Nano-Materials to Control Two-Phase Transport in PEM Fuel Cell Electrodes

Under high current density operation excessive liquid water generation in the cathode by electro-osmotic drag and the oxygen reduction reaction often leads to high liquid water saturation level or flooding condition in the cathode catalyst layer. This condition is exacerbated when a hydrophobic micro-porous support layer is incorporated between the catalyst layer and the macro-porous gas diffusion layer. To provide and maintain reactant gas access to the reactive sites under high liquid water saturation level or flooding condition hydrophobic nano-particles are incorporated into the catalyst layer. These nano-particles when properly placed in the void space between the NafionŽ-coated catalyst agglomerates provide continuous pathways for both gas and liquid water transport in the catalyst layer. This presentation will discuss the preparation approach used and catalyst compositions needed to achieve this multi-phase transport structure while maintaining optimal ionic and electronic conductivity in the catalyst layer. >