PEFCにおけるMPLへの大細孔付与が凝縮水分布と酸素輸送抵抗要素に及ぼす影響

抄録

To increase the power output of polymer electrolyte fuel cells (PEFCs), careful water management is important, and a micro-porous layer (MPL) suppresses water accumulation near the catalyst layer (CL). This study applied the MPL added with larger size pores to promote the water removal, and investigated the effecs using the extended limiting current analysis developed by the authors. In this method, the increase in oxygen transport resistance due to water accumulation is separated into pressure-dependent and -independent components by introducing two indices determining the condensed water effects. The components approximately correspond to the transport resistances outside and inside of the CL respectively. The results showed that adding larger size pores reduces increases in the oxygen transport resistance under flooded conditions. The extended limiting current analysis revealed that the suppression in the resistance increases is mainly caused by smaller pressure-dependent component. Further, the observation of water distributions by a freezing method and cryo-SEM indicated that condensation of produced water in the large pores inhibits that in the normal pores.