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