PEM燃料电池膜电极中的水传输行为∗

摘要

In order to avoid the “water flooding”,the excess water generating in PEM fuel cell should be drained timely.In this study,an experiment model was applied to analyze the path of water flow corre-sponding to the flow resistances based on the“flooding”between catalyst layer (CL)and gas diffusion lay-er (GDL).Narrow apertures in the largest pores of carbon paper gas diffusion layer are the primary resist-ance to liquid water penetration.After sufficient hydrostatic pressure is applied,water penetrates the lim-iting aperture and flows through the pore reaching the GDL surface.For the carbon paper GDL material, the pressure(~1 kPa)required for water to flow through the pores is much less than the pressure (~6 kPa)to penetrate the limiting aperture of the pores.Adding micro-porous layer (MPL)can obviously in-crease water penetrate resistance.The content of Teflon in the MPL has little effect on the water penetra-tion pressure.It is helpful to promote the water management in fuel cell by setting pilot holes on the car-bon paper GDL material.%为避免电池“水淹”,PEM燃料电池发生电化学反应产生的多余水必须及时排出。基于阴极催化层(CL)与气体扩散层(GDL)之间极易发生的“水淹”特点,建立实验模型,分析阴极催化层产生的水穿透碳纸气体扩散层材料到达气体流道的路径与阻力。在纵向传输过程中,GDL中最大孔中的最小孔径是限制水渗透的主要阻力。只有当水头压力足够大时,水才能进入并且穿过这些限制孔径的孔到达GDL材料表面。对于碳纸GDL材料,水在这些孔中流动时所需压力(~1 kPa)显著小于水初始穿透这些孔所需压力(~6 kPa)。增加微孔层(MPL)会明显增加液态水的穿透阻力,MPL 层中不同 Teflon 含量对水渗透压力影响不大。对碳纸GDL材料设置引导孔能显著降低液态水的渗透压力,有助于提升燃料电池中的水管理能力。