PREPARATION OF SOLID POLYMER ELECTROLYTE COMPOSITES - INVESTIGATION OF THE ION-EXCHANGE PROCESS

The rate of ion-exchange between an aqueous solution of platinum tetra mine and a Nafion(R) 117 membrane in H+ form is studied. Experimental data are collected using extended X-ray absorption fine structure (EXA FS) spectroscopy in dispersive mode. Results are obtained for various platinum tetramine concentrations in the solution and different hydrod ynamic regimes at the membrane-solution interface. A shift from a laye r diffusion controlled rate (L) to a membrane diffusion controlled rat e (M) is observed when the salt concentration and the stirring of the solution are increased. Time dependent fractional concentration in pla tinum tetramine inside the membrane are computed for the two limiting cases of diffusion (L and M). Good agreement is found between experime ntal and simulated data. The role of the rate of ion-exchange on the e lectrochemical performances of electrode-membrane-electrode composites for water electrolysis applications is discussed.