本文選題：中溫固體氧化物燃料電池　切入點：B_(1-x)C_xCFN　出處：《吉林大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：能源是社會發(fā)展的基礎(chǔ),傳統(tǒng)發(fā)電系統(tǒng)存在能源利用率低、高污染等諸多缺點,固體氧化物燃料電池(SOFC)具有轉(zhuǎn)化效率高、污染低等諸多優(yōu)點,是基于現(xiàn)有能源供應(yīng)體系下可實現(xiàn)大規(guī)模高效發(fā)電的新能源技術(shù)。SOFC在發(fā)展之初存在操作溫度(YSZ電解質(zhì)操作溫度為1000℃)過高的問題,因而引起材料易老化、成本過高及維護不便等一系列問題。SOFC實用化首先需要解決的問題就是其操作溫度過高的問題,目前目標是把SOFC的操作溫度降到中溫(600-800℃)這一區(qū)間,但降低操作溫度會增大電解質(zhì)的歐姆損失以及陰極的極化損失。隨著新型電解質(zhì)材料的研發(fā),歐姆損失得到降低,降低電解質(zhì)材料的厚度也可以有效降低電解質(zhì)的歐姆損失,近年來薄膜技術(shù)的發(fā)展對解決電解質(zhì)歐姆損失的問題有較大貢獻。因此,提高陰極材料在中溫條件下的性能,即降低陰極材料在中溫條件下的極化損失,提高在中溫條件下的催化活性成為IT-SOFC發(fā)展的關(guān)鍵。本論文旨在通過改進現(xiàn)有陰極材料來提高IT-SOFC的性能。ABO_3型鈷基鈣鈦礦氧化物的A位和B位陽離子可以被其他不同價態(tài)的的陽離子部分地取代,為保持整個體系的電中性而產(chǎn)生氧空位,使其在具有較高的電子導(dǎo)電性的同時具有良好的氧離子導(dǎo)電能力,是IT-SOFC其中一種非常重要的陰極材料。本文以Ba1-x Cax Co0.7Fe0.2Nb0.1O3-δ(BCCFN)陰極材料和BCCFN-SDC電解質(zhì)復(fù)合陰極材料為研究對象,研究了陰極材料包括物相結(jié)構(gòu)、微觀形貌、熱膨脹系數(shù)、半電池阻抗譜和單電池輸出功率等各種特性。通過調(diào)控材料的成分組成,試圖找出能降低陰極材料極化阻抗的配比,探討其作為SOFC陰極材料的可行性,期望可以進一步提高IT-SOFC的性能。主要研究內(nèi)容如下:1.鈷基鈣鈦礦型氧化物Ba Co_(0.7)Fe_(0.2)Nb0.1O3-δ(BCFN)是一種電化學(xué)性能比較好的IT-SOFC陰極材料,其具有優(yōu)秀的電子-離子混合導(dǎo)電能力。但其存在與電解質(zhì)熱匹配性較差的缺點,為了進一步提高此材料作為IT-SOFC陰極材料的性能,有必要降低其熱膨脹系數(shù),提高其與電解質(zhì)材料的熱匹配性,保證其在工作溫度下的穩(wěn)定性,降低其在中溫(600-800 o C)下的極化阻抗,提升電極性能,從而提高單電池的最大功率密度。因此,我們選擇在A位摻Ca~(2+)試圖提高其作為IT-SOFC陰極材料的性能。采用固相法合成Ba1-xCax Co0.7Fe0.2Nb0.1O3-δ(B1-x Cx CFN,x=0.0,0.1,0.2,0.3,0.4)陰極材料,通過XRD衍射普分析發(fā)現(xiàn),B1-xCx CFN陰極材料在1000 oC燒結(jié)10 h后,形成了單相的立方鈣鈦礦結(jié)構(gòu)。通過分析電鏡圖片,B0.9C0.1CFN形成了疏松多孔的微觀結(jié)構(gòu),并且與SDC電解質(zhì)結(jié)合良好,沒有出現(xiàn)剝落跡象。A位摻雜Ca~(2+)后,降低了陰極材料的熱膨脹系數(shù)。半電池阻抗分析發(fā)現(xiàn)BCFN材料A位摻雜Ca~(2+)降低了陰極材料的極化電阻(RP),當A位摻Ca~(2+)的摻雜量為x=0.1時,RP值最小,在800 o C時,B0.9C0.1CFN半電池的極化電阻值為0.4458Ωcm2。Ca~(2+)的適當摻雜使B位離子從+3價升到+4價,使B3+-O-B4+小極化子的濃度提高,降低了材料的極化阻抗,電化學(xué)性能得到提高,當進一步提高Ca~(2+)的摻雜量時,B位離子從+3價升到+4價的離子數(shù)過多,+3價離子數(shù)減少,使材料的極化阻抗增加。單電池功率密度測試發(fā)現(xiàn)結(jié)構(gòu)為B1-xCx CFN/SDC/Ni0.9Cu0.1-SDC的單電池隨著陰極A位Ca~(2+)的摻入,功率密度變大,當Ca~(2+)的含量x為0.1時,以B0.9C0.1CFN為陰極材料的單電池具有最好的輸出功率密度曲線,在800o C的最大功率密度達到338m Wcm-2,當進一步提高A為Ca~(2+)的摻雜量時,單電池的功率密度開始下降,B0.9C0.1CFN陰極表現(xiàn)出最好的電化學(xué)性能。2.B_(0.9)C_(0.1)CFN陰極材料表現(xiàn)出了優(yōu)秀的綜合性能,成為一種有希望的IT-SOFC陰極材料。為了進一步增強材料的電化學(xué)性能以及與SDC電解質(zhì)的匹配性,提高氧的還原反應(yīng)速率,我們對B0.9C0.1CFN材料進行了改進研究,將B0.9C0.1CFN(BCCFN)與SDC電解質(zhì)材料復(fù)合制成復(fù)合陰極材料,可望進一步降低其熱膨脹系數(shù),改善陰極材料的氧還原反應(yīng)過程,提高其性能。研究結(jié)果表明,1000 o C燒結(jié)10h后,BCCFN與SDC間保持各自的相結(jié)構(gòu),化學(xué)相容性良好。電鏡圖片顯示BCCFN-30SDC表現(xiàn)了更低的空隙率及更小的顆粒尺寸,這有利于形成連續(xù)的SDC離子擴散通道和連續(xù)的BCCFN電子導(dǎo)電通道。復(fù)合SDC是一種可以有效降低陰極材料的熱膨脹系數(shù)的方法,使其熱膨脹系數(shù)更接近于SDC電解質(zhì),提高了陰極材料與電解質(zhì)材料的熱匹配性。BCCFN陰極材料復(fù)合SDC可以提高陰極材料的電化學(xué)性能,BCCFN-x SDC(x=0,20,30,40)復(fù)合陰極材料半電池阻抗測試表明,隨SDC電解質(zhì)的復(fù)合量的增加,陰極極化電阻(Rp)隨之而減小,當復(fù)合含量x=30wt%時,極化電阻達到最小值,在800o C時Rp值達到0.2984Ωcm2,當SDC含量進一步增多時,BCCFN相連續(xù)性下降,影響了陰極氧的還原反應(yīng),使極化電阻反而增大。以BCCFN-x SDC為陰極的電解質(zhì)支撐的結(jié)構(gòu)為BCCFN-x SDC|SDC|Ni0.9Cu0.1-SDC的單電池的測試結(jié)果表明,復(fù)合SDC的含量為30wt%時,單電池表現(xiàn)出更優(yōu)的功率密度曲線,800 o C時以BCCFN-30SDC為陰極的單電池最大功率密度達到351 m Wcm-2,這表明BCCFN-30SDC是一種發(fā)展前景良好的IT-SOFC陰極材料。
