structural diagnostics of functional ... - elch.chem.msu.rumolecular aspects of electrochemistry,...

Structural diagnostics of functional materials in action: capabilities of

X-ray synchrotron techniquesYan Zubavichus

National Research Centre «Kurchatov Institute», Moscow, Russia

Molecular Aspects of Electrochemistry, Dubna, 26-31 August 2012

2

Scope of the lecture• Introduction to synchrotron radiation (SR)• Scheme and capabilities of the Structural

Materials Science beamline at the KurchatovSR source

• Experiments aimed at techniques development• Examples of combined structural studies of

complex materials


3

Synchrotron Radiation

Electromagnetic radiation generated by ultrarelativisticelectrons/positrons traveling along circular orbits in accelerators of light charged particles (e-/p+)


4

Advantages compared to standard X-ray sources

• Intensity/Brightness higher by 6-10 orders of magnitude

• Continuum spectrum from IR to hard X-rays

• High natural collimation• Tunable polarization• Partial coherence


5

10.50 10.75 11.00 11.25 11.50 11.75 12.00

Pt L3

Re L2

Fluo

resc

ence

Yie

ld

Photon Energy, keV

Re L3

Diffraction

Spectroscopy

Synchrotron X-ray techniques

Imaging

Mixed and combined techniques (anomalous scattering, microspectroscopy, etc.)


6


7

Synchrotron sources in RussiaSiberian Center for Synchrotron Radiation (Budker Institue for Nuclear Physisc, Novosibirsk) in operation since mid 1970-iesStorage rings VEPP-3 (2 GeV, 120 mA), VEPP-4 (5 GeV, 40 mA) – both 1st generation (ε~300 nm·rad)11 beamlines ssrc.inp.nsk.su

Kurchatov Synchrotron Radiation Source (NRC «Kurchatov Institute», Moscow) in operatiionsince early 2000-iesSiberia-1 (booster, 450 MeV) – 3 VUV beamlinesSiberia-2 – dedicated 2nd generation source (2.5 GeV, 300 mA, ε ~75 nm·rad), 16 beamlineswww.kcsr.kiae.ru

Zelenograd Synchrotron Radiation Facility (Lukin R&D Institute of Physical Problems), http://www.niifp.ru – under construction

Dubna Electron Synchrotron (JINR) http://wwwinfo.jinr.ru/delsy – project development

International collaboration:Russian-German beamline at BESSY II http://www.bessy.de/lab_profile/04.rglab/.RGLabRussian involvement in ESRF consortium (since July 2011)Russian participation in European XFEL project (scheduled start in 2014, 4th generation source)


8

Kurchatov Synchrotron Radiation CentreX-ray stations

1 Protein Crystallography

2 Precision X-ray Optics

3 X-ray Crystallography and Physical Materials Science

4 Medical Imaging

6 Energy-Dispersive EXAFS

7 Structural Materials Science (SMS)

8 X-ray Small Angle Diffraction Cinema (bioobjects)

9 Refraction Optics & X-ray Fluorescence Analysis

10 X-ray Topography & Microtomography

VUV stations11 X-ray Photoelectron Spectroscopy

12 Optical spectroscopy for Condensed Matter

13 Luminescence & Optical Investigations

Technological stations 14 X-ray Standing Waves for Langmuir-Blodgett Films

15 Molecular Beam Epitaxy

16 LIGA


9

Structural Materials Science beamline

• In the user mode since 2004 • Techniques implemented: XANES/EXAFS, XRD,

SAXS• Mission: combined multitechnique X-ray diagnostics of

non-crystalline and nanostructured functional materials

• Objects: supported catalysts, metal/polymer hybrids, metal glasses and alloys, transition metal cluster and coordination compounds, colloidal suspensions


