Abstract In PEMFC, the oxygen transport resistance severely hinders the cell from achieving high performance. In this paper, pore-forming agent was used to optimize the pore size distribution of the catalyst layer (CL), and to study its effect on the mechanism of oxygen transport resistance, including molecular diffusion resistance, Knudsen diffusion resistance, and local O2 resistance in CL. The results showed that with the pore formation the cell performance had a significant improvement at high current density, mainly due to its better oxygen transport properties, especially under low platinum conditions. The addition of pore-forming agent moved the pore diameter toward a larger pore diameter with a range from 70 to 100 nm, and also obtaining a higher cumulative pore volume. It was found that the increase of the cumulative pore volume and larger pore size were conducive to the diffusion of oxygen molecules in CL, and the resistance caused by which was the dominant part in total transport resistance. Further tests indicated that the improvement of molecular diffusion resistance was much larger than that of Knudsen diffusion resistance in the catalyst layer after pore formed. In addition, the optimized pore structure will also get a higher number of effective pores, which resulted in an increased effective area of the ionomer on the Pt surface. The higher effective area of the ionomer was particularly beneficial for the reduction of local O2 resistance with low Pt loading.

中文翻译：

---

催化剂层孔径优化对PEMFCs氧传输阻力机制的影响

摘要 在 PEMFC 中，氧传输阻力严重阻碍了电池实现高性能。本文采用造孔剂优化催化剂层(CL)的孔径分布，研究其对氧传输阻力机制的影响，包括分子扩散阻力、Knudsen扩散阻力和局部O2阻力在 CL。结果表明，随着孔的形成，电池性能在高电流密度下有显着改善，这主要是由于其更好的氧传输性能，尤其是在低铂条件下。成孔剂的加入使孔径向更大的孔径移动，范围为70-100 nm，同时也获得了更高的累积孔容。发现累积孔体积的增加和孔径的增大有利于氧分子在CL中的扩散，其引起的阻力在总输运阻力中占主导地位。进一步的测试表明，孔形成后催化剂层中分子扩散阻力的提高远大于Knudsen扩散阻力。此外，优化后的孔隙结构也会获得更多的有效孔隙，从而增加了离聚物在 Pt 表面的有效面积。离聚物较高的有效面积特别有利于降低低 Pt 负载下的局部 O2 阻力。由其引起的阻力在总运输阻力中占主导地位。进一步的测试表明，在形成孔后的催化剂层中，分子扩散阻力的提高远大于Knudsen扩散阻力。此外，优化后的孔隙结构也会获得更多的有效孔隙，从而增加了离聚物在 Pt 表面的有效面积。离聚物较高的有效面积特别有利于降低低 Pt 负载下的局部 O2 阻力。由其引起的阻力在总运输阻力中占主导地位。进一步的测试表明，在形成孔后的催化剂层中，分子扩散阻力的提高远大于Knudsen扩散阻力。此外，优化后的孔隙结构也会获得更多的有效孔隙，从而增加了离聚物在 Pt 表面的有效面积。离聚物较高的有效面积特别有利于降低低 Pt 负载下的局部 O2 阻力。这导致离聚物在 Pt 表面的有效面积增加。离聚物较高的有效面积特别有利于降低低 Pt 负载下的局部 O2 阻力。这导致离聚物在 Pt 表面的有效面积增加。离聚物较高的有效面积特别有利于降低低 Pt 负载下的局部 O2 阻力。