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:nopowerdropfor750oC@0.5A/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