10

SMS : optical scheme

SRPhoton energy range5-19 keV with Si(111)8-35 keV with Si(220)ΔE/E~2×10-4

Beam size3×3 mm2 down to ~10×10 mkm2

Scattered vector (s) rangeSAXS 0.001 ÷ 6 Å-1

XRD 0.2 ÷ 20 Å-1

Photon flux~0.5×108 ph/mm2/s 10-4 Δλ/λ

1 2

3 45

6

7

8 9

10

11

12

14

13 15

1, 3, 9 motorized slits2 channel-cut monochromator4,5,8,13 ionization chambers6 Sample environment chamber with

control of gas and temperature 7 1D bent detector for in situ diffraction10 Fluorescence detector11 Vacuum chamber for SAXS12 Imaging Plate for high-quality diffraction14 1D position sensitive detector for SAXS15 Transmitted beam position monitor


11

Modes of measurements

transmissionXAFS

in situ time-resolveddiffraction

FluorescenceXAFS

SAXS

Structural diffraction


12

Most demanded measurements: transmission XAFS with an

autosampler

Autosampler with a holder for 9 samples

Reference sample for the energy scale calibration

(metal foil)

Ionization chambers


13

Sample temperature control20-550оСChromel-alumel (Type K) thermocouple

N2, cold gasor liquid

Limited capabilities for temperature variation:

-120оС or-196оС

CoolingFrom 500oC down to -120oC ~ 1 hour

Thermostabilization

±1оС

4 × 350 W


14

Closed-cycle He-refrigerator

The minimum temperature reached 5.5К + precise temperature variation up to room temperature


15

Gas inlet system• Three-component mixtures• Inert gases: He, N2, Ar• Redox processing: O2, H2

• Catalytic substrates: CO, CH4

Compressedgas vessels

VacuumeterFlow-mass controllers

Mixing

chamber

In-situchamber

Pump


16

Combined use ofXAFS, XRD and SAXS

• XANES - oxidation state of heavy atoms + coordination symmetry

• EXAFS - local neighborhood of a given heavy atom

• XRD - long-range order, phase composition, size of crystallites

• SAXS - size and shape of nanoparticles or pores in a range of 1-100 nm


17

X-ray absorption spectroscopy: basics

Pre-edgeregion

Near-edge fine structure XANESExtended oscillatory structure (EXAFS) (50-

1000 eV above the edge

Absorption edge

E0

Pre-edgeregion

Near-edge fine structure XANESExtended oscillatory structure (EXAFS) (50-

1000 eV above the edge

Absorption edge

E0


18

FermilevelHOMO

LUMO

XANES: originXANES: originVacuum

level

Core electronlevel

Valenceband

Forbidden gap

Conductionband

XANES probes the energy distribution of certain symmetry-allowed MOs or DOS features above the Fermi level

Fermi‘s golden rule:μ ~ |<f | V | i >|2 , f,i – wave functions of the final and initial states, V – dipole moment operator


19

Photoionized atomNeighbor atom

Photoelectron wave

Back-scattered photoelectronwave

Single scattering

Multiple scattering

EXAFS: originEXAFS: originInitial state: electron on the core levelFinal state: outgoing photoelectron wave

Local-structrure parameters of the central atom can be retrieved from EXAFS

Interference


20

)(/222

22

))(2sin(),()(

)( krkjjj

j j

j jj eekkrkfkr

NkSk λσϕπχ −−+= ∑

χ - normalized background-subtracted EXAFS-signalk – photoelectron vector modulus (≡2π/ λ)S – Extrinsic loss coefficient (0.7-1.0)N – coordination number in the j-th coordination spherer – interatomic distancef – backscattering amplitudeϕ – phase shiftσ– Debye-Waller factorsλ− photoelectron mean-free path


21

Techniques development

• Complementary utilization of XAFS, SAXS andXRD in structural diagnostics of complex poorly ordered materials

• Structural diagnostics of functional materials in situ under operational conditions

• Online structural monitoring of dynamical processes (phase transitions, chemical reactions)

• Local-sensitive microbeam techniques applied to microheterogeneous specimens


22

Experiments aimed at techniques development

• Time-resolved diffraction

• Spatially resolved diffraction

• XAFS monitoring of chemical reactions in aqueous solutions


23

Pd acetate reduction with molecular hydrogen

Pd K-edge EXAFS

Evolution of the diffraction patternexposure 1 min)

