電導(dǎo)弛豫法研究SOFC陰極材料

利用電導(dǎo)弛豫方法研究燃料電池陰極材料小組成員：謝云，史鼐，孫樂(lè)，陳明龍，黃晉，馬致遠(yuǎn)。報(bào)告人：史鼐Outline:SOFC背景介紹應(yīng)用舉例電導(dǎo)弛豫方法及影響因素總結(jié)O-SOFC示意圖P-SOFC示意圖SOFC基本原理燃料電池陰極反應(yīng)La0.6Sr0.4Co0.2Fe0.8O3-d表面氧交換k(cms-1)內(nèi)部氧擴(kuò)散D(cm2s-1)傳統(tǒng)測(cè)量方法：兩端子法（伏安法）四端子法測(cè)電導(dǎo)率接觸點(diǎn)和導(dǎo)線電阻不可忽略，尤其對(duì)電阻較小的材料，測(cè)量不準(zhǔn)確四端子法測(cè)量電導(dǎo)率四端子法測(cè)電阻示意圖Fick第二定律：ECR理論基礎(chǔ)其中l(wèi)為最小心樣品尺寸的一半定義復(fù)合函數(shù)邊界條件為：通過(guò)分離變量，可得：（1）（2）邊界條件：討論λ取值只有當(dāng)λ>0時(shí)滿(mǎn)足，解得代入邊界條件可得

令有最后代入函數(shù)并化簡(jiǎn)得。。。。。。。（1）即時(shí)，若令，則，可得

（1）即

時(shí)，若令，則，可得

根據(jù)質(zhì)量守恒及缺陷平衡方程可得則

此時(shí)材料電導(dǎo)率僅與時(shí)間t有關(guān)，與樣品內(nèi)位置x無(wú)關(guān)，可認(rèn)為樣品電導(dǎo)率均勻分布表面擴(kuò)散控制（2）即時(shí)，

（3）時(shí)，

體擴(kuò)散控制雙重控制理論基礎(chǔ)推廣到三維，歸一化電導(dǎo)弛豫曲線：其中：弛豫曲線與氧分壓關(guān)系理論基礎(chǔ)擬合求解方法一：1,確定D,k初步范圍2,求解誤差分布3,篩選結(jié)果(控制步驟）方法二：1,選定初始D,k值2,擬合優(yōu)化D,k結(jié)果3,變換初始值多次擬合SFM樣品弛豫曲線的擬合誤差與D、k值的關(guān)系Relativeasymptoticerrorsontheestimated^kand^D獲得D,k值的影響因素——擬合影響FrancescoCiucci,SolidStateIonics239(2013)28–40獲得D,k值的影響因素——?dú)怏w切換速度時(shí)間常數(shù)

M.W.denOtter,H.J.M.Bouwmeester,B.A.Boukamp,H.Verweij,JournalofTheElectrochemicalSociety,148(2001)J1-J6獲得D,k值的影響因素——氧分壓梯度對(duì)于LSCF

S.Wang,A.Verma,Y.L.Yang,A.J.Jacobson),BenAbeles,SolidStateIonics140(2001)125–133獲得D,k值的影響因素——表面微觀結(jié)構(gòu)晶粒大小晶界密度（長(zhǎng)度）原料分體性質(zhì)燒結(jié)溫度，時(shí)間制備過(guò)程YunlongWang,YaoWang,ChangrongXia,JournalofTheElectrochemicalSociety,159(9)F570-F576(2012)

