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8/19/2019 perovskite ctlyst and its uses......
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1
11Materials Science&Technology
PerovskitePerovskite--typetype photocatalystsphotocatalysts
AnkeAnke Weidenkaff Weidenkaff
www.empa.ch/awww.empa.ch/abt.131bt.131
TEPTEP--CHCH girlsgirls dayday DESYDESY SINQSINQ
PhDPhD stud. daystud. day
22Materials Science&Technology
LaboratoryLaboratory forfor Solid StateSolid State ChemistryChemistry andand CatalysisCatalysis
Weidenkaff, A.Weidenkaff, A.
AbteilungsleiterinAbteilungsleiterin
Weidenkaff, A.Weidenkaff, A.
Solid StateSolid State ChemistryChemistry
--Aguirre, M.Aguirre, M.
--Trottmann, M.Trottmann, M.
-Robert, R.
--LogvinovichLogvinovich, D., D.
--ShkabkoShkabko, A., A.
--BocherBocher, L., L.
--Tomes, P.Tomes, P.
--SchSchääuble, N.uble, N.
--HHäämmerlimmerli, A., A.
--ToggweilerToggweiler, S., S.
Hanselmann, K.Hanselmann, K.
SekretariatSekretariat
Ferri Ferri , D. , D.
HeterogeneousHeterogeneous CatalysisCatalysis
--NNNN
--HugHug
, P., P.
--KorsakKorsak, O., O.
--EysslerEyssler, A., A.
--AglaeAglae, A., A.
N.N.N.N.
Solid State AnalysisSolid State Analysis
--LienemannLienemann, P., P.
--GfellerGfeller
, U., U.
--BukowieckiBukowiecki, N., N.
•• SRSR--XRFXRF analysisanalysis
ofof tracetrace elementselements
in ambientin ambient airair
•• NovelNovel exhaustexhaust gasgas
catalystscatalysts
•• InIn--situsitu spectroscopyspectroscopy•• ThermoelectricThermoelectric
materialsmaterials
•• PerovskitePerovskite--typetype
oxynitridesoxynitrides
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2
33Materials Science&Technology
Focal points of the laboratoryFocal points of the laboratory
1.1. Solid State Materials ChemistrySolid State Materials Chemistry
Synthesis and characterization of tailorSynthesis and characterization of tailor--mademade perovskiteperovskite--type functional materialstype functional materials
with improved properties for potential applications in energy cowith improved properties for potential applications in energy conversionnversion
technologies, such astechnologies, such as thermoelectric converters, solarthermoelectric converters, solar photocatalyticphotocatalytic cells, andcells, and
exhaust gas treatmentexhaust gas treatment..
2.2. Heterogeneous CatalysisHeterogeneous Catalysis
Improvement of present catalytic materials to reduce pollutants.Improvement of present catalytic materials to reduce pollutants. Finding newFinding new
methods for the clarification of the nature, structure, sorptivemethods for the clarification of the nature, structure, sorptive and reactiveand reactive
features of catalytic sites at the surface of catalysts and thefeatures of catalytic sites at the surface of catalysts and the behavior of thebehavior of the
catalyst components under reaction conditionscatalyst components under reaction conditions..
3.3. Inorganic Solid State AnalysisInorganic Solid State Analysis
MacroMacro--, micro, micro-- andand nanoscopicnanoscopic analysis of the chemical composition and structureanalysis of the chemical composition and structure
of solids, such as e.g. novel crystalline phases, functional matof solids, such as e.g. novel crystalline phases, functional materials, and particleserials, and particles
from synthetic and natural sources. The elemental and structuralfrom synthetic and natural sources. The elemental and structural analysis isanalysis is
performed by usingperformed by using XrayXray (synchrotron), electron(synchrotron), electron-- and neutron probe techniquesand neutron probe techniques,,
i.e. XRD, ND, XRF, XPS, TEM and XAS.i.e. XRD, ND, XRF, XPS, TEM and XAS.
