Cobalt-FreeBa0.95La0.05FeO3−δThinFilmsasCathodesforIntermediate-TemperatureSolid
OxideFuelCells
1
FrancescoCiucci,C.Chen,Z.M.Baiyee,D.ChenTheHongKongUniversityofScienceandTechnologyDept.ofMechanicalandAerospaceEngineeringDept.ofChemicalandBiomolecularEngineering
Z.ShaoChemicalEngineering,CurDnUniversity,Australia
ChemicalEngineering,NanjingTech,China
Outline
• IntroducDon• WhyLa-dopedBaFeO3(BLF)?• LaQcesimulaDons(howmuchLa?)• PLD-depositedthinfilms:hightempORRperformance
• MolecularDynamicsinsightintoOtransport• FirstprincipleanalysisofvacancyformaDonenergies
• Conclusion
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StateofTheArtCathodes
1. Ba0.5Sr0.5Co0.8Fe0.2O3-δ(BSCF)–CubicperovskitebutstructuraltransformaDonfromthehigh-acDvitycubicperovskitephase(lowpolarizaDonlosses)toalow-acDvity(highpolarizaDon)hexagonalphase[1].
2. Ba0.95La0.05FeO3-δ(BLF)–AcDvitycomparabletoBSCF[2].
[1]Z.Shao&S.M.HaileNature431,170-173(2004)[2]F.F.Dongetal.J.Mater.Chem.22,15071-15079(2012)
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WhyBLF?• AreaSpecificResistance(ASR)~0.037Ωcm2at700°C
• Ni+YSZanode/YSZelectrolyte/SDCinterlayer/BLFcathode– Peakpowerdensity:1.35Wcm-2@750°C– Stability:[email protected]/cm2for400h
– NoASRdegradaDonforsymmetriccells1200h@700°C
4 F.Dongetal.J.Mater.Chem.22,15071-15079(2012) SDC=Sm0.15Ce0.85O2-δYSZ=8%Y2O3stabilizedZrO2
WhyBLF?(cont’d)• HighperformanceasoxygenpermeaDonmembrane[1,2]• MixedConductor• AcDvitycomparabletoCo-basedmaterialswithoutthe
disadvantages– HighpriceofCo– Largevolumeexpansion
• BeperperformanceincomparisontootherFe-basedperovskites,i.e.,La1−xSrxFeO3−δ[3],Ba1−xSrxZn1−yFeyO3−δ[4],andBi1−xSrxFeO3−δ[5]
• InteresDngly,BFOisdifficulttomake.TradiDonalmethods(sol-gelorsolidstatesynthesis)don’tgivehighacDvitycubicphase.
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[1]Shimanoeetal.Adv.Mater.22,21,2367–2370(2010)[2]Shimanoeetal.ACSAppl.Mater.Interfaces,2,2849–2853(2010)
[3]Stevenson,J.PowerSources,113,1–10(2003)[4]J.Caroetal.Adv.Mater.,17,1785–1788(2005)[5]Z.Shaoetal.,J.Mater.Chem.,20,9619–9622(2010)
Ladopantstabilizesthecubicstructure
• BysubsDtuDngLaintotheBasiteofBaFeO3-δ,itwasobservedthatthematerialisstabilizedintoasinglecubicperovskitephase.
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Shaoetal.,J.Mater.Chem.,20,9619–9622(2010)
tBa
1�x
Lax
FeO3
G < tBaFeO3
GtBaFeO3G =
rBa + rOp2(rFe + rO)
> 1.0
• However,inoxygenpermeaDonmembranesincreasingLasubsDtuDonresultsinadecreaseoxygenpermeaDonflux
LaQceCalculaDonPrisDneBaFeO2.5
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−108.67eV−108.70eVLaQceEnergy
Introducing decreasesthelaQceenergymorestronglyonthecubicthanthemonoclinicphase
C.Chen,F.Ciuccietal.J.Mater.Chem.A,2,14154-14163(2014)
La•Ba
MD(640unitcellsand2896ions)tostudyimpactofLaonoxygendiffusioncoefficientinNVTensemble.
La
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DandEaconsistentwithpublishedexperimentsF.F.Dongetal.J.Mater.Chem.22,15071-15079(2012)
ImpedanceofPLD-depositedsymmetriccells
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BLF
BLF
YSZ
DepositedwithPLD
GrownwithPLD
SingleCrystalThinSamarium-doped(15%)CeO2interlayer(depositedwithPLD)
Rp
10
Chen,Ciuccietal.JournalofPowerSources250,188-195(2014)Chen,Ciuccietal.J.Mater.Chem.A2(34),14154-14163(2014)
Allthinfilms<complicaDonfromgeometry
oriented
Beper!
Thethickness~50-100nm(TEM&XRR).
11Chen,Ciuccietal.J.Mater.Chem.A2(34),14154-14163
Thefilmrotates45degreesw.r.t.thesubstrateandtheinterlayer.
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p2 aBLF ⇡ aSDC
p2 4.013 A ⇡ 5.416 A
Fromthereciprocalspacemap,weobtainedthatthefilmisrelaxedexcludingthatstraineffectsinfluencetheelectrochemicalproperDes.
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XPS=>composiDonmatchesthePLDtarget.FromXPSdepthprofile,FedepleDon/BaenrichmentoccursattheBLFsurface.
