  A Devanathan-Stachurski type diffusion cell made from a fuel cell assembly is
designed to evaluate the gas transport properties of a proton exchange membrane
as a function of cell temperature and gas pressure. Data obtained on this cell
using the electrochemical monitoring technique (EMT) is used to estimate
solubility and diffusion coefficient of oxygen (O2), carbon monoxide (CO) and
hydrogen sulfide (H2S) in Nafion membranes. Membrane swelling and reverse-gas
diffusion due to water flux are accounted for in the parameter estimation
procedure. Permeability of all three gases was found to increase with
temperature. The estimated activation energies for O2, CO and H2S diffusion in
Nafion 112 are 12.58, 20 and 8.85 kJ mol^-1, respectively. The estimated
enthalpies of mixing for O2, CO and H2S in Nafion 112 are 5.88, 3.74 and 7.61
kJ mol^-1, respectively. An extensive comparison of transport properties
estimated in this study to those reported in the literature suggests good
agreement. Oxygen permeability in Nafion 117 was measured as a function of gas
pressures between 1 and 3 atm. Oxygen diffusion coefficient in Nafion 117 is
invariant with pressure and the solubility increases with pressure and obeys
Henry's law. The estimated Henry's constant is 3.5 x 10^3 atm.
