Polymer ion-exchange membranes are featured in a variety of modern technologies including separation, concentration and purification of gases and liquids, chemical and electrochemical synthesis, and hydrogen power generation. In addition to transport properties, the strength, elasticity, and chemical stability of such materials are important characteristics for practical applications. Perfluorosulfonic acid (PFSA) membranes are characterized by an optimal combination of these properties. Today, one of the most well-known practical applications of PFSA membranes is the development of fuel cells. Some disadvantages of PFSA membranes, such as low conductivity at low humidity and high temperature limit their application. The approaches to optimization of properties are modification of commercial PFSA membranes and polymers by incorporation of different additive or pretreatment. This review summarizes the approaches to their modification, which will allow the creation of materials with a different set of functional properties, differing in ion transport (first of all proton conductivity) and selectivity, based on commercially available samples. These approaches include the use of different treatment techniques as well as the creation of hybrid materials containing dopant nanoparticles. Modification of the intrapore space of the membrane was shown to be a way of targeting the key functional properties of the membranes.

Data on the water uptake, proton conductivity, diffusion permeability, cation transport selectivity, and mechanical properties of short side chain Aquivion sulfonated perfluoropolymer membranes with...

Nafion is a perfluorosulfonic acid polymer that is most commonly used in proton-exchange membrane fuel cells. The processes of pretreatment and formation of such membranes strongly affect their properties. In this work, dispersions of Nafion in various ionic forms and dispersing liquids (ethylene glycol, N,N-dimethylformamide, N-methyl-2-pyrrolidone and isopropyl alcohol–water mixtures in different ratios) were obtained and studied. Membranes fabricated by casting of the various dispersions were also studied. The effect of the nature of the dispersing liquid and the counterion on the properties of Nafion dispersions, the morphology of the polymer in the dispersions and the characteristics of the membranes obtained from them has been shown. Based on the overall results, it can be concluded that the use of perfluorosulfonic acid dispersions in aprotic polar solvents is advisable for obtaining membranes by the casting procedure. This is because it provides optimal polymer morphology in the dispersion, which leads to the formation of films with good selectivity, mechanical and transport properties. The performed investigations show the relationship between the composition of dispersions, the morphology of the polymer and the properties of the membranes formed from them by the casting procedure.

Perfluorosulfonic acid Nafion membranes are widely used as an electrolyte in electrolysis processes and in fuel cells. Changing the preparation and pretreatment conditions of Nafion membranes allows for the optimization of their properties. In this work, a Nafion-NMP membrane with a higher conductivity than the commercial Nafion^® 212 membrane (11.5 and 8.7 mS∙cm⁻¹ in contact with water at t = 30 °C) and a comparable hydrogen permeability was obtained by casting from a Nafion dispersion in N-methyl-2-pyrrolidone. Since the ion-exchange capacity and the water uptake of these membranes are similar, it can be assumed that the increase in conductivity is the result of optimizing the Nafion-NMP microstructure by improving the connectivity of the pores and channels system. This leads to a 27% increase in the capacity of the membrane electrode assembly with the Nafion-NMP membrane compared to the Nafion^® 212 membrane. Thus, the method of obtaining a Nafion membrane has a great influence on its properties and performance of fuel cells based on them.

Improvement of the chemical stability of hybrid membranes based on perfluorosulfonic acid polymers is necessary to increase the lifetime of fuel cells. This article presents the results of the study of the transport properties and chemical stability of the hybrid Nafion® 212 membranes modified with nanoparticles of hydrated oxides SiO₂, ZrO₂, and TiO₂ by in situ procedure. The influence of the nature of the dopant on the properties of the obtained materials is shown. The chemical degradation of the initial and hybrid membranes has been studied ex situ by treatment with Fenton’s reagent for 240 hours. The stability of materials increases in the series Nafion + SiO₂ < Nafion + ZrO₂ < Nafion < Nafion + TiO₂. For the Nafion + TiO₂ membrane the change in mass as a result of treatment with Fenton’s reagent is two times lower than for the initial Nafion membrane. This reveals an increase in the chemical stability of materials upon the incorporation of TiO₂ nanoparticles due to their ability to bind free radicals. The maximum power of membrane-electrode assembly based on hybrid membranes containing TiO₂ and SiO₂ is higher than that based on Nafion® 212 by 7–10% at RH ~ 100% and t = 65°C.