44Materials Science&Technology
FKCh@empaFKCh@empa:: ““tailoringtailoring”” of functional materialsof functional materials
SStteepp 11:: DDeef f iinnii tt iioonn oof f RReeqquuiir r eemmeennttss FFuunnccttiioonn:: ee..gg.. ttr r aannssppoor r tt ppr r ooppeer r ttiieess,, r r eeaaccttiivviittyy,, ssttaabbiilliittyy ……
SStteepp 22:: CChhooiiccee oof f MMaatteer r iiaallss
ee..gg.. ppeer r oovvsskkiitteess A AMMXX33
SStteepp 44::
CChhaar r aacctteer r iissaatt iioonn
•• SSttr r uuccttuur r ee aanndd ccoommppoossiittiioonn •• DDyynnaammiicc ppr r oocceesssseess:: ttr r aannssppoor r tt,, r r eeaaccttiivviittyy
SStteepp 33:: TTaaii lloor r iinngg ssyynntthheessiiss mmeetthhooddss :: ee..gg.. ““cchhiimmiiee ddoouuccee““ aanndd aaeer r oossooll ppr r oocceesssseess
tteesstt tthheeoorryy,,
eeccoonnoommyy,, eennvviirroonnmmeenntt
„ „structurestructure--compositioncomposition--propertyproperty--relationrelation “ “
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55Materials Science&Technology
SynthesisSynthesis methodsmethods
•• SoftSoft chemistrychemistry,, microemulsionmicroemulsion,, ……
•• SolSol--gelgel
•• UltrasonicUltrasonic sprayspray combustioncombustion
•• MicrowaveMicrowave inducedinduced plasmaplasma
•• PLD at PSIPLD at PSI20 nm
101
01-1
[-111]
110
USCUSC
rotatingrotating cavitycavity
MIPMIPMesoporousMesoporous (La,Sr)TiO(La,Sr)TiO
33
66Materials Science&Technology
CharacterisationCharacterisation ofof structurestructure,, compositioncomposition,, propertiesproperties
•• TGATGA--MSMS Thermogravimetrie mit gekoppelter Massenspektroskopie UntersuchuThermogravimetrie mit gekoppelter Massenspektroskopie Untersuchung der thermischenng der thermischen
Eigenschaften (ReaktivitEigenschaften (Reaktivitäät und Stabilitt und Stabilitäät)t) von Materialien wie z.B.von Materialien wie z.B. GasGas--Feststoff Feststoff --ReaktionenReaktionen,,
Phasenumwandlungen, Reaktionsuntersuchungen mit der Pulse TAPhasenumwandlungen, Reaktionsuntersuchungen mit der Pulse TA
•• DSCDSC DifferentialDifferential ScanningScanning CalorimeterCalorimeter Dynamisches WDynamisches Wäärmestrom Kalorimeterrmestrom Kalorimeter WWäärmekapazitrmekapazitäätsts--
MessungenMessungen ((CpCp) Messung von) Messung von UmwandlungswUmwandlungswäärmenrmen ((ΔΔH) in verschiedenen AtmosphH) in verschiedenen Atmosphäären,ren,
temperaturabhtemperaturabhäängig bis 1400ngig bis 1400 °°CC
•• XRDXRD PhasenanalysePhasenanalyse mitmit RRööntgendiffraktionsmethoden/Rietveldntgendiffraktionsmethoden/Rietveld
•• NDND PhasenanalysePhasenanalyse mitmit Neutronendiffraktionsmethoden/RietveldNeutronendiffraktionsmethoden/Rietveld
•• XRFXRF RRööntgenfluoreszenzspektroskopie, Ermittlung derntgenfluoreszenzspektroskopie, Ermittlung der ZusammensetzungZusammensetzung diverser Proben.diverser Proben.
•• XASXAS RRööntgenabsorptionsspektroskopie,ntgenabsorptionsspektroskopie,EXAFS, XANESEXAFS, XANES
••
RamanRaman
--MikroskopieMikroskopie
, In, In
--situsitu
RamanRaman
--MikroskopieMikroskopie
zurzur
PhasenanalysePhasenanalyse
,,
KristallinitKristallinit
äätt, Bestimmung von, Bestimmung von
OberflOberfläächenspezieschenspezies..
•• InfrarotInfrarot-- SpektroskopieSpektroskopie,, operandooperando und inund in--situ Untersuchungen chemischer Reaktionen.situ Untersuchungen chemischer Reaktionen.
•• REMREM –– EDXEDX Rasterelektronenmikroskopie EnergyRasterelektronenmikroskopie Energy DispersiveDispersive XrayXray AnalysisAnalysis
•• TEMTEM Transmissionselektronenmikroskopie, HochauflTransmissionselektronenmikroskopie, Hochauflöösende Transmissionselektronenmikroskopie zursende Transmissionselektronenmikroskopie zur
Untersuchung desUntersuchung des atomaren Aufbaus undatomaren Aufbaus und --OrdnungOrdnung von Festkvon Festköörpern,rpern, ElektronendiffraktionElektronendiffraktion zurzur
PhasenanalysePhasenanalyse
•• BETBET BrunnauerBrunnauer EmmetEmmet Teller MethodeTeller Methode GassorptionsGassorptions--MessungenMessungen zur Bestimmung derzur Bestimmung der spezifischenspezifischen
OberflOberfläächeche (BET(BET--OberflOberflääche) in m2/g, TPR (che) in m2/g, TPR (TemperatureTemperature ProgrammedProgrammed ReductionReduction) TPD () TPD (TemperatureTemperature
ProgrammedProgrammed Desorption)TPODesorption)TPO ((TemperatureTemperature ProgrammedProgrammed Oxidation)ChemisorptionOxidation)Chemisorption
•• LFALFA Messungen derMessungen der WWäärmeleitf rmeleitf äähigkeithigkeit von Werkstoffen mit dervon Werkstoffen mit der LaserLaser--flashflash Methode bis 1100Methode bis 1100°°CC
•• HochtemperaturtransportmessungenHochtemperaturtransportmessungen, Bestimmung der elektrischen Leitf , Bestimmung der elektrischen Leitf äähigkeit undhigkeit und
thermoelektrischen Eigenschaftenthermoelektrischen Eigenschaften von Materialien (elektrischer Widerstand,von Materialien (elektrischer Widerstand, SeebeckSeebeck--KoeffizientKoeffizient,, FigureFigure
ofof meritmerit) bis 1100) bis 1100°°C.C.