PdPdHx

Pd

PdHx

Pd

PdHx

Pd K-edge XANES

24350 24400 24450

Pd(OAc)2

Pd PdHx

μ

E, eV

0 2 4 6

Pd-Pd Pd(OAc)2

Pd PdHx

|FT(

k3 χ(k)

)|

R, Å

Pd-O


24

Ta inserts

Nb3Sn/Cu

Cu

Nb diffusion barrier layer

Nb3Sn/Cu

Cu

Nb

A perpendicular cut

A parallel cut

Morphology of LTSC Nb3Sn-wires(in a collaboration with Prof. E.A. Dergunova, et al., VNIINM)


25

X-ray Tomographic reconstruction (R.A. Senin, A.S. Khlebnikov)


26

10 20 30 40 50 600

200

400

10 20 30 40

0

2

4

6

444 721

610

333422440332421

420

hkl - Nb

420331

400

400

311

hkl - Cu

600611

222

111

220

200

321

320

222

211210

200

hkl - Nb3Sn

I, a.

u.

2θ, deg

110

520521 630

631

720

211

111

I, a.

u.200


27

10 20 30 40

0

20

40

60

80

I, a.

u.

2θ, deg

Spot 2

Nb(110)

Nb(110)

X-ray diffraction mapping of the heterogeneous sample

(beamsize ~150 μm)1

2

3

4

5

100 μm


28

12

3

4

5

100 мкм

10 20 30 40

0

20

40

60

80

100

120

140

160

180

I, a.

u.

2θ, deg

Spot 4

Only strongly textured Cu


29

12

3

4

5

100 мкм

10 20 30 400

20

40

60

80

I, a.

u.

2θ, deg

Spot 5

Nb(110)

Nb(110)


30

2.4 2.6 2.8 3.0

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Nb(110)

Nb3Sn(211)Nb3Sn(210)

Nb3Sn(200)

I, a.

u.

4πsinθ/λ, Å-1

Cu(111)

The use of anomalous diffraction to emphasized the contribution of Nb-phases


31

38 40 42 44

Cu(311)

Nb3Sn(332)

Nb3Sn(421)

Nb3Sn(420)

I, a.

u.

2θ, o

RT 6.5 K 40 K

Nb3Sn(410)

Low-temperature diffraction study

No structural phase transition

cubic →tetragonal

RT 40 6.5 Cu 3.6058 3.5967 3.5957 Nb3Sn 5.25 5.24 5.23


32

Redox chemistry of Br-containing aqueous solutions from Br K-edge

XANES


33

13450 13500 135500.0

0.5

1.0

1.5

2.0

2.5

μ, a

.u.

Photon energy, eV13450 13500 13550

0.0

0.5

1.0

1.5

2.0

2.5

μ, a

.u.

Photon energy, eV

13450 13500 135500.0

0.5

1.0

1.5

2.0

2.5

μ, a

.u.


0.0

0.5

1.0

1.5

2.0

2.5

μ, a

.u.

Photon energy, eV

13450 13500 135500.0

0.5

1.0

1.5

2.0

2.5

μ, a

.u.


0.0

0.5

1.0

1.5

2.0

2.5

μ, a

.u.

Photon energy, eV

NaBrO3 (solid) NaBrO3 (aq.)

KBr (solid) KBr (aq.)

1NaBrO3:5KBr (aq.) +H+ (Br2)

BrO3- + 5Br- +6H+ →3Br2 + 3H2O


34

13450 13500 135500.0

0.5

1.0

1.5

μ, a

.u.

