2017/8/29

1

A SPring-8 New Beam Line for the Fuel Cell Analysis

Kiyotaka Asakura(ICAT,HU), Tomoya Uruga(SPring-8), Yasuhiro Iwasawa(UEC)

Supported by NEDO and partially JSPSSpecially thanks to Prof. S. Takakusagi, Y. Wakisaka, Y. Uemura, O.Sekizawa, D.Kido, N.Sirisit, Q.Yuan Prof Wadayama, Todoroki

Target of beamline BL36XU is Fuel cell for Cars

2

Membrane electrolyte assembly (MEA)

H2

AnodeCatalyst

CathodeCatalyst

MEA

O2

H2O

Electricity

Polymer electrolyte fuel cell (PEFC)

No CO2 nor NOX emission

O2 + 4H+ + 4e– 2H2O2H2 4H+ + 4e–

Fuel Cell Car is now sold but still expensive 3

¥8,000,000 $57,500!!

Why so expensive? Because Pt is used.

NEDO Road Map for Hydrogen and Fuel Cells4

NEDO project to commercialize the fuel cell car till the 2020.

To reduce the Pt amount, the life time (x 10) and efficiency ( x 10) of Pt catalysts. Cost cut for Pt catalyst.

To attain the purpose, structures of Pt catalysts and mechanisms must be studied under working conditions.

XAFS is a good technique to study the Pt catalysts under the working conditions.

5BL36 XU in SPring -8

SPring-8 BL36XU– BL36XU was constructed at SPring-8 and opened to users in

January 2013

Target of the project– Development of catalysts for the next generation polymer

electrolyte fuel cells(PEFC)

Target of beamline– Clarification of reaction and degradation process of

electrode catalysts of PEFCs under real working conditions by synchrotron radiation-based multi-analytical method(time- and spatially resolved XAFS, XRD, XES, AP-HAXPES)

– Open for all who are interested in fuel cell problems and related issues.

6

2017/8/29

2

Layout of BL36XU

7

K-B mirrors

Experimental stage

Tapered Undulator Optics hutch

Front end

M2: horizontal focusing mirror

M1: horizontal deflection mirror

M3, M4: vertical focusing mirrors

Servo motor driven monochromators

Experimental hutch

Fuel cell

Gas supply & treatment system

PEFC control system

[1] O. Sekizawa et al., J. Physics: Conf. Series, 430, 012020 (2013).

77 m

Radiation shielding wallRadiation shielding wall

Storage ringStorage ring

0 m

Experimentalhutch

Experimentalhutch

undulatorTapered

undulator

Frontend

Frontend

Optics hutchOptics hutch

Si(111) and Si(220)

Temporal- and spatially resolved XAFS method at BL36XU [1]Energy range: 4.5 ~ 35 keVTime resolution: 100 μs (Energy dispersive XAFS)

2 ms (Quick scanning XAFS)Spatial resolution: 100 nm (3D scanning microscopic XAFS imaging)

1 μm & 50 nm (3D full-field XAFS imaging)

SR-based analytical methods for PEFC

8

SystemMinimum resolution

FeatureTemporal 2D 3D

QXAFS with servo motor driven Mono 10 ms 100 nm - Base system

QXAFS with galvano motor driven Mono 2 ms 100 nm - Fast XANES

DXAFS 100 μs 200 μm - Ultra fast, model sample

Time-resolved QXAFS/XRD 60 ms 100 nm - Sequential XAFS/XRD

2D scanning microscopic XAFS imaging 30 min 100 nm - Dilute sample

2D transmission QXAFS imaging 1 min 1 μm - Time-resolved 2D image

3D full-field XAFS imaging 1 hr/ 5 hr - 1 μm / 50 nm

3D chemical state imaging

XES (HR-XANES/RIXS) 1 min/ 1hr 200 μm - Adsorption species

Ambient pressure HAXPES 10 min 10 μm - 100 kPa max.

In-situ multi-analytical measurement system for PEFC

9

FZP

PEFC

Capillary condenser

2D pixel detectorfor XRD

Diffracted X-ray

Transmission X-ray

Time-resolved QXAFS

Time-resolved XAFS/XRD

IncidentX-ray

1 mm 3D XAFSimaging

50 nm 3D XAFS imaging

2D X-ray image detector

2D X-ray image detector

Time resolved XAFS for in-situ PEFC

10

Sample

Ionization chamber

Fast angle scanning monochromator

WhiteX-rays

QXAFS

White X-rays Bent crystal

polychromator

Sample

Position sensitive detector

DXAFS

Ionization chamber

0.3

0.2

0.1

0.0

t

11.811.711.611.511.4

Photon energy (keV)

DXAFS (50 s) QXAFS (1 s)

Pt L3-edge XANES Pt/C catalyst in MEAPt: 0.6 mg/cm2

X-ray

MEA (Membrane Electrode Assembly)

