Transport Properties of MF-4SK Perfluorinated Membranes Modified with Zirconium Hydrogen Phosphate

The physicochemical and transport characteristics of cast and extruded MF-4SK perfluorinated membranes modified with zirconium hydrogen phosphate in an amount of 3–10% are studied. The inorganic phase is formed directly in the membrane volume by the pore-filling method. The effect of zirconium hydrogen phosphate content on the ion-exchange capacity, water content, diffusion permeability for electrolyte solution, hydrogen gas permeability, and electrical conductivity at the limited humidity of the MF-4SK membrane, as well as the efficiency of its use in a low-temperature proton-exchange membrane fuel cell, are investigated. A nonmonotonic change in the transport characteristics depending on the dopant content is demonstrated. The lowest diffusion permeability and maximum electrical conductivity at low humidity are exhibited by the membrane containing 6% of zirconium hydrogen phosphate. It is shown that zirconium hydrogen phosphate-modified membranes show promise as a polymer electrolyte in a hydrogen-air fuel cell membrane-electrode assembly due to a 17% higher maximum specific power compared to the original MF‑4SK membrane. This fact can be explained by an almost twofold lower ohmic resistance and reduced contribution of kinetic limitations of the membrane-electrode assembly (MEA) with the modified membranes, compared to the unmodified membrane, revealed by analysis of its impedance spectra.