Photon energy, eV

Composition of the mixture: linear combination fit

19% NaBrO3 + 81% KBr

(1:5 ≡ 17:83)


35

Examples of combined studies of complex

materials• Pd/Cu catalysts for the mild CO oxidation

• Water-soluble Al activated with Ga85In15eutectic alloy


36

(Pd,Cu)Clх/γ-Al2O3 catalysts for the mild CO oxidation

(in a collaboration with L.G. Bruk)


37

Series of samples studied• Starting reagents CuCl2⋅ 2H2O and PdCl2• Impregnation solutions CuCl2 and CuCl2-PdCl2• Pure support γ-Al2O3• Model systems CuCl2/γ-Al2O3 , PdCl2,KCl /γ-Al2O3• Actual catalyst PdCl2,CuCl2/γ-Al2O3 “as is”• Catalyst PdCl2,CuCl2/γ-Al2O3 under action of CO (only СО, СО+Н2О, СО+H2O+O2)

Problems addressed by the structural study• The chemical nature of active sites• The mechanism explaining the synergism in the Cu

and Pd catalytic activity


38

10 20 30 40

I, усл.

ед.

2θ, o

CuCl2/γ-Al2O3

CuCl2,PdCl2/γ-Al2O3

Paratracamite, model

γ-Al2O3

The genesis of active sites: XRD

Cu2+ is adsorbed on γ-Al2O3 from CuCl2aqueous solutions as polycrystalline paratacamiteCu2Cl(OH)3

Palladium is “diffraction-silent”


39

0 1 2 3 4 5

Catalyst "as is"

CuCl2 + PdCl2 (aq.)

|FT(

k3 χ(k)

)|

R, Å

CuCl2 2H2O (solid)

The genesis of active sites: Cu K-edge

EXAFS

Sample Coord. sphere N R, Å σ2, Å2 ΔE, eV Rf CuCl2⋅2H2O Cu-O

Cu-Cl Cu…Cl

222

1.95 (1.94)*2.27 (2.28) 2.86 (2.93)

0.00450.00350.0148

2.5 0.030

Solution 1 (CuCl2) Cu-Oeq Cu-Oax

42

1.97 2.29

0.00430.0210

0.6 0.021

Solution 2 (CuCl2, PdCl2) Cu-Oeq Cu-Oax

42

1.97 2.30

0.00440.0203

0.7 0.018

Cu/γ-Al2O3 Cu-O1 Cu-O2 Cu...Cl

Cu...Cu1 Cu...Cu2

23142

1.99 (1.98) 2.05 (2.11) 2.85 (2.79) 3.09 (3.06) 3.47 (3.41)

0.00260.02660.00650.01860.0093

0.4 0.016

Cu,Pd/γ-Al2O3 Cu-O1 Cu-O2 Cu...Cl

Cu...Cu1 Cu...Cu2

23142

1.99 (1.98) 2.09 (2.11) 2.89 (2.79) 3.09 (3.06) 3.47 (3.41)

0.00280.04000.00720.01570.0116

1.2 0.016

CuCl2.2H2O

Cu2Cl(OH)3


40

0 1 2 3 4 5

PdCl2 CuCl2, PdCl2

(aq. solution) Cu,Pd/γ-Al2O3

|FT(

k3 χ(k)

)|

R, Å

Sample Coord. sphere N R, Å σ2, Å2 ΔE, eV Rf PdCl2 Pd-Cl

Pd...Pd Pd…Cl Pd...Pd2

Pd-Cl-Pd-Cl

44112

2.29 (2.30-2.31)*3.28 (3.28-3.33)

3.37 (3.34) 3.72 (3.77)

4.57 (4.60-4.62)

0.00270.01460.00130.00400.0026

4.5 0.007

Solution 2 (CuCl2, PdCl2) Pd-Cl Pd-Cl-Pd-Cl

42

2.28 4.56

0.00220.0050

4.85 0.030

Cu,Pd/γ-Al2O3 Pd-Cl1 Pd-Cl2

31

2.26 2.36

0.00150.0015

2.9 0.019

The genesis of active sites: Pd K-edge EXAFS

β-PdCl2 (Pd6Cl12)Pd is adsorbed on γ -Al2O3 from aqueous solutions ofPdCl2 as isolated square-planar [PdCl4]2- anionsNo specific interactions Cu…Pd are observed


41

0 1 2 3 4 5

Catalyst

300 K 6 K

|FT(

k3 χ(k)

