Proton Conductivity of Nafion 117 as Measured by a Four‐Electrode AC Impedance Method

The proton conductivity of Nafion 117 was measured under various conditions of humidity and temperature using a four‐electrode ac impedance method. The conductivity of this membrane without heat‐treatment was ca. at ambient temperature and 100% relative humidity; it varied strongly with the humidity and heat‐treatment of the membrane. After heat‐treatment, the membrane showed a slight dependence of conductivity on temperature. From 21 to 45°C, its conductivity at a given relative humidity decreased with increasing temperature, while from 45 to 80°C it increased with temperature.