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77Materials Science&Technology
DevelopmentDevelopment ofof nonnon--conventionalconventional thermoelectricsthermoelectrics
p p--type: GdCotype: GdCo0.950.95NiNi0.050.05OO33
nn--type: CaMntype: CaMn0.980.98NbNb0.020.02OO33
NewNew temperaturetemperature stablestable nanostructurednanostructured
thermoelectricthermoelectric materialsmaterials
BestBest nn--typetype thermoelectricthermoelectric perovskitesperovskites
CaMnCaMn11--xxNbNbxxOO33±δ±δ
ReductionReduction of thermalof thermal conductivityconductivity
byby >> factorfactor 33
First PerovskiteFirst Perovskite ThermoelectricThermoelectric OxideOxide
Module (TOM)Module (TOM)
Test stand: TTest stand: T--,V,V--Measurement withMeasurement with
LABVIEWLABVIEW--logging unitlogging unit
3D3D--Simulation: direct coupled thermalSimulation: direct coupled thermal ––
electrical simulation finite elementselectrical simulation finite elements
method (coop A.method (coop A. BitschiBitschi, ETHZ), ETHZ)
88Materials Science&Technology
AnionicAnionic substitutionssubstitutions: Oxynitride Perovskites: Oxynitride Perovskites
LaNbON2
orthorhombicNb-(O,N)-Nb = 160°
Pnma
New compounds with interesting properties:New compounds with interesting properties:
highly conductive material: SrMoOhighly conductive material: SrMoO22NN
HeterostructuresHeterostructures with different Nwith different N--content showcontent show
giant Seebeck, resistivity switching andgiant Seebeck, resistivity switching and
superconductivitysuperconductivity
potential new water splitting catalyst withpotential new water splitting catalyst with
bandgapbandgap 1.71.7 eVeV : LaNbON: LaNbON22
-5 -4 -3 -2 -1 0 1 2 3 4 5
-0.05
-0.04
-0.03
-0.02
-0.01
0.00
0.01
0.02
0.03
0.04
0.05
C u r r e n t , A
Voltage, V
300 K
160 K
9 K
-3 -2 -1 0 1 2 3
-1
0
1
-8 -6 -4 -2 0 2 4 6 8
-0.5
0.0
0.5
-2
-1
0
1
2
D O S
/ ( e V , c e l l )
Energy (eV)
total
Motot
Otot
Moeg
Mot2g
D O S / ( e V , a t o m )
DOS_srmonU20
total
Motot
Otot
Srtot D O S
/ ( e V , c e l l )
E. Selli, et al Chem. Commun., 2007, 5022
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99Materials Science&Technology
Oxynitride Perovskites challengesOxynitride Perovskites challenges
HH
LiLi
NaNa
BeBe
KK
MgMg
ScScCaCa CuCu
SrSr
GaGaZnZn
RaRa
BaBa
FrFr
CsCs
RbRb
NiNiCoCoFeFeMnMnCrCrVVTiTi
YY AgAg CdCdPdPdRhRhRuRuTcTcMoMoNbNbZrZr
LnLn AuAu HgHgPtPtIrIrOsOsReReWWTaTaHf Hf
HeHe
BB
AlAl
InIn
TlTl
CC NN OO FF NeNe
SiSi
GeGe
SnSn
RnRnPbPb BiBi PoPo AtAt
PP SS ClCl ArAr
AsAs SeSe BrBr KrKr
SbSb TeTe JJ XeXe
AcAc
A2B(O,N)4 A4B3(O,N)10AB(O,N)3 A3B2(O,N)7
•• Structural investigations onStructural investigations on
perovskiteperovskite--type oxynitrides are raretype oxynitrides are rare
•• Only polycrystalline samples areOnly polycrystalline samples are
describeddescribed
•• Physical properties are inadequatelyPhysical properties are inadequately
characterisedcharacterised until nowuntil now
1010Materials Science&Technology
UVUV--Vis diffusive reflectance spectroscopy of (La,Ca)Ti(O,N)Vis diffusive reflectance spectroscopy of (La,Ca)Ti(O,N)33
0.0 0.2 0.4 0.6 0.8 1.0
2.4
2.8
3.2
3.6 blue
light green
green
dark greenred-violett
B
