管狀固體氧化物燃料電池陽極支撐體的制備與電化學性能表征

1、管狀固體氧化物燃料電池陽極支撐體的制備與電化學性能表征        【中文摘要】固體氧化物燃料電池(SOFC)是一種新型的發(fā)電裝置,具有能量轉(zhuǎn)換效率高、環(huán)境污染小、燃料的適應性強等優(yōu)點,在當今全球能源短缺、能源供給形式相對單一以及環(huán)境污染日益嚴重的形勢下被寄予厚看。隨著SOFC技術(shù)的不斷發(fā)展和完善,其貿(mào)易化進程不斷推進。面對傳統(tǒng)的SOFC在高溫(1000°C左右)下運行所帶來的材料技術(shù)和本錢方面的題目,以及氫氣作為SOFC燃料的局限性,研究職員深刻地熟悉到降低電池的本錢和使用碳氫化合物作為燃料對于固體氧

2、化物燃料電池的貿(mào)易化具有重要意義。降低本錢可以通過開發(fā)新的電池制備技術(shù)和降低運行溫度來實現(xiàn)。降低電池運行溫度就需要進步電解質(zhì)材料的電導率、降低電解質(zhì)厚度和進步電極性能。通過電極結(jié)構(gòu)的優(yōu)化、修飾和開發(fā)新型電極材料,進而獲得高催化活性和抗積碳的陽極,則是SOFC使用碳氫燃料的必要條件。鑒于此,本論文的出發(fā)點就是探索SOFC的低本錢制備技術(shù),并且制備出單電池對其顯微結(jié)構(gòu)、輸出性能和長期穩(wěn)定性進行研究。另外,采用新技術(shù)制備出的管狀陽極支撐體的孔隙率可以在大范圍內(nèi)進行調(diào)整,使后續(xù)的表面修飾成為可能。陽極經(jīng)過修飾后的電池在通進氫氣和甲烷時的穩(wěn)定性測試和抗積炭題目得到進一步研究。論文的第一章簡單先容了SOF

3、C的操縱原理,綜述了SOFC各關鍵材料,重點討論了SOFC的結(jié)構(gòu)與制備和以碳氫燃料相關的陽極材料的最新研究進展。在概述了SOFC的發(fā)展現(xiàn)狀和趨勢的基礎上,確立了本論文的研究目標和研究內(nèi)容。關鍵材料的制備和電池*是SOFC技術(shù)的基礎,對電極、電解質(zhì)以及電池進行精確和有效的評價可以幫助我們選擇合適的材料和綜合評估SOFC的性能。因此第二章就本論文探索的制備工藝,燒結(jié)工藝和評價方法進行具體的先容,總的來講分為電池陽極支撐體的制備和單電池的制作。管狀陽極支撐體是采用注凝成型工藝(gel-casting)制備的Ni/YSZ金屬陶瓷。在本論文中,我們利用注凝成型技術(shù)把陶瓷粉末和有機單體等制成低粘度高固相含

4、量的濃懸浮體,然后在溫度和引發(fā)劑的作用下,使懸浮體中的有機單體交聯(lián)聚合成三維網(wǎng)狀結(jié)構(gòu),從而使懸浮體原位固化成型。近乎實現(xiàn)了凈尺寸成型復雜外形的陽極支撐體,并且支撐體的強度足夠,Ni和YSZ兩相以及氣孔分布均勻公道。具體研究了石墨作為造孔劑其添加量對支撐體的燒結(jié)收縮率和孔隙率的影響。單電池制作方法為陽極過渡層(dip-coating工藝)-電解質(zhì)(dip-coating工藝)-陰極(涂覆工藝)。燒結(jié)工藝也是電池制備的關鍵。本論文采用的燒結(jié)工藝為陽極支撐體生坯預燒1150 oC-陽極及過渡層共燒1200 oC左右-陽極和電解質(zhì)共燒1350 oC。表征方法有交流阻抗譜技術(shù)及激光粒度分布儀、掃描電子顯

5、微技術(shù)(SEM)等。論文第三章先容了在以氫氣為燃料氣的情況下,陽極支撐體浸漬SDC對電池輸出性能的影響。添加質(zhì)量分數(shù)為15%的石墨使支撐體在還原前孔隙率接近30%,SDC的最佳浸漬量為273 mg/cm3,電池的極化阻抗降低了47%,最大輸出功率密度進步了60%在700 oC時。電池分別在700 oC、750 oC和800 oC進行了I-V和I-P測試。電池的開路電壓接近理論電壓,并且浸漬的管狀電池在800 oC時的最大輸出功率密度達到了550 mW/cm2。電池在800 oC長期運行很穩(wěn)定。電池測試過后的電鏡圖片表明電極與電解質(zhì)接觸良好,電解質(zhì)很致密。另外,對浸漬的納米級SDC顆粒在電池還原

