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. 7.8 x 10(-2) S cm(-1) 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 degrees C, its conductivity at a given relative humidity decreased with increasing temperature, while from 45 to 80 degrees C it increased with temperature.