發(fā)布時間：2018-04-27 16:56

  本文選題：固體氧化物燃料電池 + 鈣鈦礦結構陰極材料��； 參考：《大連理工大學》2015年博士論文

【摘要】：固體氧化物燃料電池(SOFC)是一種將化學能轉變?yōu)殡娔艿母咝ЬG色能源技術,將SOFC工作溫度由-1000℃高溫降低至500℃-800℃中溫范圍,即研發(fā)中溫SOFC,是目前該領域的重要發(fā)展方向。工作溫度的降低有利于降低SOFC制備與運行成本、提高電池結構與性能穩(wěn)定性進而延長使用壽命,但同時也帶來陰極、電解質、陽極等組元材料的性能下降問題,特別是,由于陰極氧還原反應活化能較大,導致陰極極化阻抗隨溫度降低急劇增大,成為中溫SOFC輸出功率的主要限制因素。因此,研發(fā)綜合性能優(yōu)良的陰極材料對于促進SOFC中溫化發(fā)展、應用具有重要意義。鉆基鈣鈦礦結構氧化物是重要的中溫SOFC陰極候選材料,具有高電子-離子混合電導率和高氧還原催化活性優(yōu)勢,但普遍具有過高的熱膨脹系數(TEC),與常用電解質材料Gd0.1Ce0.9O1.95 (GDC). Sm0.1Ce0.9O1.95 (SDC)、La0.8Sr0.2Ga0.83Mg0.17O3-δ(LSGM)等存在TEC失配問題,將導致SOFC在高溫燒結制備與長期運行過程中的結構開裂與性能惡化。因此,降低TEC值、提高與電解質材料的TEC匹配從而提高SOFC的結構與性能穩(wěn)定性,是目前鈷基鈣鈦礦陰極材料亟待解決的關鍵問題。鈷基鈣鈦礦氧化物TEC高的本質原因來自于B位Con+(n=2、3、4)離子的還原變價以及電子自旋態(tài)的改變,以價態(tài)穩(wěn)定的過渡金屬離子部分取代Con+離子能夠有效降低材料的TEC值；另外,在鈷基鈣鈦礦氧化物中加入一定量TEC值小的其它組分構成復合陰極材料是降低TEC值的又一可行途徑；并且,這兩種TEC改性途徑將同時伴隨陰極電學與電化學性能的改變。本論文選擇立方鈣鈦礦結構La0.5Ba0.5CoO3-δ與層狀鈣鈦礦結構PrBaCo2O6-δ氧化物做為研究對象,通過進行B位離子摻雜與復合材料制備兩種途徑,進行該陰極材料性能優(yōu)化研究。本論文的主要研究內容與實驗結果如下：1、采用sol--l方法合成了B位Fen+(n=3、4)摻雜(LBCF-y,y=0.1-0.9)系列樣品,并對LBCF-y的氧含量、化學缺陷、熱膨脹行為、電學和電化學性能進行了研究分析。XRD結果表明：Fen+摻雜量y=0.1-0.7時,LBCF-y為立方鈣鈦礦結構純相,y高于0.7則出現雜相,并且,隨Fen+摻雜量增大,LBCF-y發(fā)生晶格膨脹；室溫碘滴定測試結果表明：Fen+摻雜量越大,LBCF-y的氧含量與B位離子平均價態(tài)越高,當y=0.1-0.3時,晶格中B位離子主要以Fe4+、Co4+、Co3+形態(tài)存在,而對于y=0.5-0.7的樣品,B位離子則主要以Fe4+、Fe3+、Co3+形態(tài)存在；在空氣中20-1000-溫度范圍內測試了樣品的熱膨脹特性并計算了TEC值,隨著Fen+摻雜量增大,LBCF-y的TEC值呈現先增大后減小趨勢,在y=0.7時TEC最��；利用直流四電極方法測試了LBCF-y空氣中100-850℃C溫度范圍內的電導率,發(fā)現電導率隨溫度的升高先增大后減小,而在相同溫度下,隨Fen+摻雜量增大,LBCF-y電導率逐漸降低,但所有樣品電導率滿足SOFC要求；LBCF-y TEC和電導率的變化規(guī)律與其化學缺陷隨Fen+摻雜濃度的變化有關；測試了LBCF-y陰極在650-800℃C溫度下與不同氧分壓氣氛中的交流阻抗譜特性,并探討了電極反應機制,結果表明：隨B位Fen+摻雜量增大,L BCF-y陰極極化阻抗有所增大,主要是由于Fen+摻雜降低了LBCF-y中的氧空位濃度,不利于LBCF-y陰極的高頻氧離子體擴散；但是,所有LBCF-y (y=0.1-0.7)樣品650℃下比表面極化阻抗(ASR)均小于01 Ω·cm2,具有高氧還原催化活性。2、采用sol-gel方法合成了B位Sc3+摻雜PrBaCo2-xScxO6-δ (PBCS-x, x=0.00-1.00)系列粉體,研究了Sc3+摻雜對樣品的相結構、氧含量、化學缺陷、熱學行為、熱膨脹行為、電學及電化學性能等的影響。結果表明：隨Sc3+摻雜量增大,樣品發(fā)生相結構轉變,低Sc3+摻雜量(x≤0.20)時,PBCS-x為四方相雙層鈣鈦礦結構,SC3+摻雜量x=0.30-0.40時,為二元復合相,Sc3+摻雜量x=0.50-0.90時,為簡單立方相鈣鈦礦結構,而Sc3+摻雜量過高(x=0.1)則出現少量雜相；碘滴定結果表明：隨著Sc3+摻雜量增大,PBCS-x的氧含量減小,氧空位濃度增大,Co4+離子含量減小,該化學缺陷的變化是SC3+摻雜導致PBCS-x結構與性能變化的本質原因；隨Sc3+摻雜量增大,PBCS-x TEC逐漸減小與電解質材料TEC匹配性提高,而電導率逐漸減��；PBCS-x/GDC/PBCS-x對稱電池交流阻抗譜測試結果表明：Sc3+摻雜取代部分B位Co離子使PBCS-x陰極的電化學催化活性顯著增強,陰極ASR隨Sc3+摻雜量增大而減小,在所研究的PBCS-x系列樣品中,Sc3一摻雜量x=0.5樣品具有最好的電化學性能,600℃C時其ASR值僅為0.123 Ω·cm2,是一種具有應用前景的新型中溫SOFC陰極材料。3、采用sol-gel方法制備了Pr0.83BaCo1.33Sc0.50δ-0.17PrCoO3(PBCS-0.17PCO)復合納米粉體中溫SOFC陰極材料,對其相結構、熱膨脹系數、電學與電化學性能進行了研究,并與同成分單相陰極材料PrBaCo1.5Sco.506-δ進行了對比分析。XRD測試結果表明：該復合材料由兩種立方相鈣鈦礦結構氧化物Pr0.83BaCo1.33Sco.5O6-δ與PrCoO3組成,其中PrCoO3含量為17 mo1%；微觀形貌SEM圖表明PBCS-0.17PCO復合樣品具有顆粒尺寸小、粒度均勻、分散性好等的特點；TEC測試結果表明：與PrBaCo1.5Sco.5O6-δ單相陰極相比,PBCS-0.17PCO復合陰極TEC值減小,30-900℃C溫度區(qū)間TEC值為18.4x10-6/℃,與電解質材料的TEC匹配性提高；利用直流四電極方法對樣品在空氣中50-850℃C溫度下的電導率進行了測試,結果表明：PBCS-0.17PCO復合陰極電學行為與PrBaCO1.5Sc0.5O6-δ單相陰極不同,并且在整個測試溫度區(qū)間內復合陰極的電導率相對較小；對稱電池交流阻抗譜測試結果表明：PBCS-0.17PCO復合陰極具有良好的氧還原反應電化學催化性能,在600℃、650℃C、700℃、750℃下的ASR分別為0.127Ω·cm2、0.069Ω·cm2、0.039Ω·cm2、0.026Ω·cm2，且長時間工作性能穩(wěn)定,是一種性能優(yōu)良的新型中溫SOFC復合陰極材料。
