| 摘要: | 本研究主要針對中高溫工作區間具有高質子導電率之SrCeO3和BaCeO3鈣鈦礦結構陶瓷材料進行研發，並嘗試應用於氫氣傳輸透膜與固態氧化物燃料電池。質子傳導型固態氧化物燃料電池因其具有良好的導電性，低活化能，且其工作溫度可降至500–800°C，對降低成本與延長電池壽命有明顯的效益。其主要燃料來源為氫氣，且氫氣可由甲醇、天然氣與化石燃料經分離純化加工而獲得。
首先，在氫氣傳輸透膜研究中，利用固態反應法可成功製備SrCe1-xZrxO3-δ (0.0 ≤ x ≤ 0.5)質子導體氧化物。藉由X光繞射儀，掃描式電子顯微鏡來鑑定材料晶體結構與觀察表面形貌；熱膨脹儀分析鋯含量摻雜對其收縮率和燒結性的影響。隨著鋯摻雜含量的增加會導致材料孔隙率隨之增加，且SrCe0.6Zr0.4O3-δ試片在1500oC燒結2小時可獲得最大孔隙率27.53%。同時將SrCe0.6Zr0.4O3-δ和SrZrO3利用束縛燒結成功製備出具多孔結構支撐層材料。此外，SrCe0.6Zr0.4O3-δ可不添加造孔劑與多階段燒結製程，即可製備成陶瓷支撐層材料，在氫氣傳輸透膜與氫氣純化應用上有其潛在優勢。
其次，在質子傳輸型固態氧化物燃料電池研究中，利用固態反應法可成功製備Ba0.8Sr0.2Ce0.6Zr0.2InxY0.2-xO3-δ氧化物質子導體氧化物，並探討銦摻雜對其在微觀結構、化學穩定性、導電性和燒結能力之影響。結果顯示，燒結溫度降至1450oC燒結4小時，可得到緻密結構之電解質Ba0.8Sr0.2Ce0.75In0.05Y0.2O3-δ，且導電率在800oC可達0.011 S cm-1。為了進一步提升質子傳輸型固體氧化物燃料電池之性能，分別從電解質與陽極材料進行製程上的改良。本研究選擇Ba0.8Sr0.2Ce0.75In0.05Y0.2O3-δ作為電解質材料並利用刮刀成型與共燒技術來製備陽極支撐電解質之單電池。調整氧化鎳與電解質之陽極材料成份比例，探討微結構、比表面積和導電率對其提升電池性能之影響。多孔結構的陽極材料提供燃料電池有足夠的機械強度與適當的路徑給予燃料氣體流入至電解質反應。另一方面，在刮刀成型技術上進行電解質厚度減薄製程的探討，其結果顯示單電池的表現隨著厚度減薄(60 μm至20 μm)可增加近兩倍之功率密度。在800、700與600oC下之單電池的功率密度分別達到314.2、259.5與150 mW cm-2。本研究在電解質減薄製程上對後續質子傳輸型固體氧化物燃料電池之製程應用上有很大的助益。
最後，探討並評估不同比例的合成氣燃料對質子傳輸型固體氧化物燃料電池之陽極支撐電解質單電池在性能表現之影響資料庫。結果發現，由於合成氣體中氫氣含量的減少與一氧化碳含量的增加，使得質子傳輸型單電池之功率密度逐漸下降。然而，合成氣體中產生的碳會沉積並阻擾陽極材料中鎳金屬的催化反應，進而影響電池性能的表現。因此，本研究結果顯示，電解質材料Ba0.8Sr0.2Ce0.75In0.05Y0.2O3-δ不僅具有高質子導電率，亦具有良好的化學穩定性，可應用於質子傳輸型固體氧化物燃料電池電解質材料之潛力。未來將嘗試製備平板型質子傳輸固體氧化物燃料單電池及其連接板零組件試製，預期可以建立高性能質子傳輸型固體氧化物燃料電池之陽極支撐電解質單電池的製程條件範圍。
;In this study, the SrCeO3-based and BaCeO3-based perovskite ceramic materials with high proton conductivity were developed which can applied on hydrogen transport membranes (HTM) and solid oxide fuel cells in its high- and intermediate- working temperature. The proton-conducting SOFC (P+-SOFCs) can operate at relatively low temperature (500–800°C) because of their higher conductivity, lower activation energy, and reduces the capital costs and prolongs cell lifetime. The hydrogen, is the source for SOFC, can be obtained by separation and purification of methanol, natural gas and fossil fuels.