)|

R, Å

PdCl2

Pd...Pd

Low-temperature EXAFS study


42

In-situ reduction of the catalyst in humid CO (at RT): Pd K-edge

XANES


43

In-situ reduction of the catalyst in humid CO (at RT): Pd K-edge EXAFS

Pd-Cl

Pd-Pd


44

Catalyst “as is”Catalyst+CO

Al2O3

2-1

3-2

In-situ reduction of the catalyst in humid CO (at RT): XRD


45

In-situ reduction of the catalyst in humid CO (at RT): Cu K-edge XANES and EXAFS

Only 10-15% of copper in the catalyst undergoes chemical modification Cu2+ →Cu+

(spatial proximity effect of Pd)


46

Al (any industrial alloy) ⎯⎯⎯⎯⎯⎯⎯→ Alact ⎯⎯⎯⎯⎯⎯→ AlOOH/Al(OH)3 + H2Ga85In15-eutectics H2O (RT, no promotors)

Activated Al for the small-scale hydrogen energetics


47

10 20 30 40 50 60

After H2O

Deactivated Al

Active Al

Pristine Al

In

Ga85

In15

eut.

I, усл.

ед.

2θ, o

Ga

39 40

Active Al

I, усл.

ед.

2θ, o

Pristine Al

(220)

Diffraction data


48

10375 10400 10425

5

3

2

4

μ,

усл

. ед.

E, эВ

1

1 – Ga foil, 2 – Ga-In eutectic alloy, 3 – activated Al, 4 - active Al after H2O, 5 –deactivated A

0 1 2 3 4 5 6

Ga-Ga,Al5

3

2

4

|FT(

k3 χ(k)

|

R, Å

1

Ga-O

Ga K-edge XANES/EXAFS data


49

Ga foil:N sphere R σ2

1 Ga-Ga 2.514 Ga-Ga 2.68 0.00972 Ga-Ga 2.80

Ga-In eutectics:N sphere R σ2

1.7 Ga-Ga 2.68 0.0026

Active Al:N sphere R σ2

1.7 Ga-Ga 2.70 0.00261.2 Ga-Al 2.80 0.0011

2 3 4 5 6 7 8 9 10 11 120

1

2

3

4

5

R, Å

k, Å-1

Ga-Ga

2 3 4 5 6 7 8 9 10 11 120

1

2

3

4

5

R, Å

k, Å-1

Ga-Ga

2 3 4 5 6 7 8 9 10 11 120

1

2

3

4

5

R, Å

k, Å-1

Ga-Ga

Ga-Al

Wavelet maps


50

250 μm

100 μm

Imaging (X-ray microscopy + tomography)

Pristine Al Active Al

Cross-section corresponding to the geometrical centre of the sample


51

Liquid eutectics

Activation mechanism: bulk diffusion of GaIn-eutectics along intergrain boundaries promoted by the emergence of (Al-Ga-In) solid solution in the

subsurface layers of Al crystallites

Deactivation mechanism: decomposition of the eutectic alloy giving rise to a partial oxidation of Ga

and crystallisation of In

(Al-Ga-In) solid solution

Bulk polycrystalline Al

Fast diffusion transport


52

Conclusions• Синхротронное излучение – мощный инструментструктурной диагностики сложныхслабоупорядоченных материалов

• Станция «Структурное материаловедение» вчисле других станций КИСИ готова к проведениюрутинных исследований (и обладаетуникальными в масштабах России опытом итехническими возможностями)

• Мы открыты к сотрудничеству с любымигруппами как в вопросах проведения измерений, так и реализации новых методик / модернизацииоборудования


53

Laboratory for structural studies of non-crystalline materials, Kurchatov NBICS center, NRC «Kurchatov Institute»: Olga Beliakova, Aleksey Veligzhanin,

Elena Guseva, Vadim Murzin, Evgeniy Khramov, Alfred Chernyshov, Aleksandra Shulenina

structural diagnostics of functional ... - elch.chem.msu.rumolecular aspects of electrochemistry,...

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