Analysis of Water Transport in Catalyst Layers - Effect of Different Carbon Supports

摘要

Water transport phenomena in catalyst layers (CLs) were investigated experimentally and analytically. Water transport resistance in CLs was regarded as being driven by the water activity gradient and examined using an equivalent circuit model consisting of two transport mechanisms in parallel. In this study, the effect of different carbon supports on water transport resistance was investigated. The experimental results showed that CLs with a carbon support of graphitized ketjen black displayed lower water transport resistance than CLs with a carbon support of ketjen black. One possible reason for that difference is that the tortuosity of the ionomer in the CLs differed depending on the carbon support shape. The water resistance values in the CLs calculated with the model were higher in both cases than the experimental results. This suggests the existence of another water transport path that is faster than the path in the ionomer.