Cobalt-Free Ba0.95La0.05FeO Cathodes for Intermediate ... · Cathodes for Intermediate-Temperature...
31
Cobalt-Free Ba 0.95 La 0.05 FeO 3−δ Thin Films as Cathodes for Intermediate-Temperature Solid Oxide Fuel Cells 1 Francesco Ciucci, C. Chen, Z.M. Baiyee, D. Chen The Hong Kong University of Science and Technology Dept. of Mechanical and Aerospace Engineering Dept. of Chemical and Biomolecular Engineering Z. Shao Chemical Engineering, CurDn University, Australia Chemical Engineering, Nanjing Tech, China
Transcript of Cobalt-Free Ba0.95La0.05FeO Cathodes for Intermediate ... · Cathodes for Intermediate-Temperature...
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
2
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)
3
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.
5
[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.
6
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
7
−108.67eV−108.70eVLaQceEnergy
Introducing decreasesthelaQceenergymorestronglyonthecubicthanthemonoclinicphase
C.Chen,F.Ciuccietal.J.Mater.Chem.A,2,14154-14163(2014)
La•Ba
MD(640unitcellsand2896ions)tostudyimpactofLaonoxygendiffusioncoefficientinNVTensemble.
La
8
DandEaconsistentwithpublishedexperimentsF.F.Dongetal.J.Mater.Chem.22,15071-15079(2012)
ImpedanceofPLD-depositedsymmetriccells
9
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.
12
p2 aBLF ⇡ aSDC
p2 4.013 A ⇡ 5.416 A
Fromthereciprocalspacemap,weobtainedthatthefilmisrelaxedexcludingthatstraineffectsinfluencetheelectrochemicalproperDes.
13
XPS=>composiDonmatchesthePLDtarget.FromXPSdepthprofile,FedepleDon/BaenrichmentoccursattheBLFsurface.
TheFe2pelectronisfipedby2valencestates(Fe3+andFe4+),whichgivestheaveragevalenceof3.13
14
Rp / p�0.5O2
15
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)
18
Easytoescapecagec5(LaLaLaLa)
Hardtoescapecagec1(BaBaBaBa)
NatureofDiffusioninBa0.5La0.5FeO3-δ(cont’d)
19
bopleneck(BaBaFe) bopleneck(LaLaFe) bopleneck(BaLaFe)
Normalizedjumpratethroughbopleneck=#jumpsoverabopleneckin1psdividedbythetotalnumberofboplenecks
NatureofDiffusioninBa0.5La0.5FeO3-δ(cont’d)
20
Rateofjum
psth
roughbo
plene
ck
0.814Å 0.898Å 0.976Å
NatureofDiffusioninBa0.5La0.5FeO3-δ(cont’d)
21
cumulaD
vedistrib
uDon
funcDo
n
OxygendwellDme(ps)
LarichBarich
NatureofDiffusioninBa0.5La0.5FeO3-δ(cont’d)
22
averagedw
ellDme
MD(640unitcellsand2896ions)tostudyimpactofLaonoxygendiffusioncoefficientinNVTensemble.
La
23
DandEaconsistentwithpublishedexperimentsF.F.Dongetal.J.Mater.Chem.22,15071-15079(2012)
NatureofDiffusioninBLF(cont’d)
24
prob
abilityofo
xygenjumpover1ps
ProbabilityofhoppingandthediffusioncoefficientdecreasewithLaasaresultofthistradeoff
LalowersthemigraDonbarrierbutalsodecreasesvacancyconcentraDon.
Ba1-xLaxFeO3−δ
Ladopantdecreasestheperformance
25
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).
26
VASPsimulaDons:Z.M.Baiyee,C.Chen,andF.Ciucci,PhysicalChemistryChemicalPhysics,2015DOI:10.1039/C5CP02694F
HighO2pbandcenter O2pband(DOS)centerisindicaDveofcatalyDcacDvity.TheclosertoEFthecenteris,thebeper.
27
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.
28
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]
29
[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]
30
[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!
31
EarlyCareerSchemeGrant
