| 摘要: | 質子交換膜燃料電池(PEMFC)是一種將反應物的化學能直接轉換成電能的電化學裝置，PEMFC可以透過減少觸媒層鉑金(Pt)使用量以降低電池生產成本並同時保持最大功率密度來進行大規模生產和商業化，當Pt膜厚度超過最佳值時，氣體傳輸良好的區域(靠近氣體擴散層的一側)與質子傳輸良好的區域(靠近質子交換膜的一側)分離，因此電流密度和功率密度隨膜厚度的新增而下降。本研究是藉由COMSOL軟體來模擬質子交換膜燃料電池，使用多重物理量耦合的方式，建立三維燃料電池模型，並以此模型為基準，來分別模擬兩相的單電池。而在模擬的區域則包含了陰極和陽極兩端的流道、氣體擴散層、微孔層、觸媒層以及質子交換膜。
本研究藉由COMSOL Multiphysic在微孔層表面上製造不同週期性凹槽，以增加Pt沉積的有效表面積，從而減少Pt膜厚度，透過改變凹槽的形狀、寬度以及深度，討論對於質子交換膜燃料電池性能影響。研究結果顯示，在40 µm凹槽深度具有較高的電流密度，凹槽越深其PEM燃料電池性能越好。而在不同凹槽形狀中使用方形週期性凹槽且深度及寬度皆為40 µm的情況，0.6 V下的電流密度較無凹槽提升約26 %。
本研究同時對於金屬多孔材流場設計的質子交換膜燃料電池進行參數靈敏度分析。該模型耦合了多組分反應物和液態水的兩相流、物種傳輸、電化學反應、質子和電子傳輸。此項研究參數可以分為各層(氣體擴散層、微孔層、觸媒層以及質子交換膜)結構或傳輸參數(曲折度、孔隙率、滲透率及導電率)，以及電化學參數(陽極和陰極交換電流密度、陽極和陰極轉移係數)，並且進行單個參數不同數值模擬，得出不同參數對電池極化曲線的影響，分析影響燃料電池性能的因素。
;Proton exchange membrane fuel cell (PEMFC) is an electrochemical device that directly converts the chemical energy of reactants into electrical energy. Platinum (Pt) used as a catalyst layer in the PEMFC increases the cost of the fuel cell. This study aims to increase the higher surface area of the catalyst layer with lower catalyst loading. So that the cost of the PEMFC could decrease. When the thickness of Pt membrane exceeds the optimal value, the region with good gas transmission (near the gas diffusion layer) is separated from the region with good proton transmission (near the proton exchange membrane), so the current density and power density decrease with the increase of membrane thickness. In this study, the proton exchange membrane fuel cell is simulated by COMSOL software, and a three-dimensional fuel cell model is established by coupling multiple physical quantities happen in the actual (physical) functioning of PEMFC. The model couples the two-phase flow of multicomponent reactants and liquid water, species transport, electrochemical reaction, proton and electron transport. Based on this model, single cell is simulated with liquid and gaseous media flow in the porous solid system respectively. The simulated region includes the flow channels at both ends of cathode and anode, gas diffusion layer, microporous layer, catalyst layer and proton exchange membrane. In this study, COMSOL multiphysics was used to make different periodic grooves on the surface of cathode and anode microporous layer to increase the effective surface area of Pt deposition, so as to reduce the thickness of Pt membrane. The effects of groove shape, and depth on the performance of PEMFC is investigated. Groove depth increases the performance of PEMFC. The research results show that the groove depth of 40 µm has the highest current density, the better performance of PEM fuel cell. The PEMFC current density is 26% higher at 0.6 V for a square periodic groove of 40 µm. At the same time, the parametric sensitivity analysis of PEMFC with porous flow field design is carried out. The model couples the two-phase flow of multicomponent reactants and liquid water, species transport, electrochemical reaction, proton and electron transport. The research parameters can be divided into the structure or transmission parameters (tortuosity, porosity, permeability and conductivity) of each layer (gas diffusion layer, microporous layer, catalyst layer and proton exchange membrane) and electrochemical parameters (anode and cathode exchange current density, anode and cathode transfer coefficient). Different numerical simulations of single parameters are carried out to obtain the influence of all parameters on the polarization curve of the cell and analyze the factors affecting the performance of the fuel cell. This study helps in decreasing the cost of PEMFC and increasing the performance of PEMFC with optimum Pt thickness and microporous layer groove design. |