6、和測試過程中的形貌變化進行了具體討論。生物質(zhì)能是一種潔凈的可再生能源,它占居了世界總能源的13%。生物質(zhì)氣通過SOFC發(fā)電,能夠進步能源轉(zhuǎn)換效率,并降低污染物排放量,順應了世界能源體系的發(fā)展方向。此時,開發(fā)高活性抗積碳陽極就成為關鍵技術(shù)題目之一。論文第四章先容了在以甲烷為燃料氣的情況下,管狀陽極支撐體浸漬SDC后的抗積炭性能。以SDC浸漬8次的電池為研究對象,對電池在直接通進甲烷作為燃料的穩(wěn)定性能進行測試和氫氣-甲烷不斷切換下的循環(huán)性能進行測試。用SDC修飾的陽極在通進甲烷燃料氣的情況下可以長期穩(wěn)定的運行,而沒有修飾的電池在24小時內(nèi)性能衰減近50%。浸漬的SDC有效地抑制了積炭的發(fā)生。氫氣和

7、甲烷循環(huán)測試表明燃料氣的切換對電池的穩(wěn)定性沒有什么影響,但是在通進相同流量的燃料氣時,通甲烷時的功率密度明顯高于通氫氣時的功率密度。');【Abstract】 Solid oxide fuel cell (SOFC) is a new energy conversion device which has been held the highest hopes because of their high efficiency, little pollution and flexibility in the choice of fuels, especially at the time w

8、hen the current energy structure is not reasonable and the environment pollution becomes more and more serious. As a new promising technique, it will fulfill the increasing need of electricity, improve the current energy structure, and impact the whole world environment actively in the near future.

9、With the development of SOFCs and its commercialization implementation, there are two main issues for SOFCs so far that are material technique and high cost problems related to high temperature operation ( 1000 oC) as well as the limit for hydrogen fuels with respect to efficiency, storage and trans

10、portation, etc. It is crucial, therefore, to reduce the cost and use hydrocarbon as the fuel for SOFCs. Looking for the efficient and cost-effective fabrication techniques and decreasing the thickness of electrolyte, developing novel electrolyte with higher ionic conductivity and new electrodes with

11、 higher performance are the major approaches to lower the cost. For direct utilization of hydrocarbon, it is necessary to fabricate the highly catalytic anode with the capability to avoid carbon deposition by modifying and optimizing the electrode microstructure or developing new materials.This thes

12、is aims to lower the cost and study the microstructure and electrochemicial performance of cells. In addition, the anode substrates prepared by the gel-casting technique have a large range of porosity, which make for the modification of the anode. The performance of the modified cell with hydrogen a

13、nd methane as fuels is studied.Chapter 1 reviews the working principle, materials for SOFC, especially main points of anode developments with methane as fuel. Proposal on the thesis work is also presented in this chapter.Preparation of key component materials and cells is basal technique in developi

14、ng SOFCs. Accurate and efficient characterization is critical in selecting suitable materials as well as overall evaluation of the performance of SOFC. Chapter 2 gives detail information about gel-casting technique, co-firing process and characterization technique. In our work, the ceramic powders a

15、nd organic materials were made into stable suspension with high solid loading. Monomers polymerized into three-dimensional structure and made the suspension into green body at 80 oC. The gelcasting process is more cost-effective and flexible for fabricating complex three-dimensional ceramic parts, a

16、nd also easy to scale up. The anode substrate which is uniform has enough strength. Effect of graphite addition on the porosity and sintering shrinkage of the substrate was studied. The single cell was fabricated by gel-casting, dip-coating and slurry-coating process. Firing process was 1150 oC(anod

17、e substrate)-1200 oC(anode substrate and interlayer)-1350 oC(anode and electrolyte co-firing). Characterization techniques are Ac impedance, laser granularity distributing analysis, scanning electron microscope (SEM) technique etc.In chapter 3, effect of SDC on the performance of cell with hydrogen

18、fuel was studied. Porosity of anode substrate before reduction was about 30% with 15% graphite addition, and the optimum SDC loading is 273 mg cm-3 after 6 repeat times of the impregnation cycle in our experiments. The peak power density of the cell was increased by about 60% and the area specific resistance (ASR) decreased by about 47% at 700 oC, compared with the unmodified cells. Performance of cell was tested at 700 oC, 750 oC and 800 oC. Results indicated that OCV(open current voltage) of cell reached nearly to the theory value. Electrode attached to the electrolyte well, and t