固態氧化物燃料電池陰極 La0.8Sr0.2Mn1?xRuxO3之製作與特性研究 ; Synthesis and properties of La0.8Sr0.2Mn1?xRuxO3 as cathodes for solid oxide fuel cells

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题名:	固態氧化物燃料電池陰極 La0.8Sr0.2Mn1?xRuxO3之製作與特性研究;Synthesis and properties of La0.8Sr0.2Mn1?xRuxO3 as cathodes for solid oxide fuel cells
作者:	李岱陽;Tai-Yang Lee
贡献者:	材料科學與工程研究所
关键词:	電化學;氧還原反應;催化劑;陰極;固態氧化物燃料電池;Electrochemistry;ORR;Catalyst;Cathode;SOFC
日期:	2011-08-22
上传时间:	2012-01-05 12:24:39 (UTC+8)
摘要:	本論文依化學共沉法製備含不同釕組成之La0.8Sr0.2Mn1−xRuxO3 (其中x=0、0.25、0.5、0.75、1.0)固態氧化物，探討其作為燃料電池陰極觸媒之可行性。實驗時，調整釕與錳的比例、前驅粉體的煆燒溫度等因素，研究其形成觸媒時的結晶性質、表面形貌、比表面積、電化學性質等，以評估作為燃料電池陰極的可行性。利用場發射電子顯微鏡(FE-SEM)、X光能量散佈儀(EDS)觀察觸媒粉體表面形貌與元素，X光繞射光譜儀(XRD)鑑定粉體與觸媒的結晶結構，BET氮氣吸附比表面積測試儀(BET)分析觸媒比表面積，並以感應耦合電漿發射光譜 (ICP-OES)分析含有元素種類與比例。檢視釕與錳的比例、前驅粉體煆燒溫度等變化對所製觸媒在形貌、成分、晶體構造、比表面積比等之影響，以及作為電池陰極之電化學行為之差異。電化學測試包含I-V與電化學阻抗頻譜(EIS)，分析電池之歐姆阻抗、電荷轉移阻抗與質傳阻抗。結果顯示: 0.2 M硝酸前驅溶液經1 M氫氧化鈉滴定共沉後，於1000℃煆燒之粉體，製成電池陰極，由FE-SEM觀察，顯示為多孔結構，其XRD繞射圖譜含有鑭(La)、鍶(Sr)、錳(Mn)、釕(Ru)之氧化物且為具鈣鈦礦結構之La0.8Sr0.2Mn1−xRuxO3。隨著釕比例逐漸增加而使氧化物由鈣鈦礦的三方結構轉變為正交結構，由BET數據顯示：此陰極的比表面積隨釕添加量增加而降低。由全電池I-V極化曲線分析與電化學交流阻抗分析(EIS)可得知劑量比在0.25時，可有效降低氧氣還原反應(ORR)所造成的阻抗，全電池性能較高。 Chemical co-precipitation method was used to prepare the precursor which could be calcined to form La0.8Sr0.2Mn1−xRuxO3 (x = 0, 0.25, 0.5, 0.75, 1.0) as the cathode catalyst materials of the solid oxide fuel cells (SOFC). The effects of stoichiometric ratio between Ru/Mn and calcination temperature on the morphology, crystalline structure of the catalysts and on their specific surface area and cathodic behavior used in SOFC were of interest. Examination through field emission scanning electron microscope (FE-SEM) equipped with energy dispersive x-ray analysis (EDS), we could compare the morphology and composition for the powders and catalysts. Analysis by x-ray diffraction (XRD), we could distinguish the crystal structures between different types of catalysts. The specific surface area for different catalysts was measured by means of BET adsorption. The specific surface area was derived from different powders varying in Ru/Mn ratios sintered at various temperatures under various ratios of Ru/Mn. Chemical co-precipitation was carried out by titration a 0.2 M nitrate solution of precursors with 1.0 M sodium hydroxide solution. After filtration, the precursors were dried and calcined at 1000℃ for 5 h. Examination by FE-SEM depicted the calcined oxides are in porous morphology. Through analysis with XRD, we identified the calcined oxides as perovskite structure in which the chemical formula could be La0.8Sr0.2Mn1−xRuxO3 where x varies depending on the ratios of Ru/Mn. The perovskites may shift their crystal structure from trigonal to orthorhombic with increasing x from 0 to 1.0. The specific surface area of the calcined oxides decreases with increasing the Ru-concentration by checking the BET data. After making the calcined oxides as the cathode catalysts in a single cell, I-V polarization test and electrochemical impedance were conducted to evaluate the electrochemical performance. It was found that performance is the best for the catalyst with x equivalent to 0.25 (i.e., La0.8Sr0.2Mn0.75Ru0.25O3) that with the lowest impedance for the oxygen reduction reaction (ORR).
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