a n d
g a p
[ e V ]
Ca content
10 20 30 40 50 60 70 80
I n t e n s i t y
2Θ [o]
XRDXRD (La,Ca)Ti(O,N)(La,Ca)Ti(O,N)33
E
M (nd)
O (2p)
N (2p)
M (nd)
O (2p)
E
•• BB--N more covalent thanN more covalent than BB--OO
•• band gap reducedband gap reduced
pigmentspigments
photocatalystsphotocatalysts
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1111Materials Science&Technology
BaTaOBaTaO22NN
CubicCubicTaTa--OO--Ta = 180Ta = 180°°Gap 1.8 eVGap 1.8 eV
CaTaOCaTaO22NN
OrthorhombicOrthorhombicTaTa--OO--Ta = 153Ta = 153°°
Gap 2.4 eVGap 2.4 eV
SrTaOSrTaO22NN
TetragonalTetragonalTaTa--OO--Ta = 170Ta = 170°°
Gap 2.1 eVGap 2.1 eV
E
O 2p
N 2p
ΔE1
E
O 2p
N 2p
E
O 2p
N 2p
ΔE2 ΔE3
M nd M nd M nd
E
O 2p
N 2p
ΔE2
M nd
E
O 2p
N 2p
ΔE1
M nd
E
O 2p
N 2p
ΔE3
M nd
SmallerSmaller MM--OO--MM anglesangles leadlead to anto an
decreasedecrease ofof thethe d d --bandband widthwidth and anand an
increaseincrease ofof thethe bandband gapgap..
DecreasingDecreasing EN ofEN of thethe transitiontransition--metalmetal
leadsleads to anto an increaseincrease ofof thethe bandband gapgap..
••O/N content control by crossO/N content control by cross--substitutionsubstitution
••Electronegativity and size of A and B site cationsElectronegativity and size of A and B site cations
Optical properties designOptical properties design
Dyes and Pigments, 76 (2007) 70-75.
1212Materials Science&Technology
SrNbO2NTetragonal
Nb-(O,N)-Nb = 173°
Gap 1.9 eV
BaNbO2NCubic
Nb-(O,N)-Nb = 180°
Gap 1.8 eV
Ionic radii : Ba (1.61 A) > Sr (1.41 A) > La (1.18 A) > Ca (1.12 A)
Crystal structures, anionic composition, band gap
CaNbO2Northorhombic
Nb-(O,N)-Nb = 153°
Gap 2.1 eV
LaNbON2
orthorhombic
Nb-(O,N)-Nb = 160°
Gap 1.7 eV
Pnma Pm3m I 4/mcm Pnma
a
c
a
c
a
c
a
b
Band gap can be tuned by changing the structure distortion and N-content
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1313Materials Science&Technology
Photocatalyzed decomposition of simple organic molecules
Ceramic Materials Research Trends 2007
IR detector
Oxynitride
film
Reactor
vessel
KBr
window
Xe lamp UV filter IR spectrometer
IR detector
Oxynitride
film
Reactor
vessel
KBr
window
IR detector
Oxynitride
film
Reactor
vessel
KBr
window
Xe lamp UV filter IR spectrometer Xe lamp UV filter IR spectrometer
PhotocatalyticPhotocatalytic ScreeningScreening
1414Materials Science&Technology
dp
IRE
IRE, internal reflection element
Harrick, Internal reflection spectroscopy Interscience Publishers: New York (1967)
Bürgi, Baiker Adv. Catal. 50 (2006) 227
2000 180 0 1600 1400
a b s . u n i t s
wavenumber(cm-1)
Materials Science& Technology
UV-vis light •• HydrogenHydrogen productionproduction
–– waterwater splittingsplitting
–– alcoholalcohol decompositiondecomposition
•• MolecularMolecular mechanismmechanism @@ surfacesurface
–– TiOTiO22 andand otherother representativerepresentative photocatalystsphotocatalysts
–– effecteffect andand rolerole of noble metal (Pt, Pd, Au)of noble metal (Pt, Pd, Au)
solution
photocatalyst
i ni n s i t u s i t u ATR ATR --IRIR spectroscopyspectroscopy of solidof solid--liquidliquid interfacesinterfaces
Spectroscopy of photocatalysts (Spectroscopy of photocatalysts (DavideDavide FerriFerri))