Polymer Electrolyte Membrane Fuel Cell (PEMFC) Membranes

Abstract

Polymer electrolyte membrane fuel cells (PEMFCs) use an electrolyte that is based on a polymer membrane and has special properties that allow it to conduct protons without letting the passage of electrons or gases. This electrolyte is located between two electrodes. It must have high proton conductivity and be stable at high temperatures and in chemicals. Most of the polymer-based membranes used in PEMFCs operate at low temperatures. The biggest obstacle to getting the best efficiency from a PEMFC operating with reformate gases is CO poisoning. The presence of a certain amount of CO in the environment leads to a significant decrease in the efficiency of the anode catalyst. Operating PEMFC at high temperatures has recently been seen as a way to both overcome this issue and increase the kinetics of the reactions. Therefore, a PEMFC membrane should have good thermal stability and mechanical strength at high temperatures, ideal thickness, high ionic conductivity, low gas permeability, and low cost. PEMFC membranes are classified as either proton exchange membranes (PEMs), in which negative ions are retained at the backbone ends of a polymer mold and this charge is balanced with protons, or as polymer acid complexes (PACs), where a basic polymer is loaded with acidic components. In this chapter, the physical, thermal, and mechanical properties, ion-conducting principles, and characterization methods of cationic PEMFC membranes operating at low and high temperatures will be examined. The addition of different materials in order to improve the properties of the membranes will also be covered in this chapter.