Nafion 117 is a perfluorosulfonic acid (PFSA) proton exchange membrane that conducts protons (H⁺) and other cations while separating the anode and cathode. It is extrusion-cast, nominally 183 µm (7 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 117 is the thickest Nafion in this group. As the option that best limits methanol, vanadium-ion or gas crossover, it suits direct methanol fuel cells (DMFC), flow batteries and H-type cell experiments; in return its ionic resistance is higher than that of 115, 212 and 211.

Key Features

Nominal thickness 183 µm (7 mil), basis weight 360 g/m² (manufacturer data)
Extrusion-cast PFSA membrane in the acid (H⁺) form
Conductivity at least 0.10 S/cm; available acid capacity at least 0.90 meq/g (manufacturer data)
Thickest Nafion in this group: best crossover barrier, highest resistance
Swells about 10% (23 °C) to 15% (100 °C) when wet; allow for this in gaskets and cutting size
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

Membrane type	Proton (cation) exchange membrane, PFSA
Production method	Extrusion-cast
Nominal thickness	183 µm (7 mil)
Basis weight	360 g/m² (manufacturer data)
Conductivity	At least 0.10 S/cm (manufacturer data)
Acid capacity	Available at least 0.90 meq/g; total 0.95–1.01 meq/g
Water uptake	38% (dry to water at 100 °C, 1 h; manufacturer data)
Wet expansion	Linear, about 10% (23 °C) – 15% (100 °C)
Tensile strength	43 / 32 MPa (MD / TD, 50% RH, 23 °C)
Operating temperature	Conductivity falls if it dries out above about 80 °C
Form	Acid (H⁺) form (manufacturer data)
Size	100 × 100 mm