[Abstract]:Energy is the foundation of social development, has low energy utilization of traditional power system, high pollution and many other shortcomings of solid oxide fuel cell (SOFC) has the advantages of high conversion efficiency, low pollution, high efficiency of power generation is to achieve large-scale new energy technology.SOFC operating temperature at the beginning of the development of existing energy supply system based on the (the operation of YSZ electrolyte temperature of 1000 DEG C) high, and easy material aging, high cost and inconvenient maintenance of a series of practical problems in.SOFC to solve the first problem is that the operating temperature is too high, the current goal is to SOFC operating temperature to drop in temperature (600-800 DEG C) this interval. But the lower operating temperature will increase the electrolyte ohmic losses and cathode polarization loss. With the development of new electrolyte materials, ohmic loss can be reduced, the reduction of electrolyte material thickness It can effectively reduce the ohmic loss of electrolyte, in recent years the development of thin film technology to solve the problem of electrolyte ohmic losses have a greater contribution. Therefore, to improve the performance of cathode materials in temperature, which reduce the polarization loss of cathode material in the temperature, in high temperature catalytic activity become the key to the development of IT-SOFC. The purpose of this paper is to improve the existing cathode materials to improve the performance of.ABO_3 type cobalt oxides IT-SOFC A and B can be replaced by other cations of different valence cations in part, to keep the whole system of electrically neutral and oxygen vacancies, which has good conductivity of oxygen ion the higher electronic conductivity at the same time, IT-SOFC is one kind of cathode material is very important. This paper takes Ba1-x Cax Co0.7Fe0.2Nb0.1O3- 8 (BCCFN) and BCCFN-S cathode materials DC electrolyte composite cathode material as the research object, research on the cathode materials including phase structure, microstructure, thermal expansion coefficient, various characteristics of half cell impedance spectroscopy and single cell output power. By adjusting the material composition, trying to find out the material can reduce the cathodic polarization impedance ratio, to explore its feasibility as SOFC cathode material and look forward to further improve the performance of IT-SOFC. The main contents are as follows: 1. cobalt based perovskite type oxide Ba Co_ (0.7) Fe_ (0.2) Nb0.1O3- 8 (BCFN) is a kind of electrochemical performance of IT-SOFC cathode material is better, it has excellent electron ion conductivity. But the existence of mixed electrolyte matching and heat of the poor, in order to further improve the material properties of IT-SOFC as cathode material, it is necessary to reduce the thermal expansion coefficient, increase the heat and electrolyte materials matching, ensure the Stability at the working