PEMFC阴极催化剂位置与氧气传质

Effects of catalyst position on oxygen transport in cathode of PEMFC

通过对PEMFC阴极活性层中反应气体(O2)的二维传质过程和电化学反应的数学模拟,研究了催化剂位置对O2传质的影响。结果表明:O2在电解质中的扩散阻力主要由O2较小的溶解度,特别是极低的扩散系数所致。催化剂位置与O2扩散阻力密切相关。少量部分被电解质覆盖的催化剂具有最好的O2传质能力,在扩散控制条件下,对整个阴极活性层性能的贡献可超过50%。大量完全被电解质覆盖的催化剂是改善活性层性能的关键。

A twodimensional mathematical model was presented considering both mass transport process and the electrochemical reaction within the cathode catalyst layer (CCL) in a proton exchange membrane fuel cell(PEMFC).The main objective was to evaluate the effects of catalyst position on oxygen transport within the CCL by solving the equations with finite element method.It was found that the great hindrance of polymer electrolyte to oxygen transport could be attributed to the small solubility and the extremely low diffusion coefficient of oxygen in the electrolyte.The model calculation revealed the obvious effects of catalyst position on oxygen transport.The catalysts,partially covered by the electrolyte,located at threephasepoint of gas,carbon and electrolyte,were observed to possess the best ability to oxygen transport.For the case of diffusion being a ratelimiting step,the contribution of the catalysts partially covered by the electrolyte to the performance of the CCL was predicted to be over 50%.The catalyst utilization efficiency could be optimized by the preferential location of platinum close to the threephasepoint. 