Abstract: GDL(gas diffusion layer) is one of the critical components of a fuel cell and its basic functions are to provide channels for diffusion of gas from fluid to catalyst layer and for drain of liquid water from catalyst layer to fluid.In order to meet service conditions, the understanding for structure-performance of GDL is very essential, such as key parameters structure, porosity, hydrophobicity, hydrophilicity, gas permeability, transport properties, water management and their roles.A mathematics model of 1D and two-phase was built for GDL in cathode of proton exchange membrane fuel cell(PEMFC).A direct numerical procedure was applied for combined equations of the model and Leverett's and Fick's laws to analyze the profiles of liquid water saturation and oxygen concentration across the gas diffusion layer.The effect of GDL characteristics, such as porosity, thickness, contact angle and absolute permeability was discussed.The results show that its hydrophobicity is helpful for removal of liquid water.The effect of contact tangle on liquid water saturation and oxygen mass transfer becomes less and GDL porosity and thickness has little effect on liquid water saturation at the hydrophobic condition, but porosity and thickness of GDL play an important role in oxygen transfer.For practical use, both GDL porosity and thickness increase, there is no significant difference for limiting current density. Tafel slope and limiting current density predicted by the model agree well with the experimental observation from literatures.

Key words: cathode GDL, water flooding, liquid water saturation, limiting current density, PEMFC

摘要： 建立质子交换膜燃料电池一维两相传递模型,通过达西定律和菲克定律的联立求解得到扩散层中的液体饱和度和氧气浓度分布。考察扩散层特性参数孔隙率、厚度、接触角、渗透率对阴极水淹的影响,结果表明扩散层表面憎水将有助于液态水移出,但当达到憎水条件后,增大接触角对液态水传输和氧气传质的影响逐渐变小。憎水条件下孔隙率和厚度对液态水传输的影响不是很明显,但孔隙率增大和扩散层厚度减小均有利于氧气传质,实际应用中孔隙率增大的同时,厚度也要适当增大,极限电流密度相差不大。模型计算结果与文献中不同PTFE含量条件下实验的Tafel斜率和极限电流密度比较,吻合较好。

关键词: 阴极扩散层, 水淹, 液体饱和度, 极限电流密度, PEMFC