2019 Volume 76 Issue 3 Pages 196-206
The catalyst layers in fuel cells are manufactured by drying slurries called catalyst inks. Since cracks which often appear in the catalyst layer affect the performance of fuel cell, it is important to control the formation of the cracks in the manufacturing processes. Understanding the formation mechanisms of cracks helps to control the crack formation. However, the mechanisms are not sufficiently clarified because catalyst inks are complex slurries. In this paper, we investigated the density structures during the drying processes of catalyst layers in a fuel cell by radiography observations using synchrotron X-rays at the SPring-8 BL33XU beam line in order to clarify the crack formations. The results reveal that the cracks are generated at lower density areas than the surroundings as well as at clumps in the drying film. We conclude that controlling both the density distribution during the drying process and the clumps in the catalyst ink is effective for controlling the size and concentration of the cracks.
