S053032 Measurement of gas diffusion resistance of the porous materials for PEFC

In order to reduce the cost of fuel cell electric vehicles, it is essential to operate polymer electrolyte fuel cell systems under high current density and under low humidity conditions. To realize these operations, the reduction of oxygen transport resistance inside the fuel cell is very important issues. However, there are few studies to measure and to analyze the oxygen transport resistance of porous materials for PEFC. In this study, we developed the measurement method of oxygen diffusion resistance in porous materials which have various pore size and structural properties. In addition, the method can determine the molecular diffusion and the Knudsen diffusion. And using this method, we measured the gas diffusion resistance in carbon paper (CP), micro porous layer (MPL) and catalyst layer (CL). The diffusion resistances in CP and in CL were dominated by the molecular diffusion and by the Knudsen diffusion, respectively. On the other hand, that in MPL was influenced by both the molecular diffusion and the Knudsen diffusion. These phenomena are almost understood their Knudsen numbers.