A mathematical model is proposed for the counter-current diffusion of hexachloroplatinic acid in perfluorinated Nafion membranes using sodium borohydride as a reducer. The model equations are employed to describe the metallic platinum (Pt) concentration profiles across the membrane. Diffusivities are obtained from permeation measurements and then the theoretical data are compared with experimental results which are obtained by electron dispersive microanalysis spectroscopy. There is a good agreement between the simulated model equation and the experimental results. It is expected that this model can provide an idea of the development of the new Pt-solid-polymer-electrolyte (Pt-SPE) electrode.