Insight into the Rapid Degradation Behavior of Nonprecious Metal Fe-N-C Electrocatalyst-Based Proton Exchange Membrane Fuel Cells
Insight into the Rapid Degradation Behavior of Nonprecious Metal Fe-N-C Electrocatalyst-Based Proton Exchange Membrane Fuel Cells
复制标题
深入了解基于非贵金属 Fe-N-C 电催化剂的质子交换膜燃料电池的快速降解行为
DOI：
10.1021/acsami.9b13474
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发表时间：
2019-10-16
影响因子：
9.5
通讯作者：
Zhang, Junliang
中科院分区：
文献类型：
--
作者：
Chen, Junren;Yan, Xiaohui;Zhang, Junliang
近年来，非贵金属催化剂作为质子交换膜燃料电池中替代铂的替代材料，取得了很大的进展。非贵金属催化剂Fe-N-C在转盘电极实验中表现出与铂相似的催化活性，但Fe-N-C催化剂基燃料电池的快速降解现象限制了其实际应用。虽然已有大量的研究致力于研究催化剂本身的降解，但对膜电极组件的关注较少，这使得燃料电池的降解机理尚不清楚。本工作制备了一种高性能的Fe-N-C催化剂基膜电解液组件，并对其降解机理进行了研究。该燃料电池的初始峰值功率密度高达1.1W cm(-2)，但在0.4V下仅20h的电流损耗为52%。实验和密度泛函计算结果表明，催化剂活性中心的铁受到过氧化氢分解产生的羟基自由基的攻击，并被进一步浸出，导致活性损失增加。铁离子进一步污染了催化层和膜的离聚体，导致膜电阻和阴极催化层质子传导电阻增大，大大影响了电池的性能。另外，以前的研究认为Fe-N-C基燃料电池的快速性能损失是由于催化层内的水淹造成的，这一假设在我们的研究中被干涸实验证明是不正确的。
In the past few years, great progress has been made in nonprecious metal catalysts, which hold the potential as alternative materials to replace platinum in proton exchange membrane fuel cells. One type of nonprecious metal catalyst, Fe-N-C, has displayed similar catalytic activity as platinum in rotating disk electrode tests; however, rapid degradation of Fe-N-C catalyst-based fuel cells is always observed, which limits its practical application. Although considerable research has been devoted to study the degradation of the catalyst itself, rather less attention has been paid to the membrane electrode assembly that makes the mechanism of fuel cell degradation remain unclear. In this work, a high-performance Fe-N-C catalyst-based membrane electrolyte assembly is prepared and used to study its degradation mechanism. The fuel cell performs with an initial peak power density as high as 1.1 W cm(-2) but suffers a current loss of 52% at 0.4 V over 20 h only. The experimental and DFT calculation results indicate that Fe at active sites of catalysts is attacked by hydroxyl free radicals decomposed from H2O2, which is further leached out, causing an increase in activity loss. The ionomer of the catalyst layer and the membrane is further contaminated by the leached Fe ions, which results in an enlarged membrane resistance and cathode catalyst layer proton conduction resistance, greatly influencing the cell performance. In addition, it has been assumed in previous studies that the quick performance loss of Fe-N-C-based fuel cells is caused by water flooding within the catalyst layer, which is proved to be incorrect in our study through a dry-out experiment.