(139a) Optimization of the Membrane-Electrolyte-Assembly of the PEM Fuel Cell

A procedure aimed at optimizing the design of catalyst layers for high temperature polymer electrolyte membrane (PEM) fuel cells is presented. In developing the methodology the concept of catalyst effectiveness expressed as a function of the Thiele modulus is applied in determining the optimum thickness of a catalyst layer. Three variables that control the catalyst layer performance are the catalyst loading, specific surface area of catalyst particles and the layer thickness. Given any two of the above variables it is possible to determine the third for optimum catalyst performance. The approach is very simple and only accurate for small size fuel cells systems because of the underlying assumptions in the analysis. For large size systems the method offers, at best, qualitative results that are good enough to guide the design of such systems and serve as a good first-step approach to more complex three-dimensional analyses.