Transport phenomena of proton and water in PEFC by MRI and its application to high stability and performance

聚合物电解质燃料电池（PEFCs）是一种很有前途的汽车和现场发电电源。聚合物电解质膜（PEM）是目前正在开发的用于PEFC堆的最重要的材料之一，它可以将质子从阳极传导到阴极，众所周知，它的质子导电性取决于它的含水量。这表明质子交换膜中的水与质子传导机制密切相关。在这里，我们证明了在电解液膜中，通过提供氢（H_2）或氘（D_2）作为燃料来取代^1H和^2D原子。通过提供氘作为燃料，D^+通过氧化反应进入电解质膜，并与作为磺酸基和/或水分子氢原子的反离子的质子取代。利用磁共振成像（MRI）技术测量了氢向重氢转换后氢原子分布的变化。磁共振图像清楚地显示，更多的H和D原子发生在阳极侧（燃料供应侧），D原子几乎取代了电解质膜中所有的H原子。这表明质子在聚合物电解质膜中的传导机制是“体机制”，即质子在膜亲水性区的水中通过Grotthuss机制进行传输，而不是“表面机制”或“载体机制”。水蒸气分布是聚合物电解质燃料电池（PEFC）由供气通道和多孔气体扩散层组成的阴极通道，为了阐明聚合物电解质燃料电池（PEFC）中GDL的多孔结构对供气水分分布和露点的影响，采用晶格玻尔兹曼方法（LBM）对其进行了计算。结果表明，GDL的孔隙率影响GDL中最大出水浓度，导致露点升高，孔隙率降低。另一方面，GDL中的孔隙尺度对PEFC阴极供气水浓度分布及其辅助露点的影响较小。少

Polymer electrolyte fuel cells (PEFCs) are promising power sources for vehicle applications and on-site power generation. One of the most important materials under development for PEFC stacks is a polymer electrolyte membrane (PEM), which conducts protons the anode to the cathode side, and it is well known that its proton conductivity depends on its water content. It implies that water in a PEM strongly relate to proton conducting mechanism. Here, we demonstrate the ^1H and ^2D atom replace in the electrolyte membrane by supplying hydrogen (H_2) or deuterium (D_2) as the fuel for the PEFC operation. By supplying deuterium as the fuel, D^+ comes into the electrolyte membrane by oxidation reaction, and replace with protons that are counter ion of sulfonic acid group and/or hydrogen atoms of water molecule. We measure the H atom distribution change after switching hydrogen to heavy hydrogen supply by the magnetic resonance imaging (MRI). The MR images clearly show that the replacement of … More the H and D atoms takes place in the anode side (fuel supply side), and D atoms replace almost all H atoms in the electrolyte membrane. This suggests the proton conducting mechanism in the polymer electrolyte membrane is 'bulk mechanism', which protons transport by Grotthuss mechanism in the water of hydrophilic region of the membrane^<7,8>, rather than 'surface mechanism' or 'vehicular mechanism'.Water vapor distribution is a cathode channel of polymer electrolyte fuel cell (PEFC) composed of gas supply channel and porous gas diffusion layer is calculated by lattice Boltzmann method (LBM) in order to clarify effect of porous structure of GDL in PEFC on water distribution and dew point of supplied gas. It is shown that porosity of GDL affects maximum water concentration emerged in the GDL, resulting in increase of dew point with decrease of porosity. On the other hand, pore scale in the GDL is less influential on water concentration distribution and its sesultant dew point of the supplied gas in the cathode of PEFC. Less