Chemical Stability Investigations of Catalyst Layer in PEMFC

本文采用 Fenton 试剂离线加速衰减测试考察质子交换膜燃料电池（PEMFC）催化层的化学稳定性. 在经100 h Fenton 试剂处理后，氟离子流失测试和傅里叶红外光谱表征（ATR-FTIR）证明催化层中全氟磺酸离聚物（Nafion）发生了化学降解；通过透射电镜（TEM）观察到催化层中发生了明显的 Pt 颗粒团聚和炭载体腐蚀，与TEM表征相一致，循环伏安测试（CV）表明电化学活性面积（ECSA）降低了58%，并伴随着双电层区域的明显减少；FTIR测试进一步表征了炭载体的表面状态，并没有观察到明显的含氧官能团的产生，减少的炭载体可能以CO2的形式释放出去. 全电池测试表明，自由基攻击对催化层组成和结构造成了明显损坏，显著增加了催化层中的质子传导阻力和局部气体传输阻力，导致全电池性能大幅降低.This work was intended to study the effect of free radicals on the chemical stability of catalyst layer via ex situ accelerated stress test (AST). Fenton reagent was used as the free radical provider in this research. Apart from the decomposition of Nafion in catalyst layer, the agglomerated Pt nanoparticles and the corroded carbon support were also observed after being treated in Fenton reagent for 100 h. Firstly, the existence of fluoride (F) ions evidenced the chemical decomposation of Nafion after being attacked by trace radical species, which was supported by the intensity decrease in the C-F stretching and vibration peak (1250 cm-1) observed in attenuated total reflection Fourier transform infrared (ATR-FTIR) spectrum. The transmission electron microscopic (TEM) studies showed that the severe Pt nanoparticles agglomeration and carbon support corrosion happened. To gain more insight, the cyclic voltammetry (CV), ATR-FTIR and single cell performance measurements were conducted. A large loss (58%) of the electrochemical active surface area (ECSA) was observed. Another meaningful finding was the reduced double layer region, which demonstrated the reduction of carbon support. Notably, further ATR-FTIR analysis revealed the disappearance in the spectra at 1719 cm-1 ~ 1578 cm-1 which were assigned to the hydroquinone-quinine (HQ-Q) redox couple on the oxidized carbon surface. On the bases of these results, it could be concluded that carbon support might be decayed by releasing CO2 instead of forming oxides on its surface. Finally, the single cell performance data indicated an obvious performance loss in high current density range, due to the proton and local gas transport limitations in the decayed electrodes.国家科技支撑计划项目（No. 2015BAG06B00）和国家重点研发计划（No.2016YFB0101302）资助作者联系地址：1.中科院大连化学物理研究所，辽宁大连 116023; 2.中国科学院大学，北京 100039； 3.大连擎研科技有限公司，辽宁 大连 116023Author's Address: 1.Dalian Institute of Chemical Physics，Chinese Academy of Sciences, Dalian 116023, Liaoning, China; 2. University of Chinese Academy of Sciences, Beijing 100039, China; 3. Dalian Innoreagen Co., Ltd, Dalian 116023, Liaoning, China通讯作者E-mail：[email protected]

Preparations and Properties of Polybenzimidazole/PolyVinylbenzyl Crosslinked Composite Membranes for High Temperature Proton Exchange Membrane Fuel Cells

为提高聚苯并咪唑（PBI）膜的抗氧化性能，以乙烯苄基氯（PVBC）作为PBI的大分子交联剂，并利用1H-1,2,4-三氮唑取代交联剂中的不稳定端基Cl，制备了交联型高温质子交换膜，考察了交联剂用量对膜的电化学性质的影响. 研究表明，膜中的交联结构有效提高了膜的抗氧化性能，并兼具优异的电导率及力学性能. 采用无增湿H2和O2对膜电极性能进行了测试，150 oC下电池最大功率密度达到0.82 W•cm-2.In order to increase the chemical stability of polybenzimidazole (PBI) membrane, a highly stable polymer, poly vinylbenzyl chloride (PVBC), was chosen as the macromolecular crosslinker, and 1H-1,2,4-triazol was adopted to prepare the crosslinked PBI-based membranes. The influence of the PVBC amount on membrane characteristic was investigated in detail. The results indicated that the crosslinked structure of the membrane effectively improved the chemical stability, and at the same time, the membrane presented good mechanical property and proton conductivity. The fuel cell performance for the membrane was tested with hydrogen and oxygen single cell without humidification at 150 oC, and the maximum power density reached 0.82 W?cm-2.国家自然科学基金项目（No. 21436003，No. 61433013）、国家高技术研究发展计划（No. 2013AA110201）作者联系地址：1. 中科院大连化学物理研究所，辽宁 大连 116023；2. 中国科学院大学，北京 100039Author's Address: 1. Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China; 2. University of Chinese Academy of Sciences, Beijing 100039, China通讯作者E-mail：[email protected]