Firstly, according the published result of hydrogen transport membranes research, SrCe1-xZrxO3−δ (0.0 ≤ x ≤ 0.5) proton-conducting oxides can be successfully prepared using a solid state reaction method. In this study, the effect of the Zr contents on the microstructures, shrinkages, and sintering of these SrCe1-xZrxO3−δ (0.0 ≤ x ≤ 0.5) were systemically studied by using X-ray Diffraction, Scanning Electron Microscopy, and Thermal dilatometer analysis (TDA). The SEMs shows that the porosities of sintered SrCe1-xZrxO3−δ increased with increasing the Zr contents. The largest porosity about 27.53% could be obtained at the SrCe0.6Zr0.4O3-δ ceramics sintered at 1500oC for 2 h. Meanwhile, a flat HTM with porous supporting layers of SrCe0.6Zr0.4O3-δ and SrZrO3 was fabricated by constrained sintering. Therefore, the SrCe0.6Zr0.4O3-δ ceramic is suggested to be a potential support layer material without pore former addition and complex sintering process for HTM and hydrogen purification applications.
Second, according the published result of P+-SOFC research, Ba0.8Sr0.2Ce0.6Zr0.2 InxY0.2-xO3-δ proton-conducting oxides are prepared using a solid state reaction process. The effect of indium contents on the microstructures, chemical stability, electrical conductivity, and sintering ability of these Ba0.8Sr0.2Ce0.6Zr0.2InxY0.2-xO3-δ oxides were systemically investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and two probe conductivity analysis. A dense microstructure Ba0.8Sr0.2Ce0.75In0.05Y0.2O3-δ oxide can be prepared by sintering at 1450°C for 4 h which decreased about 200°C sintering temperature. Meanwhile, the optimum conductivity of Ba0.8Sr0.2Ce0.75In0.05Y0.2O3-δ oxide is 0.011 S cm-1 measured at 800°C. In order to enhance the performance of proton-conducting solid oxide fuel cell, the electrolytes and anodes were further improved by modifying the fabrication process. In this study, the laminated electrolyte of Ba0.8Sr0.2Ce0.75In0.05Y0.2O3-δ and anode layers which fabricated by tape casting and co-sintering. The sintered half-cell coated with Pt paste as cathode was prepared for anode supported electrolyte single cell. The effect of NiO contents on the microstructures, surface area, and electric conductivity of these Ni-Ba0.8Sr0.2Ce0.6Zr0.2Y0.2O3-δ anode materials were systemically investigated by tuning the optimum combination of NiO and electrolyte for fabricating the anode materials. The porous structure for the anode substrates not only provide the mechanical strength to the fuel cells, but also allow the fuel gases flow to the electrolyte membrane. On the other hand, the results of cell performance reveal that the powder density of the single cell increases two times with decreasing the thickness of electrolyte layer from 60 m to 20 m. The power density of single cell reaches to 314.2, 259.5, and 150 mW cm-2 at 800, 700, and 600°C, respectively. In this study, the reducing electrolytes process is helpful for proton-conducting solid oxide fuel cells applications.
Therefore, the anode supported proton-conducting electrolyte solid oxide fuel cells were fabricated and evaluate their performance and stability in H2/CO syngas with different ratio of hydrogen (H2), carbon monoxide (CO) fuels was investigated in this study. It was found that inceasing the CO-containg feed streams with decreasing hydrogen gas would gradually degrade the performance of the P+-SOFC. In addition, the carbon deposition will block the nickle catalyst reaction in the anode during the cell testing in CO-containg fuels surrroundings. Therefore, it was showed that the Ba0.8Sr0.2Ce0.75In0.05Y0.2O3-δ ceramic of P+-SOFC possess not only high protonic conductivity but also good chemical stability. In the future, we will try to fabricate the planar P+-SOFC single cell and P+-SOFC stack interconnect components. Moreover, we expect to establish the process window of fabricating the high performance anode supported P+-SOFC single cells. |
