Nechitailov Andrey A, Volovitch Polina, Glebova Nadezhda V, Krasnova Anna
Ioffe Institute, St. Petersburg 194021, Russia.
Institut de Recherche de Chimie Paris (IRCP), Chimie ParisTech, PSL Research University, CNRS, 75005 Paris, France.
Membranes (Basel). 2023 Mar 16;13(3):342. doi: 10.3390/membranes13030342.
The stability of new membrane-electrode assemblies of a proton-exchange membrane fuel cell with highly porous electrodes and low Pt loading, based on the proton-conducting polymer Nafion, was characterized in conditions of electrochemical aging. A comprehensive study of the effect of the microstructure on the evolution of the electrochemical characteristics of the new assemblies was obtained by voltammetry, electrochemical impedance spectroscopy, X-ray powder diffraction, and scanning electron microscopy. Because high (>70%) porosity provides intensive mass transfer inside an electrode, structural-modifying additives-long carbon nanotubes-were introduced into the new electrodes. PEM fuel cells with electrodes of a conventional composition without carbon nanotubes were used for comparison. The aging of the samples was carried out according to the standard accelerated method in accordance with the DOE (Department of Energy) protocols. The results show two fundamental differences between the degradation of highly porous electrodes and traditional ones: 1. in highly porous electrodes, the size of Pt nanoparticles increases to a lesser extent due to recrystallization; 2. a more intense "washout" of Nafion and an increase in ionic resistance occur in highly porous electrodes. Mechanisms of the evolution of the characteristics of structurally modified electrodes under electrochemical aging are proposed.
基于质子传导聚合物Nafion的具有高孔隙率电极和低铂负载量的质子交换膜燃料电池新型膜电极组件的稳定性，在电化学老化条件下进行了表征。通过伏安法、电化学阻抗谱、X射线粉末衍射和扫描电子显微镜，对微观结构对新型组件电化学特性演变的影响进行了全面研究。由于高孔隙率（>70%）可在电极内部提供密集的传质，因此在新型电极中引入了结构改性添加剂——长碳纳米管。使用具有不含碳纳米管的传统组成电极的质子交换膜燃料电池进行比较。样品的老化按照美国能源部（DOE）协议的标准加速方法进行。结果表明，高孔隙率电极与传统电极的降解存在两个根本差异：1. 在高孔隙率电极中，由于再结晶，铂纳米颗粒尺寸增加的程度较小；2. 在高孔隙率电极中，Nafion的“冲刷”更强烈，离子电阻增加。提出了电化学老化条件下结构改性电极特性演变的机制。
