Adsorption of water vapor on a polymer electrolyte membrane

Adsorption isotherm of water vapor on a sulfonated polyethersulfone (S-PES) membrane in the temperature range from 10 to 50 ∘ C is measured in the present study. The sigmoid curve isotherm that we proposed for the adsorption of water vapor on Flemion ® and Nafion ® is also applied to that of S-PES similarly. The obtained adsorption isotherm shows that varieties of the amount of water adsorbed in the S-PES with temperature is smaller than those of Flemion ® and Nafion ® . Thus, varieties of the proton conductivity of the S-PES membrane with temperature is larger than that of Flemion ® and Nafion ® , because the proton conductivity in those electrolyte membranes depends on the amount of water in them.