Optimized Catalyst Layer Structure for PEM Fuel Cells

Abstract

The optimal operating conditions for PEM fuel cells for high durability and performance are near water saturated conditions. Under these conditions liquid water exists in the catalyst layers of the anode and cathode. When the accumulation of water is excessive it can lead to electrode flooding, which reduces the performance of the fuel cells, by flooding the gas pores needed for active gas transport and forming an additional liquid water film barrier over the active sites. Consequently, to reduce the effect of electrode flooding of the catalyst layers the structure of the catalyst layer must be modified to enable fast gas and liquid water transport. Furthermore, this must be achieved without resulting in any significant loss in the ionic and electronic conductivity of the catalyst layer. This work presents two approaches developed to achieve this goal. The first approach explores the concept of creating a four phase (electronic, ionic, gas and liquid) simultaneously. The second approach explores the concept of first creating a three-phase (electronic, ionic and gas) structure and then modifying the gas structure to provide simultaneous but separate gas and liquid transport paths. The results show the second approach to be more optimal.