操作參數對鍍金發泡鎳質子交換膜燃料電池性能影響研究

Effect of Operational Parameters on the Performance of a Proton Exchange Membrane Fuel Cell Assembled with Au-coated Ni-foams

本論文主旨在於利用鍍金發泡鎳代替傳統炭板流道來組裝製作質子交換膜燃料電池，並藉由直流電化學法與電化學交流阻抗法探討不同操作參數（如電池操作溫度、陰極進氣加濕溫度、陰極進氣計量比等），對於鍍金發泡鎳燃料電池性能之影響。結果顯示：電池的操作溫度由40提高到60℃時，電池之功率由326.6 mW/cm2增高到706.7 mW/cm2，其內部的質傳電阻由0.030Ω降至0.010Ω，若操作溫度低於40℃，則不利於電池內部氧還原反應（ORR）之進行。提高陰極進氣加濕溫度，將會導致電池之功率由733.6 mW/cm2降至622.3mW/cm2，量出電池內部對應的電荷轉移電阻由0.040Ω增加至0.100Ω,或可能因部分淹水所致。另外，陰極進氣計量比由2增加到5時，電池內部因空氣濃度增高，而有利於氧氣還原反應的加速進行。綜合所有操作條件之實驗結果顯示：本鍍金發泡鎳燃料電池系統在電池操作溫度為60℃、陰極進氣加濕溫度為50℃與陰極進氣計量比5時，具有最大輸出功率密度791.6 mW/cm2。

In this study, a new proton exchange membrane fuel cell (PEMFC) was assembled with a gold-coated nickel foam instead of conventional flow-field (carbon plate), and its performance which was related to operational parameters was evaluated by DC polarization and electrochemical impedance spectroscopy (EIS) technologies. Parameters such as operation temperature, temperature of cathode humidification and chemical stoichiometry in the cathode were of concern. The results revealed that the cell power density increased from 326.6 mW/cm2 to 706.7 mW/cm2, and the mass-transfer resistance decreased from 0.030 Ω to 0.010 Ω, with an increase in the operation temperature of the cell from 40 oC to 60 oC. It was found that an operation temperature of lower than 40 oC would deter the mass transfer rate of the oxygen reduction reaction (ORR). When the humidification temperature at the cathode increased from 50 oC to 70 oC, the cell power density decreased from 733.6 mW/cm2 to 622.3 mW/cm2. This decrease was ascribed to an increase in charge-transfer resistance of the cell from 0.040 Ω to 0.100 Ω, possibly caused by partial flooding. In addition, the performance of the cell was greatly improved when the chemical stoichiometry at the cathode was increased from 2 to 5. In summary, a maximum cell power density (i.e., 791.6 mW/cm2) could be achieved with a cell operation temperature of 60 ℃, a humidification temperature 50 oC at the cathode, and a chemical stoichiometry of 5 at the cathode for this PEMFC assembled with Au-coated nickel foams.