Analysis of Electric Generation Distribution on PEFC Electrode (1st Report, Electric Generation Distribution under Rib and Gas Channel on 1 mm Rib Width Cell)

We have evaluated resistances under the channel and rib of the separator in a polymer electrolyte fuel cell (PEFC) from the change of overpotentials by removing the gas diffusion layer (GDL) under the channel. As a result, we find that contact resistance between the GDL and electrode under the channel amounts to twelve times larger than that under the rib, leading to electron transfer rate limited reaction under the channel. Accordingly, the current ratio under the rib is calculated to be more than 90%. The ratio increases as the total current density increases when the current density is small, and it becomes almost constant as the current densiy becomes larger. The large current ratio under the rib suggests that the vapor produced in the electrode under the rib transfers toward that under the channel and accumulate there. Thus the major part of the vapor is probably carried away through the MPL and GDL base material under the channel by the cathode gas flow in the channel.