醇/水混合溶劑應用於全氟磺酸質子交換膜電極組製備

Preparation of Nafion-based membrane electrode assemblies using alcohol/water mixture solvents

吳昌村(Ngo Trung Truc)

指導教授 ： 余 子 隆

元智大學/工程學院/化學工程與材料科學學系/博士(2013年)

https://doi.org/10.6838/YZU.2013.00019

摘要

本論文研究全氟磺酸(Nafion)高分子在稀釋異丙醇/水溶液及稀釋甲醇/水溶液中的分子形態.我們也研究鉑-碳與全氟磺酸高分子及甲醇/水混合溶液塗布於碳紙之觸媒電極上的全氟磺酸高分子的分子形態.
我們發現燃料電池的性能與全氟磺酸高分子在觸媒溶液中的分子形態有緊密關係. 觸媒溶液中的醇含量較低會造成全氟磺酸高分子在溶液中聚集,形成帶負電荷的大聚集粒子. 帶負電荷的大聚集粒子產生的立體障礙,使得噴塗觸媒溶液於碳紙製作的觸媒電極之全氟磺酸高分子層與觸媒-碳粒子之間有較大空隙. 觸媒-碳粒子表面接觸的全氟磺酸高分子層較薄. 較薄的全氟磺酸高分子層使得鉑觸媒與氫/氧氣體分子有較大的接觸機率,增加電化學反應效率,提升燃料電池性能.
我們探討全氟磺酸高分子在鉑觸媒層中的分子形態與燃料電池性能的相關性. 發現鉑-碳與全氟磺酸高分子及醇/水混合溶液中的醇/水溶劑的介電常數與溶解參數 是決定全氟磺酸高分子在鉑觸媒層中的分子形態與燃料電池性能的重要因子. 而以鉑-碳與全氟磺酸高分子及甲醇/水混合溶液中的醇/水溶劑的介電常數與溶解參數描述觸媒電極及燃料電池性能可能比以醇/水溶劑的組成描述觸媒電極及燃料電池性能更精確.

關鍵字

全氟磺酸高分子形態 ； 全氟磺酸高分子稀釋溶液 ； 鉑觸媒電極 ； 膜電極組 ； 質子交換膜燃料電池

並列摘要

We study the morphology of Nafion in the dilute IPA (isopropyl alcohol)/water and the dilute methanol (MeOH)/ water mixture solutions containing 20-100 wt.% of IPA and MeOH, respectively. We also study the morphology of Nafion in the Pt-C/Nafion gas diffusion electrodes (GDEs; where Pt-C is the carbon powder deposited on its surface with Pt particles) prepared by spraying on the carbon paper surfaces with a layer of Pt-C, Nafion, and alcohol/water ink solution.
The fuel cell (FC) performance of the GDEs strongly depends on the Nafion morphology in the ink solutions. A lower alcohol content in the Pt-C/Nafion ink solutions results in the formation of larger and higher negatively charged Nafion aggregated particles, which leads to higher steric hindrance of the deposition of Nafion ionomer on the surface of Pt-C particles and thus a thinner Nafion film in contact on the Pt-C particle surfaces. The thinner Nafion film in contact with the Pt particles in the CL increases the chances of the Pt particles in contact with the H2/O2 gas, leading to a higher FC performance.
The morphology of Nafon ionomer in the CLs and the FC performances of the GDEs are discussed based on the dielectric constants s and the solubility parameters s of the alcohol/water mixture dispersion solvents of the catalyst ink solutions, which are used for fabricating GDEs and preparing membrane electrode assemblies (MEAs). By plotting the Pt electrochemical surface area (Pt-ECSA) of GDEs and the FC performance of MEAs against the  and  of the alcohol/water mixture dispersion solvents of the catalyst ink solutions, we demonstrate that the GDEs and MEAs have similar Pt-ECSA and FC performance, respectively, when the alcohol/water mixture dispersion solvents of the catalyst ink solutions have similar  and  values, whether MeOH or IPA is in the mixture solvents. The  and  are better parameters than the compositions of the alcohol/water mixture solvents to describe the GDE and fuel cell performances.

並列關鍵字

Nafion morphology ； Nafion dilute solutions ； Platinum catalyst electrodes ； Membrane electrode assembly ； Proton exchange membrane fuel cell

參考文獻

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