Nafion‐Based Membranes for Proton Exchange Membrane Fuel Cells

Proton exchange membrane fuel cells are devices that directly convert the chemical energy of a chemical reaction into electrical energy in the form of direct current. This device has characteristics that position itself as a promising source of clean energy. An essential component that directly affects the performance of fuel cells is the membrane used as electrolyte. In order to improve its efficiency, the membrane should be designed to comply with specific requirements such as high proton transport, good electrical insulation, low fuel permeability, and excellent thermal and chemical stability, to name only the most relevant elements. One of the most widely used and researched materials is the Nafion membrane, a hydrophobic fluoropolymer that contains hydrophilic side chains or ramifications ended in sulfonic acid group (−SO 3 H). Throughout this chapter, the properties of Nafion and specifically its relevant structural and transport models were analyzed in detail. In this sense, small-angle X-ray/neutron spectroscopy (SAXS-SANS) are mandatory supplements and powerful tools for characterizing Nafion membranes and allow us to understand the fuel cell performance and how they are modified when subjected to different stimuli. In addition, results from different studies and authors are summarized.