perovskite ctlyst and its uses

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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


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



2


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.


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 “ “



3


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


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.



4


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)


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



5


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


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



6


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.


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



7


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


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))

perovskite ctlyst and its uses

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