應用團塊理論分析一氧化碳毒化效應對PEMFC暫態性能之影響

Abstract

本研究主要，針對質子交換膜燃料電池中陽極觸媒層內之一氧化碳毒化現象進行理論分析。使用之理論模式為包含團塊模式與毒化模式之暫態傳輸行為，並給定邊界條件，求得一氧化碳毒化在觸媒層內氫氣、一氧化碳、覆蓋率、電流密度的分佈情形與達穩態所需的時間。研究中主要是改變不同的一氧化碳濃度、觸媒層厚度以及觸媒顆粒半徑的改變，來探討不同條件對電池內部所產生之影響。 研究結果顯示，隨著一氧化碳濃度愈低，氫氣含量越高時，電池系統啟動後，需較長的時間達到穩態。在相同20μm 觸媒層厚度下，Agglomerate模式，探討氫氣、一氧化碳濃度和覆蓋率的分佈情況時，仍可看出在20μm厚的觸媒層處，有明顯擴散現象，但Homogeneous模式下，探討氫氣、一氧化碳濃度和覆蓋率的分佈情況時，只能看出在10μm厚的觸媒層處，有明顯擴散現象。然而，在改變觸媒顆粒半徑及觸媒層厚度情況下，觸媒半徑在10nm和觸媒層厚度在10μm時，電流密度均達到一個最佳值。

The behavior of poisoning phenomena in the anode catalyst layer for polymer electrolyte fuel cells were considered in this study. According to boundary conditions, computational solutions of hydrogen, carbon monoxide concentration, preferentially adsorbing to the platinum surface and current density in catalyst layer and the time to reach stability were obtained by using agglomerate model and langmuir model. Our discussion focuses on the effects of different carbon monoxide concentration, catalyst layer thickness, and catalyst pellet radius on the performance of polymer electrolyte fuel cells. The results show that a long steady state can be achieve using pure hydrogen at a relatively low CO content. At the same thickness of the anode catalyst layer for both model, this phenomena of hydrogen, carbon monoxide concentration and coverage rate are concentrated within the outermost 20μm of the active layer in the agglomerate model, diffusing and absorbing into the inner part of the active layer, but the homogeneous model are concentrated within the outermost 10μm of the active layer. However, in the situation of different catalyst layer thickness and catalyst pellet size, the thickness of 10μm and the pellet radius of 10nm has the maximum current density.