An Overview on Structure and Properties of Nafion Regarding Proton Exchange Membrane Fuel Cell Application

I n this paper, the structure and properties of the proton exchange Nafion membrane are presented as the most commonly used membrane in electrochemical and separation processes. To this end, the family of perfluorosulfonic acid membranes has been introduced, which Nafion is the most important member. Then, the details and challenges of Nafion synthesis as well as its structure and morphology are discussed in the next step. The nomenclature, as well as the equivalent weight characteristic of diverse types of Nafion membranes, is also described. In the following, the molecular weight and factors affecting the performance and properties of Nafion are discussed. The properties and characteristics of Nafion membrane, including water absorption, chemical stability, thermal behavior, mechanical properties, proton conduction as well as governing mechanisms are explained. Finally, the disadvantages of these membranes, including the low performance at high temperatures and low humidity and high cost, are mentioned. The solutions to remove the obstacles are proposed. These strategies are described in two sections: modification of Nafion membranes and the preparation of alternative membranes. A brief look at the applications of Nafion, the preparation methods of the membrane, activation, and maintenance, as well as the commercial Nafion membrane made by DuPont company has been done. Notably, the description of this material is performed by focusing on the application of this membrane in proton exchange membrane fuel cells.