[Abstract]:Solid oxide fuel cell (SOFC) is a high efficient green energy technology that transforms chemical energy into electrical energy. It is an important direction in this field to reduce the working temperature of SOFC from -1000 C to 500 C and -800 C medium temperature range, which is an important direction of development in this field. The decrease of working temperature is beneficial to reduce the cost of SOFC preparation and operation and improve electricity. The stability of the pool structure and performance further prolongs the service life, but it also brings the performance decline of the cathode, electrolyte, anode and other component materials, especially, because the activation energy of the cathode oxygen reduction reaction is larger, the cathodic polarization impedance increases sharply with the temperature decrease, which is the main limiting factor of the output power of the medium temperature SOFC. The cathode materials with excellent comprehensive properties are of great significance for promoting the development of SOFC medium temperature. The drilling based perovskite structure oxide is an important medium temperature SOFC cathode candidate material, with high electron ion mixed conductivity and high oxygen reduction catalytic activity, but high thermal expansion coefficient (TEC) and common electrolyte materials are widely used. The Gd0.1Ce0.9O1.95 (GDC), Sm0.1Ce0.9O1.95 (SDC), La0.8Sr0.2Ga0.83Mg0.17O3- Delta (LSGM) and other TEC mismatches will lead to the structural cracking and performance deterioration of SOFC during the high temperature sintering and long-term operation. Therefore, the TEC value is reduced and the TEC matching with the electrolyte material is improved to improve the stability of the structure and performance of SOFC. At present, the key problem of cobalt based perovskite cathode material needs to be solved. The essence of cobalt based perovskite oxide TEC is due to the reduction price of B Con+ (n=2,3,4) ion and the change of electron spin state. The substitution of Con+ ions with the stable transition metal ions in the valence state can effectively reduce the TEC value of the material; in addition, in the cobalt base calcium carbonate, the cobalt base calcium oxide can be effectively reduced. It is another feasible way to reduce the TEC value by adding some other components with a certain amount of TEC value in the titanium oxide oxide. Moreover, the two TEC modification routes will be accompanied by the change of cathode and electrochemistry. This paper chooses the cubic perovskite structure La0.5Ba0.5CoO3- Delta and the PrBaCo2O6- delta oxygen of the layered perovskite structure. In this paper, the main research contents and experimental results are as follows: 1, the B bit Fen+ (n=3,4) doping (LBCF-y, y= 0.1-0.9) series samples were synthesized by sol--l method, and the oxygen content and chemical defects of LBCF-y were studied in this paper. The main contents and the experimental results of this paper were two ways. The thermal expansion behavior, electrical and electrochemical properties have been