Optimization of oxygen and proton transfer in heterogeneous PEFC catalyst layer by controlling local carbon black aggregate structure

Polymer Electrolyte Fuel Cell costs higher and higher because of platinum for catalyst and it is necessary to reduce the cost to generalize PEFC. Especially, optimization of catalyst layer, which consists of void space, carbon support and ionomer, is effective to increase the performance of cathode oxygen reduction reaction from the view point of mass transfer. And its structure can be controlled by fabrication process. In this study, threedimensional catalyst layer was simulated by numerical analysis, and the relationship between electrode structure and Pt utilization was examined. Moreover, from the results, the effect of catalyst layer fabrication process on cell performance was examined experimentally. As a result, it is found that Pt utilization depends on the carbon black agglomerate structure. Especially, Pt particle inside carbon phase and ionomer deeper could not be worked for the cathode oxygen reduction reaction because the oxygen transfer to Pt surface is not uniform. However carbon black agglomerate leads to make large pore space and it increase oxygen diffusion rate in the direction of through plane. From this knowledge, optimal electrode structure with carbon black core was designed to improve Pt utilization and oxygen diffusion rate, and the effectiveness was evaluated experimentally.