Hybrid nanocomposites based on the MF-4SK membrane and platinum have been obtained by chemical reduction with sodium borohydride of H(2)[PtCl(6)] in solutions with varying concentration and reaction time. The resulting metal composites have been characterized using standard contact porosimetry and atomic force microscopy techniques and by measuring electric conductivity, permeability, and current-voltage curves. The particle size of metallic platinum has been determined, and the membrane surface roughness factor has been evaluated. Conditions for the preparation of samples with a uniform coating of the membrane surface with a platinum dispersion have been selected. A study of the polarization phenomena has revealed that the parameters of the current-voltage characteristic depend on the orientation of the membrane with respect to proton flux. The presence of platinum on the membrane surface leads to a change in the potential of the transition of the system to the overlimiting state and causes oscillations in the current-voltage curve.