studied and analyzed by.XRD results. The results show that LBCF-y is a pure phase of cubic perovskite structure and Y is higher than 0.7 when the amount of Fen+ doping is y=0.1-0.7, and the lattice expansion of LBCF-y occurs with the increase of Fen+ doping amount. The test results at room temperature iodine drops show that the greater the doping amount of Fen+, the oxygen content of LBCF-y is found. The higher the average valence state of the B bit ion is, the B ions in the lattice are mainly in the form of Fe4+, Co4+, Co3+ when y=0.1-0.3, while for the samples of y=0.5-0.7, the B bit ions are mainly in Fe4+, Fe3+, Co3+ morphology, and the thermal expansion properties of the samples are measured in the range of 20-1000- temperature in the air and the values are calculated. The TEC value of BCF-y increases first and then decreases, and TEC is minimum at y=0.7. The conductivity of LBCF-y air in the temperature range of 100-850 C is measured by the method of DC four electrode. It is found that the conductivity increases first and then decreases with the increase of temperature, and the conductivity of LBCF-y decreases with the increase of Fen+ doping at the same temperature, but all samples are decreased. The electrical conductivity meets the requirements of SOFC; the variation of LBCF-y TEC and electrical conductivity is related to the change of the chemical defects with the Fen+ doping concentration; the impedance spectrum characteristics of the LBCF-y cathode at 650-800 C at C temperature and the different oxygen partial pressure atmosphere are tested and the electrode reaction mechanism is discussed. The results show that the L BCF-y negative is increased with the B bit Fen+ doping. The increase of polar polarization impedance is mainly due to the reduction of oxygen vacancy concentration in LBCF-y by Fen+ doping, which is not conducive to the diffusion of high frequency oxygen plasma of the LBCF-y cathode. However, all LBCF-y (y=0.1-0.7) samples are less than 01 Omega cm2 at 650 C, and have a high oxygen reduction catalytic activity.2, and B bit S is synthesized by the sol-gel method. C3+ doped PrBaCo2-xScxO6- Delta (PBCS-x, x=0.00-1.00) powders have been used to study the effects of Sc3+ doping on the phase structure, oxygen content, chemical defects, thermal behavior, thermal expansion behavior, electrical and electrochemical properties. The results show that the phase structure transformation of the sample increases with the increase of Sc3+ doping, and the PBCS-x is four when the low Sc3+ doping amount (x < 0.20) is low. In the double perovskite structure, when the SC3+ doping amount is x=0.30-0.40, it is two element composite phase, and when Sc3+ doping x=0.50-0.90, it is a simple cubic perovskite structure, while the Sc3+ doping amount is too high (x=0.1) appears a small amount of heterozygosity. The iodine titration results show that as Sc3+ doping increases, the oxygen content of PBCS-x decreases, the oxygen vacancy concentration increases, Co4+ ion concentration increases. The