1、利用電導弛豫方法研究燃料電池陰極材料利用電導弛豫方法研究燃料電池陰極材料小組小組成員成員：謝云，史鼐，孫樂，陳明龍，黃晉，馬致遠。報告人報告人：史鼐Outline:SOFC背景介紹應用舉例電導弛豫方法及影響因素總結O-SOFC示意圖示意圖P-SOFC示意圖示意圖燃料電池陰極反應燃料電池陰極反應La0.6Sr0.4Co0.2Fe0.8O3-d表面氧交換表面氧交換 k(cm s-1)內(nèi)部氧擴散內(nèi)部氧擴散 D(cm2s-1)傳統(tǒng)測量方法：兩端子法（伏安法）傳統(tǒng)測量方法：兩端子法（伏安法）四端子法測電導率四端子法測電導率接觸點和導線電阻不可接觸點和導線電阻不可忽略，尤其對電阻較小的材料，測量不準確忽略

2、，尤其對電阻較小的材料，測量不準確四端子法測量電導率四端子法測量電導率四端子法測電阻示意圖四端子法測電阻示意圖Fick第二定律：22CCDtx0( ,0)C xC00 xCx (, )xlCDk Cl tCxECR理論基礎理論基礎其中其中l(wèi)為最小心樣品尺寸的一半為最小心樣品尺寸的一半定義復合函數(shù)定義復合函數(shù),( )T(t)F x tC x tCX x（） （）22FFDtx邊界條件為：邊界條件為：0( ,0)F xCC00 xFx(, )xlFDkFl tx通過分離變量，可得：XTXDT 0XX(0)0X( )( )DX lkX l0TD T（1）（2）邊界條件：討論取值只有當0時滿足，解得代

3、入邊界條件可得 20C tanklD 12cossinXCxCx 令令l tanlkD 有有最后代入函數(shù)并化簡得最后代入函數(shù)并化簡得20n214(C -C )sinC(x,t)-Ccosexp()sin2nnnnnDxtll 。（1） 即 時，若令 ，則 ，可得 （1） 即 時，若令 ，則 ，可得 0lkD/lD k/clD kcllt00C -C1 exp()C -Cktl 根據(jù)質(zhì)量守恒及缺陷平衡方程可得則 此時材料電導率僅與時間t有關，與 樣品內(nèi)位置x無關，可認為樣品電導率均勻分布( )(0)( )(0)( )(0)( )(0)toohhoohhMC tCC tCtMCCCC )1 exp

4、()tktl 表面擴散控制表面擴散控制（2） 即 時， lkD cll2t020C -C)81exp()C -C4tDtl （3） 時， tannnlkD cll22t0n2210C -C4sin1exp()C -Csin2nnnnnDtl 體擴散控制體擴散控制雙重控制雙重控制理論基礎推廣到三維，歸一化電導弛豫曲線：其中：弛豫曲線與氧分壓關系弛豫曲線與氧分壓關系理論基礎擬合求解擬合求解方法一：方法一：1, 確定確定D,k初步范圍初步范圍2, 求解誤差分布求解誤差分布3, 篩選結果篩選結果(控制步驟）控制步驟）方法二：1, 選定初始D,k值2, 擬合優(yōu)化D,k結果3, 變換初始值多次擬合SFM樣

5、品弛豫曲線的擬合誤差與D、k值的關系Relative asymptotic errors on the estimated k and D獲得獲得D,k值的影響因素值的影響因素擬合影響擬合影響Francesco Ciucci, Solid State Ionics 239 (2013) 2840獲得獲得D,k值的影響因素值的影響因素氣體切換速度氣體切換速度時間時間常數(shù)常數(shù)M. W. den Otter, H. J. M. Bouwmeester, B. A. Boukamp, H. Verweij, Journal of The Electrochemical Society, 148 (20

6、01) J1-J6獲得獲得D,k值的影響因素值的影響因素氧分壓梯度氧分壓梯度對于對于LSCFS. Wang, A. Verma, Y.L. Yang, A.J. Jacobson), Ben Abeles, Solid State Ionics 140 (2001) 125133獲得獲得D,k值的影響因素值的影響因素表面微觀結構表面微觀結構晶粒大小晶粒大小晶界晶界密度（長度）密度（長度）原料分體性質(zhì)原料分體性質(zhì)燒結溫度，時間燒結溫度，時間制備過程制備過程Yunlong Wang, Yao Wang, Changrong Xia, Journal of The Electrochemical S

