The Effects of Catalyst Layer Composition onthe Polymer Electrolyte Membrane (PEM) Fuel Cell Performance: (I) Modeling

Abstract

The optimisation problem for the PEM fuel cell catalyst layer was investigated by using the concept of percolation theory. The present work aims to introduce a simple model exploring the effect of catalyst layer composition parameters on the catalyst layer performance. Four design parameters were involved in this study, the Nafion ionomer volume fraction, the pores volume fraction, the catalyst loading and the catalyst layer thickness. Based on the modelling results, it can be concluded that the catalyst layer performance depends highly on the Nafion volume fraction, the pore volume fraction, and the catalyst layer thickness. It was observed that when the Nafion volume fraction approaches to the pore volume fraction, the corresponding catalyst layer thickness is the optimum thickness and the maximum catalyst layer performance was observed. This finding is enhanced by the numerical results, as example, the optimum gemetrical parameters for catalyst layer containing 5.4 mg/cm2 palladium catalyst loading and 27 µm catalyst thickness, are 0.49 Catalyst Volume Fraction, 0.27 Nafion Volume Fraction, and 0.24 Pores Volume Fraction. Moreover, the catalyst layer thickness is dependent on the catalyst loading; with increase in the catalyst loading the thickness should be increased in order to keep the equality between the pore volume fraction and the Nafion volume fraction