change in the chemical defect is the essential reason for the change of the structure and properties of PBCS-x with SC3+ doping. With the increase of the doping amount of Sc3+, the PBCS-x TEC decreases gradually with the electrolyte material TEC, and the conductivity gradually decreases, and the AC impedance spectroscopy test results of PBCS-x/GDC/PBCS-x symmetric batteries show that Sc3+ doping takes the place of partial B. The electrochemical catalytic activity of the PBCS-x cathode was significantly enhanced and the cathode ASR decreased with the increase of the doping amount of Sc3+. In the PBCS-x series of samples studied, the Sc3 doped x=0.5 samples had the best electrochemical performance. The ASR value was only 0.123 Omega cm2 at 600 C, and it was a new medium temperature SOFC cathode material.3, which was of the prospect of application. The medium temperature SOFC cathode material of Pr0.83BaCo1.33Sc0.50 Delta -0.17PrCoO3 (PBCS-0.17PCO) composite nano powder was prepared by sol-gel method. The phase structure, thermal expansion coefficient, electrical and electrochemical properties were studied. The comparison of the PrBaCo1.5Sco.506- delta with the single-phase cathode material of the same component was compared and analyzed by.XRD test results. The results showed that the composite material was the composite material. The material is composed of two kinds of cubic perovskite oxide Pr0.83BaCo1.33Sco.5O6- Delta and PrCoO3, of which the PrCoO3 content is 17 mo1%, and the micromorphology SEM diagram shows that the PBCS-0.17PCO composite samples have the characteristics of small particle size, uniform particle size and good dispersibility, and TEC test results show that, PBCS-0.1 compared with PrBaCo1.5Sco.5O6- delta single-phase cathode, PBCS-0.1 The TEC value of 7PCO composite cathode is reduced, the TEC value of C temperature range at 30-900 C is 18.4x10-6/ C, and the TEC matching of the electrolyte material is improved. The conductivity of the sample under the temperature of 50-850 C at 50-850 C in the air is tested by the direct current four electrode method. The results show that the PBCS-0.17PCO composite cathode electrical behavior is not with the PrBaCO1.5Sc0.5O6- delta single-phase cathode. The conductivity of the composite cathode is relatively small in the whole test temperature range, and the AC impedance spectroscopy test of the symmetrical battery shows that the PBCS-0.17PCO composite cathode has a good electrochemical catalytic performance in the oxygen reduction reaction, and the ASR at 650, 700, and 750 is 0.127 Omega. Cm2,0.039 Omega cm2,0.026 Omega at 650, 700 and 750. Cm2, which has long performance and stable performance, is a new type of medium temperature SOFC composite cathode material with excellent performance.

【學位授予單位】：大連理工大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TM911.4

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1 李向楠;B位離子摻雜鈣鈦礦型中溫固體氧化物燃料電池陰極研究[D];大連理工大學;2015年

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本文編號：1811546