Water Uptake by and Transport Through Nafion® 117 Membranes

Abstract

LIST OF SYMBOLS C~ ~the maximum adsorption sites on the electrode surface C~+ the concentration of adsorbed proton, H~+d in Eq. 1 CH, CHC, CHCm C~2 the concentration of adsorbed H~d in Eq. 4, HCOQd in Eq. 5, HCOOH in Eq. 6, and H2 in Eq. 20 Cp, Cco2 the concentration of H~ol and CO2 in solution kE, ko, kDES, kH2 the rate constant for reactions of Eq. 4, 5, 6, and 20, respectively %, ~DES the time constant defined by Eq. 9 and 12, respectively V~, V ~ the formal potential for Eq. 1 and 17

Mechanics-based model for non-affine swelling in perfluorosulfonic acid (PFSA) membranes

“…However, at higher water activities, the spherical and the cylin drical RVEs diverge, and the experimental data seem to shift from the S-RVE predictions at intermediate activity (0.5 < a w < 0.8) to the C-RVE predictions at higher activities (a w > 0.8). A similar shift has been observed in experimental sorption data of PFSA membranes at around a w ¼ 0.7-0.8 [8]. They attribute the region with lower slope with the solvation of SO 3 3 ions with water, and the region with higher slope to the swelling of the membrane with additional free water [8].…”

“…The resulting sorption isotherms are depicted in Fig. 6 along with experimental data for the water uptake of EW 1100 membranes from Zawod zinski et al [8,38], Morris and Sun [10], Choi et al [42], and the [42] and the empirical models from Springer et al [6] and Thampan et al [44].…”

“…Upon water uptake, 3 water molecules initially ionize the SO 3 groups and remain bound to them. Additional water molecules are then free to move through the ionomer, causing growth of the clusters and consequently the macroscopic swelling of the membrane [8,9,11,24,34,[38][39][40][41].…”

“…This relationship is referred to as non-affine deformation and has been shown to occur for PFSA membranes by a number of studies in literature [11,[18][19][20][21][22]29,[33][34][35]. Despite the growing body of literature on the sorption behavior [7,8,10,24,34,35,38,40,[44][45][46][47][48][49][50] and nano-structural modeling and characterization [11,13,[17][18][19][20][21][22]28,29,31,[33][34][35][36]39,49,51,52] of PFSA ionomers, the relationship between the water uptake and nanostructure, temperature, mechanical properties and membrane pretreatment is not well established. Understanding of these issues requires a general, yet fundamental model, which is the subject of this study.…”

Non-fluorinated proton-exchange membranes based on melt extruded SEBS/HDPE blends

“…The ionic exchange capacity was decreased significantly with HDPE content especially at the lower functionalization time of 60 min. The IEC of s-SEBS was in [40] n/a 1.00E−02 the 1.8-1.9 meq g −1 range and did not increase much with sulfonation time. The blends however largely benefited from the increased treatment time.…”