Study of the mechanical interaction between gas diffusion layers and bipolar plates in low temperature fuel cells

Kurzfassung

In PEFC and DMFC the reaction and product gases and liquids will be transported in the channels of the bipolar plates as well as the gas diffusion layers. When optimizing fuel cells each of the components is commonly optimized independently. The interaction of the different fuel cell components is frequently neglected. Because both, bipolar plates and gas diffusion layers have to distribute and collect gases and liquids it is clear that the interaction of both components cannot neglected. CEA and DLR, in cooperation, have started to investigate these interactions; at first, the mechanical effects were investigated, whereby this work was mainly focused on the electrical contact resistance, the compression of the gas diffusion layers and the impression of the gas diffusion layer into the flow field channels. For this propose, at CEA the contact resistance and the change of thickness were measured during cyclic change of the pressure. In this way the dependence of both, contact resistance and thickness, on pressure and cycle number were determined. At DLR the impression of the gas diffusion layers into the flow field channels as a function of pressure was determined by three different methods: optically, change of the pressure drop over the flow field and electronically. The results and consequences will be presented.