4.6 CHAPTER SUMMARY
This chapter provides an overview of water and proton transports that occur in the polymer electrolyte membrane and catalyst layers of a PEM fuel cell.
The key points of this chapter are summarized as follows:
• Ionic or protonic conductivity is the most important property of polymer electrolyte membranes and directly determines the ohmic voltage loss. Several protonic conductivity correlations are discussed and compared; a constitutive model of protonic conductivity is derived from ion transport fundamentals; and an experimental method of measuring membrane ionic conductivity is described.
• Membrane water content strongly affects the protonic conductivity and water diffusivity, which are essential to achieving and maintaining ...