TheFe2pelectronisfipedby2valencestates(Fe3+andFe4+),whichgivestheaveragevalenceof3.13
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Rp / p�0.5O2
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Eainagreementw/F.Dongetal.J.Mater.Chem.22,15071-15079(2012)
DataDrivenMolecularDynamics
16C.Chen,D.Chen,andF.CiucciPhys.Chem.Chem.Phys.,2015,17,7831-7837
Dataminingthetrajectories~40Gb
WeclustertheoxygenlocaDonsohastodeterminelocalinformaDonsuchashoppingprobabiliXes,rates,anddwellXmes
17Ba0.5La0.5FeO3-δ
#ofoxygenpe
rsite
#ofoxygenpe
rsite
NatureofDiffusioninBa0.5La0.5FeO3-δ1573K
C.Chen,Z.M.Baiyee,andF.CiucciPhys.Chem.Chem.Phys.DOI:10.1039/C5CP03973H
NatureofDiffusioninBa0.5La0.5FeO3-δ(cont’d)
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Easytoescapecagec5(LaLaLaLa)
Hardtoescapecagec1(BaBaBaBa)
NatureofDiffusioninBa0.5La0.5FeO3-δ(cont’d)
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bopleneck(BaBaFe) bopleneck(LaLaFe) bopleneck(BaLaFe)
Normalizedjumpratethroughbopleneck=#jumpsoverabopleneckin1psdividedbythetotalnumberofboplenecks
NatureofDiffusioninBa0.5La0.5FeO3-δ(cont’d)
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Rateofjum
psth
roughbo
plene
ck
0.814Å 0.898Å 0.976Å
NatureofDiffusioninBa0.5La0.5FeO3-δ(cont’d)
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cumulaD
vedistrib
uDon
funcDo
n
OxygendwellDme(ps)
LarichBarich
NatureofDiffusioninBa0.5La0.5FeO3-δ(cont’d)
22
averagedw
ellDme
MD(640unitcellsand2896ions)tostudyimpactofLaonoxygendiffusioncoefficientinNVTensemble.
La
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DandEaconsistentwithpublishedexperimentsF.F.Dongetal.J.Mater.Chem.22,15071-15079(2012)
NatureofDiffusioninBLF(cont’d)
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prob
abilityofo
xygenjumpover1ps
ProbabilityofhoppingandthediffusioncoefficientdecreasewithLaasaresultofthistradeoff
LalowersthemigraDonbarrierbutalsodecreasesvacancyconcentraDon.
Ba1-xLaxFeO3−δ
Ladopantdecreasestheperformance
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MigraDonandvacancyformaDonenergies(firstprinciples)
VASPsimulaDons:C.Chen,D.Chen,andF.CiucciPhys.Chem.Chem.Phys.,2015,17,7831-7837
DFTcalculaDonssupportsmallerbarrierneartheLasite.
Ladopantstabilizesthecubicstructure,butdecreasestheperformance
OxygenvacancyformaDonenergy• BaFeO3:Evac=0.90eV• Ba0.875La0.125FeO3:Evac=1.14eV• Ba0.875La0.125FeO2.875:Evac=1.36eV• Ba0.875La0.125FeO2.75:Evac=1.75eVDonordoping(La3+)hindersthepresenceofotherdonors(vacancies).
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VASPsimulaDons:Z.M.Baiyee,C.Chen,andF.Ciucci,PhysicalChemistryChemicalPhysics,2015DOI:10.1039/C5CP02694F
HighO2pbandcenter O2pband(DOS)centerisindicaDveofcatalyDcacDvity.TheclosertoEFthecenteris,thebeper.
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Ba0.875La0.125FeO3-1.75eV Ba0.75La0.25FeO3-1.99eV BaFeO3-1.62eV
Ref:-1.54eVforBa0.5Sr0.5Co0.8Fe0.2O3,-1.85eVforPrBaCo2O6Morganetal.EnergyEnviron.Sci.4.10(2011):3966-3970.Shao-hornetal.NaturecommunicaDons4(2013)
BLFaferromagneDc(FM)conductor
LaQceenergy(eV)performulaunit(f.u.)fordifferentmagneDcstates.
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FM AAFM CAFM GAFM
BaFeO3 -31.93 -31.85 -31.78 -31.66
Ba0.875La0.125FeO3 -32.79 -32.72 -32.67 -32.57
Ba0.75La0.25FeO3 -33.60 -33.53 -33.49 -33.40
Conclusions• BLF(Co-free&highacDvity)• Lastabilizesstructure(thesmallerLasubsDtuDonthebeper)
• cubicBFOhashighacDvity[1]moreLahasadverseeffectonperformance(Ladonor)
• BLFisalsoanexcellentmaterialforOERatlowtemperature[2]
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[1]F.F.Dongetal.ACSAppl.Mater.Interfaces,6,14,11180–11189(2014)[2]H.Zhaoetal.90,122–129Carbon(2015)
Conclusions(cont’d)• WealsostudiedtheeffectofAandBsitesubsDtuDonbothexperimentallyandtheoreDcally[1,2]
• CO2toleranceisenhancedbyeliminaDngalkaline-earthelementsfromA-site[3]butitwasrecentlyreportedthatBa0.95La0.05Fe0.85Zr0.15O3-δisCO2stableasoxygentransportaDonmembrane[4]
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[1]Z.M.Baiyeeetal.PCCP17(2015)23511-23520[2]J.Wangetal.JournalofPowerSources297(2015)511-518[3]YChen,MLiu,FCiucci,ZShao-AdvancesinCathodeMaterialsforSolidOxideFuelCells:ComplexOxideswithoutAlkalineEarthMetalElementsAdvancedEnergyMaterials[4]Chengetal.JournalofMembraneScience492(2015)220–229
Thankyou!
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