Voltage degradation is the main parameter that determines the effective usable life of a fuel cell, here the influence of Pt/C% and relative humidity (RH%) on the voltage decay rate of a fuel cell is experimentally evaluated and reported. This study implements a stress test with frequent interrupts of purging for determining the durability of the fuel cells. In the course of the 1456 h stress test for each membrane electrode assembly (MEA), the polarization curve and electrochemical impedance spectroscopy (EIS) were measured. The experimental results make it evident that the lowest voltage degradation was 6 µV/h for MEA with 40% Pt/C tested under 70% RH while the highest was 183 µV/h recorded for MEA with 20% Pt/C tested under 90% RH. From EIS results, the ohmic resistance increased for all the tested MEAs, which is also reflected in the performance degradation. Field emission scanning electron microscopy images also indicate the delamination of MEA layers which in turn increases the electron transfer resistance. So, the decisive factors for the fuel cell performance degradation were flooding, catalyst surface contamination, and delamination of MEA layers due to repeated mechanical and chemical stresses.

中文翻译：

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Pt/C百分比和湿度对质子交换膜燃料电池电压衰减率的影响研究

电压衰减是决定燃料电池有效使用寿命的主要参数，这里通过实验评估和报告了 Pt/C% 和相对湿度 (RH%) 对燃料电池电压衰减率的影响。本研究实施了压力测试，经常中断吹扫以确定燃料电池的耐久性。在每个膜电极组件（MEA）的1456 h应力测试过程中，测量了极化曲线和电化学阻抗谱（EIS）。实验结果表明，在 70% RH 下测试的含 40% Pt/C 的 MEA 的最低电压降为 6 µV/h，而在 90% RH 下测试的含 20% Pt/C 的 MEA 的最高电压降为 183 µV/h相对湿度。从 EIS 结果来看，所有测试的 MEA 的欧姆电阻都增加了，这也反映在性能下降上。场发射扫描电子显微镜图像还表明 MEA 层的分层，这反过来又增加了电子转移阻力。因此，燃料电池性能下降的决定性因素是溢流、催化剂表面污染以及由于重复的机械和化学应力导致的 MEA 层分层。