研究生: |
林君孟 Jun-meng Lin |
---|---|
論文名稱: |
陽極材料設計應用於電解質支撐/陽極支撐固態氧化物燃料電池研究 Design and developing of anode material for Electrolyte/ Anode supported SOFC with controlled parameters |
指導教授: |
周振嘉
Chen-Chia Chou |
口試委員: |
郭東昊
Dong-Hau Kuo 鄭逸琳 Yih-Lin Cheng |
學位類別: |
碩士 Master |
系所名稱: |
工程學院 - 材料科學與工程系 Department of Materials Science and Engineering |
論文出版年: | 2008 |
畢業學年度: | 96 |
語文別: | 中文 |
論文頁數: | 118 |
中文關鍵詞: | 固態氧化物燃料電池 、陽極支撐 、陽極設計 |
外文關鍵詞: | SOFC, anode supported SOFC, anode design |
相關次數: | 點閱:238 下載:1 |
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為了降低燃料電池工作溫度的需求,本論文使用新型高離子導材料與陽極支撐系統來改善固態氧化物燃料電池(SOFC)半電池的電化學反應。40wt.%高離子導系統材料Zr0.92Y0.155Mg0.005O2.0775 (YMSZ)混合60wt%氧化鎳改良陽極膜應之材料系統用以改進電解質支撐及陽極支撐之固態氧化物燃料電池。AC 阻抗圖譜技術用以檢視界面活性及陽極微觀所造成的信號,鐵弗曲線分析和功率密度測量分別用來觀察三相點之電化學反應與檢驗實際燃料電池轉換化學能為電能的效率。
SEM與EDS mapping結果顯示以乾壓成型製備陽極支撐層與網印法製備電解質、陽極活化層、陰極之陽極支撐SOFC共燒溫度於1350℃一小時,並於氣氛20%H2+80%N2溫度800℃持溫2小時下還原可達到陽極支撐電池電解質緻密與電極多孔之要求,並且各共燒溫度之白金陰極、電解質(8YSZ)、陽極活化層(Ni/YMSZ)、陽極支撐層(Ni/8YSZ)之間接合良好,無分層或剝落現象。陽極中,沒有鎳金屬明顯團聚之現象,陶瓷離子導體與金屬電子導體呈現均勻的網絡狀分布,顯示了良好的微觀形貌。
以Ni/YMSZ或Ni/8YSZ為陽極之電解質支撐半電池、Ni/8YSZ陽極支撐半電池、含Ni/YMSZ活化陽極於Ni/8YSZ陽極支撐之半電池,分析半電池於AC交流阻抗圖譜及活化能,顯示含Ni/YMSZ活化陽極之陽極支撐半電池因電解質較薄,且陽極有孔隙漸層之微結構設計使得離子導體及電子導體接合之處的三相點(TPB)增加,歐姆阻抗與電極極化阻抗皆較前兩者小,說明SOFC之電池性能的最佳化和電池材料、微結構設計及材料分佈有密切的關係。
本研究使用15%H2+85%N2 流量100sccm的燃料氣氛,Ni/8YSZ陽極支撐半電池於600℃電池最大功率密度為44mW/cm2,大於Ni/YMSZ陽極於電解質支撐半電池在600℃之功率密度(7.41 mW/cm2)、以及700℃時的功率密度(35.68mW/ cm2)。功率密度測試結果顯示,陽極支撐型電池在較低的工作溫度( <100℃) 有較佳的工作效率。因此陽極支撐型電池若添加陽極活化層將可用來提高SOFC於高、中溫的工作效率。這個製程在未來可應用於多個半電池疊合成的電池堆( cell stack ) 的裝置來產生高功率輸出。
In view of increasing demand to reduce the working temperature of the fuel cell, there is a need to search for high ionic conductivity electrolytes and to improve the design of the single cell as well as the anode material system for high electrochemical reaction. Hence in the present study, novel anode composite material made of 40wt.% Zr0.92Y0.155Mg0.005O2.0775 (YMSZ) and 60wt.% catalytic Ni particles was used to develop electrolyte support, anode support and buffer layer containing anode support solid oxide fuel cells. AC impedance spectroscopy technique was adopted to check interfacial property and anode structure, Tafel curve analysis was used to observe the performance of electrochemical reaction at the TPB’s and power density measurement was used to check the efficiency of the fuel cell in converting chemical energy into electrical energy.
Microstructure analysis using SEM and EDS mapping pictures shows that the co-sintering of anode supported the half cell at 1350℃for 1h had a dense electrolyte and anode/anode active layer with uniform distribution of ionic conducting YSZ/YMSZ particles and catalytic Ni particles, sufficient porosity and homogeneous network structure. The interfacial property between different components of the half cell was improved significantly by using co-sintering electrolyte, anode, anode active layer, cathode and current collectors.
AC impedance analysis of electrolyte-supported half cell (anode: Ni/YMSZ), Ni/8YSZ anode-supported half cell and anode-supported half cell with Ni/YMSZ active layer shows that the decreasing order of electro catalytic activity measured using area specific resistance is anode-supported cell with Ni/YMSZ active layer>Ni/8YSZ anode-supported cell>electrolyte-supported SOFC cell (anode is Ni/YMSZ). The least value of area specific resistance in anode supported cells is due to thinner electrolyte when compared to the electrolyte-supported cell. Furthermore, anode-supported cell with Ni/YMSZ active layer is found to decrease active polarization caused by the anode, because the active layer has more TPB sites near the interface and also due to homogenous distribution of composite particles observed from microstructure.
Exchange current density measured using Tafel curves indicates that the electrochemical reaction is faster in the anode supported half cell compared to that of half cell with electrolyte support.
The efficiency of the half cell in converting the chemical energy in to electrical energy was estimated by measuring the power density using 15%H2+85%N2 (100 sccm) as fuel and air as oxidant. Anode-supported cell has shown the power density of 44.05mW/cm2 at 600℃which is much higher than electrolyte-supported cell ( 7.41mW/cm2 at 600oC) and also better than the power density of electrolyte-supported cell measured at 700 ℃(35.68mW/cm2). The result on power density reveals that the efficiency of the cell with anode-supported structure shows better performance at lower temperatures (<100oC) than electrolyte supported half cell. Hence it can be concluded that the anode supported half cell containing Ni/YMSZ anode can be used to develop high efficiency half cells for high and intermediate temperature fuel cell applications. This process can also be applied to develop SOFC stack with multiple half cells for high power output in future.
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