Catalyst coated composite membranes

Abstract

Abstract The introduction of expanding polytetrafluoroethylene (ePTFE) micro‐reinforced composite perfluorosulfonic acid membranes by Gore (Gore‐Select ® membrane) provides numerous benefits for polymer electrolyte membrane fuel cells (PEMFCs). This chapter reviews some of the important physical properties of the membranes such as tear strength, dimensional stability, hydrogen permeability, and resistance as a function of RH, comparing a commercially available nonreinforced membrane and the Gore‐Select ® membrane. The performance of the Primea ® membrane electrode assembly (MEA) Series based on the Gore‐Select ® membrane is discussed and compared to thicker nonreinforced membranes. The reduced thickness of the electrolyte results in an obvious reduction in membrane resistance in the cell, but also provides increased membrane hydration uniformity as a result of the rapid water back diffusion. The combination of these factors provides improved power density, as well as the ability to operate fuel cell systems with sub‐saturated reactant streams and at higher temperatures. Fuel cell test results for a series of reinforced and nonreinforced membranes, along with ex‐situ analysis, provides insight into predominant membrane failure mechanisms in PEMFCs. Thin reinforced membranes have been found to have significantly longer life than much thicker nonreinforced membranes, supporting the conclusion that mechanical properties of membranes maybe more important than their intrinsic chemical properties in dictating membrane life. This chapter discusses the economic aspects of Gore‐Select ® composite membranes compared to commercially available pure‐film membranes, including the combined benefits of increased performance and decreased ionomer content.