.

Key Features

• Nominal thickness 25.4 µm (1 mil), basis weight 50 g/m² (manufacturer data)
• Solution (dispersion) cast PFSA membrane in the acid (H⁺) form
• Thinnest Nafion in this group: lowest resistance, highest crossover and lowest mechanical strength
• Hydrogen crossover below 0.020 mL/min·cm² (manufacturer data)
• Linear swelling about 10% (23 °C) to 15% (100 °C) when wet; allow for this in MEA gasket design
• Common pretreatment: boiling in 3% H₂O₂ and in 0.5 M H₂SO₄, rinsing with pure water after each step (protocols vary by application)
• 100 × 100 mm sheet; can be cut to size

Technical Specifications

Applications

• PEM fuel cell MEA studies (high power density)
• PEM water electrolysis research
• Redox flow batteries
• Thin-membrane cell designs needing low internal resistance