Yamaguchi Makoto, Matsunaga Takuro, Amemiya Kazuki, Ohira Akihiro, Hasegawa Naoki, Shinohara Kazuhiko, Ando Masaki, Yoshida Toshihiko
Fuel Cell Cutting-edge Research Center (FC-Cubic), Technology Research Association , AIST Tokyo Waterfront Main Building, 2-3-26 Aomi, Koto-ku, Tokyo 135-0064, Japan.
Toyota Central R&D Laboratories , Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192, Japan.
J Phys Chem B. 2014 Dec 26;118(51):14922-8. doi: 10.1021/jp506814m. Epub 2014 Dec 10.
The dispersion of perfluorinated sulfonic acid ionomers in catalyst inks is an important factor controlling the performance of catalyst layers in membrane electrode assemblies of proton exchange membrane fuel cells (PEMFCs). The effect of water/alcohol composition on the dispersion of H-Nafion in water/1-propanol and water/ethanol solutions was studied by dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and (19)F nuclear magnetic resonance ((19)F NMR) spectroscopy. Hydrodynamic radii calculated from DLS decay profiles and the radii and interparticle distance of rod-like particles derived from SAXS profiles showed almost the same dependence on alcohol concentration. 1-Propanol was more effective than ethanol to induce changes in the characteristic lengths of the rod-like particles. The motional narrowing in the (19)F NMR spectra by addition of 1-propanol indicates selective solvation of the rod-like particles. We suppose this might have decreased their radii and induced their elongation, which eventually led to extension of the ordered regions as observed in the hydrodynamic radii. Our study helps to clarify the dispersion of Nafion in aqueous alcohol solutions, which has implications for the performance of PEMFCs.
全氟磺酸离聚物在催化剂油墨中的分散是控制质子交换膜燃料电池（PEMFC）膜电极组件中催化剂层性能的一个重要因素。通过动态光散射（DLS）、小角X射线散射（SAXS）和¹⁹F核磁共振（¹⁹F NMR）光谱研究了水/醇组成对H-Nafion在水/1-丙醇和水/乙醇溶液中分散的影响。由DLS衰减曲线计算得到的流体动力学半径以及由SAXS曲线得出 的棒状颗粒的半径和颗粒间距离对醇浓度表现出几乎相同的依赖性。1-丙醇比乙醇在诱导棒状颗粒特征长度变化方面更有效。加入1-丙醇后¹⁹F NMR光谱中的运动窄化表明棒状颗粒的选择性溶剂化。我们推测这可能减小了它们的半径并导致其伸长，最终导致如流体动力学半径中所观察到的有序区域的扩展。我们的研究有助于阐明Nafion在醇水溶液中的分散情况，这对PEMFC的性能有影响。