temperature, reduce the temperature in the (600-800 o C) polarization impedance of the electrode to enhance performance, thereby increasing the maximum power density of the single cell. Therefore, we chose A doped Ca~ (2+) to improve the performance of IT-SOFC as cathode material synthesized by solid phase method. Ba1-xCax Co0.7Fe0.2Nb0.1O3- Delta (B1-x Cx CFN, x=0.0,0.1,0.2,0.3,0.4) cathode materials by XRD diffraction analysis showed that the general B1-xCx, CFN cathode materials sintered at 1000 oC after 10 h, the formation of single phase cubic perovskite structure. Through the analysis of electron microscope images, B0.9C0.1CFN formed a micro porous structure, and SDC electrolyte with good, no peeling off signs of.A doped with Ca~ (2+), cathode material coefficient of thermal expansion is reduced by half. The cell impedance analysis showed that the BCFN material A doped with Ca~ (2+) to reduce the polarization resistance of the cathode material (RP), when the A doped Ca~ (2+) The doping amount is x=0.1, the minimum RP value at 800 o, C, B0.9C0.1CFN half cell polarization resistance value of 0.4458 ohm cm2.Ca~ (2+) the appropriate doped B ions from the +3 price rose to +4 price, the concentration of B3+-O-B4+ small polaron increase, reduce the polarization resistance of materials, electrochemical performance when improved, further improve the Ca~ (2+) doping, B ions from the +3 ion +4 price price to rise to excessive number of +3 ions decreased, the polarization resistance of materials increased. Single cell power density test showed that the structure is a single cell B1-xCx CFN/SDC/Ni0.9Cu0.1-SDC with A Ca~ (2+) cathode the incorporation of power density change, when Ca~ (2+) the content of X is 0.1, the single battery cathode material with B0.9C0.1CFN as the output power density curve with the best, the maximum power density in 800o C to 338m Wcm-2, when Ca~ further improve A (2+) doping amount, single cell the The power density began to decline, B0.9C0.1CFN cathode showed best electrochemical performance of.2.B_ (0.9) C_ (0.1) CFN cathode material shows excellent performance, has become a promising cathode materials for IT-SOFC. In order to further enhance the electrochemical performance of the material and the compatibility with the SDC electrolyte, improve the oxygen reduction reaction rate. We improved the study of B0.9C0.1CFN materials, B0.9C0.1CFN (BCCFN) and SDC electrolyte material made of composite cathode materials, is expected to further reduce the coefficient of thermal expansion, improve the cathode oxygen reduction reaction process, improve its performance. The results show that the 1000 o C 10h BCCFN after sintering, and SDC phase structure the chemical compatibility is good. Electron microscopy images showed that BCCFN-30SDC showed the particle size and smaller porosity lower, which is conducive to the formation of SDC ion channel and continuous diffusion 榪炵畫鐨凚CCFN鐢?shù)瀛愬鐢?shù)閫氶亾.澶嶅悎SDC鏄竴縐嶅彲浠ユ湁鏁堥檷浣庨槾鏋佹潗鏂欑殑鐑啫鑳，

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