WATER-UPTAKE BY AND TRANSPORT THROUGH NAFION(R) 117 MEMBRANES

Water uptake and transport properties of Nation((R) a) 117 membranes a t 30-degrees-C are reported here. Specifically, we have determined the amount of water taken up by membranes immersed in liquid water and by membranes exposed to water vapor of variable water activity. Transpor t parameters measured are the diffusion coefficient and relaxation tim e of water in the membrane and the protonic conductivity of the membra ne as functions of membrane water content. The ratio of water molecule s carried across the membrane per proton transported, the electro-osmo tic drag coefficient, also was determined for a limited number of memb rane water contents. The drag coefficient is contrasted with the exper imentally determined net water transport across an operating PEM fuel cell.