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Mechanism of improving oxygen transport resistance of polytetrafluoroethylene in catalyst layer for polymer electrolyte fuel cells
International Journal of Hydrogen Energy ( IF 7.2 ) Pub Date : 2018-03-20 , DOI: 10.1016/j.ijhydene.2018.01.091
Zhaohui Wan , Sufen Liu , Qing Zhong , Aiping Jin , Mu Pan

Oxygen transport resistance of catalyst layer (CL) has significant impact on the performance for polymer electrolyte fuel cells (PEFCs). Nano-Polytetrafluoroethylene (PTFE) particles are added into CL to improve the oxygen transport resistance. The CV curves indicate that PTFE do not reduce the utilization of Pt. The IV polarization curves suggest that the performance incorporated PTFE in CL gradually improve at high current densities and the output is 0.57 V at 1.8 A cm−2, 70 mV higher than that without PTFE. The water contact angle for CL with 20 wt% PTFE shows that continuous hydrophobic network may not be formed at 150 °C heat treatment temperature. The total transport resistance of CL with PTFE decreases about 2.5% at 70 °C and 250 kPa, mainly caused by the reduction of pressure-independent resistance (Rother). In the Rother reduction, the Knudsen diffusion resistance reduction in CL account for 74%. The pore size distributions reveal that the porosity increases 29% and the proportion of pores at around 100 nm increases for primary pores in CL with PTFE. This finding indicates that not the hydrophobicity of PTFE but the porous structure conducive to Knudsen diffusion for CL plays the predominant role in improving the performance.



中文翻译:

聚合物电解质燃料电池催化剂层中聚四氟乙烯的耐氧输运性提高机理

催化剂层(CL)的耐氧气传输性对聚合物电解质燃料电池(PEFC)的性能具有重大影响。将纳米聚四氟乙烯(PTFE)颗粒添加到CL中以提高耐氧传输性。CV曲线表明PTFE不会降低Pt的利用率。I V极化曲线表明,在高电流密度下,CL中掺入的PTFE的性能逐渐提高,在1.8 A cm -2时输出为0.57 V,比不使用PTFE时高70 mV。CL与20 wt%PTFE的水接触角表明,在150°C的热处理温度下可能无法形成连续的疏水网络。CL的总输送阻力与PTFE下降约在70℃和250千帕2.5%,主要是由压力无关电阻(还原- [R其他)。在R其他减少时,CL的Knudsen扩散阻力减少占74%。孔径分布表明,对于含PTFE的CL的主要孔,孔隙率增加了29%,并且在约100 nm处的孔比例增加了。该发现表明,不是PTFE的疏水性而是有利于CL的Knudsen扩散的多孔结构在改善性能中起主要作用。

更新日期:2018-03-20
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