7、ociety, 159 (9) F570-F576 (2012) ECR應用舉例應用舉例Sr3YCo4O10.5電極材料電極材料Preparation method: SSR (SrCO3, Co3O4, Y2O3)Sintering temperature :9001200Sample sintering temperature: 1180/4hDensity 95%Size: t=1.43mm, w=1.09mm,l=19.72mmElectrical conductivity of Sr3YCo4O10.5 in airMax=550S/cmOxygen vacancies format

8、ionThermal activationA relative electrical conductivity vs. time profile obtained during an ECR experiment at 850 with an oxygen partial pressure switch from 10% to 75% and the corresponding fit Comparing of profiles of relative conductivity. g(t).of Sr3YCo4O10.5 vs. time obtained during ECR experim

9、ents at different temperatures and for switches of oxygen partial pressure from 10% to 75%ECR應用舉例應用舉例Sr3YCo4O10.5電極材料K和初始氧分壓無關，和初始氧分壓無關，和平衡氧分壓有關和平衡氧分壓有關D和氧分壓無關，只和和氧分壓無關，只和溫度有關溫度有關Arrhenius plot of the chemical oxygen diffusion and chemical surface exchange coefficients obtained for Sr3YCo4O10.5 by E

10、CR experimentsECR應用舉例應用舉例Sr3YCo4O10.5電極材料Dependence of chemical surface exchange rate for Sr3YCo4O10.5 on the final oxygen partial pressure during ECR switchesOxygen content in Sr3YCo4O10.5 dependence on oxygen partial pressure in the surrendings and temperature determined by TGA溫度升高，氧濃度減少溫度升高，氧濃度減少

11、ECR應用舉例應用舉例Sr3YCo4O10.5電極材料熱力學熱力學因子因子自擴散自擴散系數(shù)系數(shù)Comparison of oxygen self-diffusion coefficients in Sr3YCo4O10.5 determined by ECR(this work),IEDP/SIMS and molecular dynamicsECR應用舉例應用舉例Sr3YCo4O10.5電極材料ECR應用實例應用實例水對電極材料的影響水對電極材料的影響Schematic representation of cathode reaction in protonic ceramic fuel c

12、ells(PCFCs)Ho-Il Ji, Sung-Min Choi, Kyung Joong Yoon, Ji-Won Son, Byung-Kook Kim, Hae-Weon Lee, Jong-Ho Lee, Solid State Ionics 249250 (2013) 112116Variations in conductivity after the gas was changed from dry air to wet air at 700. Conductivity relaxation curve during a cycle of changes in the gas

13、from wet to dry air and then from dry to wet air in (b) region(i)and region (ii).abcECR應用實例應用實例水對電極材料的影響水對電極材料的影響Conductivity change after the gas was changed from dry air to wet air. Conductivity relaxations upon oxygen reduction in (b) region (i) and region (iii).ECR應用實例應用實例水對電極材料的影響水對電極材料的影響XPS d

14、epth profiling analysis on LSCF cathode after long-term exposure(150h) in wet atmosphere.ECR應用實例應用實例水對電極材料的影響水對電極材料的影響ECR應用實例應用實例水對電極材料的影響水對電極材料的影響ECR應用實例應用實例元素中毒對電極的影響元素中毒對電極的影響Ling Zhao, Tatsumi Ishihara and San Ping Jiang, Journal of The Electrochemical Society, 160 (6) F682-F686 (2013)SEM microg

15、raphs of LSCF surface after heat-treatment for 48 h in the absence of E-glass at (a) 700 C, (c) 750 C, (e) 800 C and in the presence of E-glass at (b) 700 C, (d) 750 C, (f) 800 C.(g) Without heat treatmentECR應用實例應用實例元素中毒對電極的影響元素中毒對電極的影響SIMS depth profiles analysis of LSCF surface after heat-treatmen

16、t in the presence of E-glass for 48 h at (a) 700 C, (b) 750 C and (c) 800 C.ECR應用實例應用實例元素中毒對電極的影響元素中毒對電極的影響Experimental data of electrical conductivity relaxation as a function of time on LSCF in the presence of E-glass at 700,750,800 C測試測試-降溫降溫升溫（升溫（5/min）-測試測試ECR應用實例應用實例元素中毒對電極的影響元素中毒對電極的影響Plots of fitted surface exchange coefficients as a function of time in the absence and presence of E-glassECR應用實例應用實例元素中毒對電極的影響元素中毒對電極的影響總結總結ECR測試方法相比于其他測試方法操作更加簡便，所需設備更加簡單，耗時更短。測試方法