Analysis of water balance in a PEFC at transient operation mode (effects of the properties of gas diffusion layers on the concentration overpotential in a PEFC with serpentine flow channels under start-up mode)

We have analyzed the dependence of the concentration overpotentials on the properties of gas diffusion layers (GDLs) of a polymer electrolyte fuel cell (PEFC) using dual serpentine flow fields during a start-up operation. Moreover, we directly and separately analyze such dependence of the amount of the water accumulated at each component of a cell by measuring the weight of adherent water. As a result, the hydrophobic treatment with micro porous layer addition to a GDL substrate is found to be effective to improve the cell performance by suppressing the water accumulation at the electrode (catalyst layer) which increases the concentration overpotential. Suppressed water accumulation at the electrode also increases cumulative current that represents the power generation and calorific power important for warm-up. Besides, increase in the coarseness of the GDL substrate is not so effective for decreasing the concentration overpotential and increasing the cumulative current for the case of the serpentine flow field. Increase in the thickness of the GDL substrate increases the concentration overpotential and decreases the cumulative current. These results will offer proper design parameters of GDLs for improving the performance of PEFCs, in particular during start-up.