ECR應(yīng)用舉例——Sr3YCo4O10.5電極材料Preparationmethod:SSR(SrCO3,Co3O4,Y2O3)Sinteringtemperature:900℃~1200℃Samplesinteringtemperature:1180℃/4hDensity>95%Size:t=1.43mm,w=1.09mm,l=19.72mmElectricalconductivityofSr3YCo4O10.5inairMax=550S/cmOxygenvacanciesformationThermalactivationArelativeelectricalconductivityvs.timeprofileobtainedduringanECRexperimentat850℃withanoxygenpartialpressureswitchfrom10%to75%andthecorrespondingfitComparingofprofilesofrelativeconductivity.g(t).ofSr3YCo4O10.5vs.timeobtainedduringECRexperimentsatdifferenttemperaturesandforswitchesofoxygenpartialpressurefrom10%to75%ECR應(yīng)用舉例——Sr3YCo4O10.5電極材料K和初始氧分壓無(wú)關(guān)，和平衡氧分壓有關(guān)D和氧分壓無(wú)關(guān)，只和溫度有關(guān)ArrheniusplotofthechemicaloxygendiffusionandchemicalsurfaceexchangecoefficientsobtainedforSr3YCo4O10.5byECRexperimentsECR應(yīng)用舉例——Sr3YCo4O10.5電極材料DependenceofchemicalsurfaceexchangerateforSr3YCo4O10.5onthefinaloxygenpartialpressureduringECRswitchesOxygencontentinSr3YCo4O10.5dependenceonoxygenpartialpressureinthesurrendingsandtemperaturedeterminedbyTGA

溫度升高，氧濃度減少ECR應(yīng)用舉例——Sr3YCo4O10.5電極材料熱力學(xué)因子自擴(kuò)散系數(shù)Comparisonofoxygenself-diffusioncoefficientsinSr3YCo4O10.5determinedbyECR(thiswork),IEDP/SIMSandmoleculardynamicsECR應(yīng)用舉例——Sr3YCo4O10.5電極材料ECR應(yīng)用實(shí)例——水對(duì)電極材料的影響Schematicrepresentationofcathodereactioninprotonicceramicfuelcells(PCFCs)Ho-IlJi,Sung-MinChoi,KyungJoongYoon,Ji-WonSon,Byung-KookKim,Hae-WeonLee,Jong-HoLee,SolidStateIonics249–250(2013)112–116Variationsinconductivityafterthegaswaschangedfromdryairtowetairat700℃.Conductivityrelaxationcurveduringacycleofchangesinthegasfromwettodryairandthenfromdrytowetairin(b)region(i)and?region(ii).abcECR應(yīng)用實(shí)例——水對(duì)電極材料的影響Conductivitychangeafterthegaswaschangedfromdryairtowetair.Conductivityrelaxationsuponoxygenreductionin(b)region(i)and?region(iii).ECR應(yīng)用實(shí)例——水對(duì)電極材料的影響XPSdepthprofilinganalysisonLSCFcathodeafterlong-termexposure(150h)inwetatmosphere.ECR應(yīng)用實(shí)例——水對(duì)電極材料的影響

ECR應(yīng)用實(shí)例——水對(duì)電極材料的影響ECR應(yīng)用實(shí)例——元素中毒對(duì)電極的影響LingZhao,TatsumiIshiharaandSanPingJiang,JournalofTheElectrochemicalSociety,160(6)F682-F686(2013)

SEMmicrographsofLSCFsurfaceafterheat-treatmentfor48hintheabsenceofE-glassat700?C,(c)750?C,(e)800?CandinthepresenceofE-glassat(b)700?C,(d)750?C,(f)800?C.(g)WithoutheattreatmentECR應(yīng)用實(shí)例——元素中毒對(duì)電極的影響SIMSdepthprofilesanalysisofLSCFsurfaceafterheat-treatmentinthepresenceofE-glassfor48hat(a)700?C,(b)750?Cand(c)800?C.ECR應(yīng)用實(shí)例——元素中毒對(duì)電極的影響ExperimentaldataofelectricalconductivityrelaxationasafunctionoftimeonLSCFinthepresenceofE-glassat700,750,800?C測(cè)試--降溫—升溫（5℃/min）--測(cè)試ECR應(yīng)用實(shí)例——元素中毒對(duì)電極的影響Plotsoffittedsurfaceexchangecoefficientsasafunctionoft