抄録
In polymer electrolyte fuel cell (PEFC), water management is one of the most important issues. In the case that water concentration near the membrane is low, the protonic conductivity of membrane decrease. Whereas, if humidity reaches saturation level, fuel and oxidant gases supply is disturbed by liquid water. Optimization of the water concentration on the surface of the membrane is one of key points for further improvement of PEFCs. However many experiments are conducted with gas diffusion layer (GDL) which has random structure like carbon paper. Due to their complexity, it is difficult to reveal the inside phenomena. Also due to the random structure, it is impossible to do a detailed control of the GDL. In this study, we proposed a new method to control water by using surface energy gradient. Firstly, through theoretical study, we prove the principle of force caused by surface energy differences with triangle shape. And then, we demonstrate the effect in cell performance and the movement of water with Ti gas diffusion layer (Ti-GDL). We compare cell performances with two types of GDLs: one is GDL with circular type of hole, in which the water concentration cannot be managed, another is GDL with triangular type of hole, in which the water concentration can be managed by surface energy gradient. As a result, the cell with GDL with triangular type of hole showed a good performance compared with GDL with circular type of hole. Further we observed Ti-GDL with triangular type of hole keeps wettability with maintaining the gas supply path.
