傳統質子交換膜燃料電池膜電極組結構，由一個質子交換膜為中心，以三明治形式依序往外，兩面各夾一層Pt/C-40觸媒層（白金金屬含量40 wt％），其觸媒層外再各夾一層氣體擴散層，組合成五層的膜電極組（結構a）。本研究藉由修改傳統膜電極組結構包含：（1）將Pt/C-80觸媒漿料（白金金屬含量80 wt％）塗佈於Pt/C-40觸媒層與質子交換膜之間，形成七層的膜電極組（結構b）；（2）將Pt/C-80觸媒漿料塗佈於Pt/C-40觸媒層與氣體擴散層之間，形成七層的膜電極組（結構c）；（3）將Pt/C-80與Pt/C-40觸媒漿料混合，塗佈於質子交換膜與氣體擴散層之間，形成五層的膜電極組（結構d）。在固定的白金金屬載量中，經研究發現調整型膜電極組結構b、結構c和結構d，均比傳統型膜電極組結構a有更好的電池性能。其性能提升之主要原因，推論為觸媒層厚度降低，減少陽極端H+離子傳遞至陰極端的距離（增加導離子度），使得與陰極端的反應縮短，並降低質子傳遞阻抗。 本文亦藉由二維數值模擬分析之觀點，探討影響性能之原因。根據模擬結果顯示，調整型膜電極組電池性能比傳統型較佳的結果與實驗相符。主要原因則包含：質子傳導度、開路電壓，及觸媒層厚度等。同時亦觀察到不同膜電極組之水分佈情形；當Pt/C-80觸媒層介於氣體擴散層與Pt/C-40觸媒層之間（即結構c膜電極組），可發現膜電極組內有較多的液態水堆積。;The conventional 5-layer membrane electrode assembly (MEA) consists of a proton exchange membrane (PEM) locating at its center, two layers of Pt/C-40 (Pt content 40 wt%) locating next on both surfaces of PEM, and two gas diffusion layers (GDL) locating next on the outer surfaces of Pt/C layers (structure-a MEA). In this paper, we report three modified MEAs consisting of Pt/C-40 (Pt content 40 wt%) and Pt/C-80 (Pt content 80 wt%) catalysts. These are: (1) 7-layer structure-b MEA with a thin Pt/C-80 layer locating between Pt/C-40 layer and PEM; (2) 7-layer structure-c MEA with a thin Pt/C-80 layer locating between Pt/C-40 layer and GDL; and (3) 5-layer structure-d MEA with Pt/C-40 and Pt/C-80 mixing homogeneously and locating between PEM and GDL. Under a fixed Pt loading, we find structure-b, -c, and -d MEAs with 20 ~ 40 wt% Pt contributed from Pt/C-80 have better fuel cell performance than structure-a MEA consisting only of Pt/C-40. The reasons are attributed to the better feasibility for H2/O2 gas to reach Pt particles and lower proton transport resistance in catalyst layers of the modified MEAs than structure-a MEA. On the other hand, a two-dimensional, multi-phase, non-isothermal numerical model was used to investigate the effect of the high performance catalyst layer design. Simulation results show that substituting part of the Pt/C 40 wt% with Pt/C 80 wt% increases the cell performance. It was found that factors including proton conductivity, open circuit voltage and sub-layer thickness have a significant impact on overall cell performance. Different water distribution for different MEA designs was also observed in the simulation results. More liquid water accumulation inside the MEA is seen when the Pt/C 80 wt% sub-layer is next to the gas diffusion layer (structure-c MEA).