GDL (Gas Diffusion Layer)

10 ms QXAFS using servomotor driven monochromator

11

Base system for XAFS measurements of BL36XU [1]High quality and stable XAFS measurement by high flux X-ray beam

Servomotor-drivenmonochromators [2]

k2-weighted Pt L3-edgeEXAFS oscillation

Sample: PEFC (0.5 mg-Pt/cm2)Measurement time: 20 ms

Si (111)4.5~28 keVSi (111)

4.5~28 keV

7~35 keVSi (220)7~35 keV

Narrow gapIonization chamber

Narrow gapIonization chamber

Switch

PEFCPEFCX-rayX-ray

In-situPEFC cell

Low noisecurrent amplifier

Narrow gapionization chamber

Electrodes gap: 3 mm

T. Sekizawa, et al., J. Phys. Conf. Ser., 712, 012142 (2016).2. Nonaka, et al., Rev. Sci. Instrum., 83, 083112 (2012).

Simultaneous operando time-resolved QXAFS/XRD

1

X-ray

TransmissionX-ray

PEFC

DiffractedX-ray

Narrow gapionization chamber

Two-dimensionalpixel detector

PILATUS 300K-W

[1] O. Sekizawa et al., ACS Sustainable Chem. Eng., 5, 3631 (2017).

Simultaneous QXAFS/XRD measurement by fast control of monochromatorTime resolution: 60 ms

20 ms XAFS × 2 + 20 ms XRD × 1

2017/8/29

3

Simultaneous operando time-resolved QXAFS/XRD

1

[1] O. Sekizawa et al., ACS Sustainable Chem. Eng., 5, 3631 (2017).

2D scanning microscopic XAFS imaging

1

X-ray detectorFluorescence

X-ray detector

high rigidityexperimental stage

high rigidityexperimental stage

xz stagesPiezo

xz stages

PEFC orSi membrane

PEFC orSi membrane

Switch

4.5 ~ 15keVRh-coated KB mirrors

4.5 ~ 15keV

Pt-coated KB mirrors15 ~ 35keV

Pt-coated KB mirrors15 ~ 35keVX-rayX-ray

Fast scanning microscopic XAFS

E6E5E4E3E2

XRF images

E1

Sample positioning stageHigh-accuracy high-speed piezo positioning XZ stage

Fast scanning microscopic XAFS [1,2]2-dimensional X-ray fluorescence (XRF) images are measured by fast scanning of a sample at each energy.It is could be applied to low concentration metal catalysts in PEFC.

[1] T. Tsuji et al., J. Phys.: Conf. Ser., 430, 012019 (2013).[2] O. Sekizawa et al., J. Phys. Conf. Ser., 712, 012142 (2016).

Profile of focused X-ray beam by KB mirror

X-ray energy: 25 keV

Same-view 2D scanning microscopic XAFS/STEM-EDS

15[1] S.Takao et al., J. Phys. Chem. Lett., 6, 2121 (2015).

0

1

2

11.55 11.57 11.59 11.61

Norm

alized

μt

Photon energy / keV

Area 1, Area 2Pt foil, PtO

Pt L3-edge XANES spectra

Area 1: PtArea 2: PtArea 1: Pt2+

Area 2: Pt0

TEM image observation

Electron / X-ray beam

STEM-EDS / nano XAFS

SiN window

100 μm

300 nm

100 μm

epoxy spacer spacer epoxy

Sliced sample Humid N2 gas

Si

Si

SiN membrane cell for XAFS/TEM

(1) TEM image (2) Edge jump

(3) White line peak intensity

2D mapping imageof sliced MEA

2.0

1.8

1.6

1.4

high

low

Same-view XAFS/STEM-EDS [1]Oxidation state of Pt by XAFS

Area 1: Pt2+

Area 2: Pt0

Elemental analysis by STEM-EDSArea 1: ionomer ratio is highArea 2: ionomer ratio is low

Oxidation state of Pt changes by ratio of Pt/ionomer

16

3D wide full-field transmission XAFS imaging

[1] O. Sekizawa et al., J. Phys. Conf. Ser., 849, 012022 (2017).[2] H. Matsui et al., Angew. Chem. Int. Ed., in pless (2017).

X-ray PEFC

Gas inletRotary joint

X-ray imagingdetector

Gas outlet

100 μm

3D Top view

Side view

Cathode GDL

Anode GDL

Cathode catalystPEMAnode catalyst

Wide full-field XCTFOV：～500 µmSpatial resolution：～1 µm

Reconstructed image of MEA in PEFC after activating

Catalyst CA: Pt/C, AN: Pd/CCell voltage: 0.4 VAN gas: N2, CA gas: H2

Temp.: 80℃

RGB displayRed: Pt contentBlue: Oxidation state of PtGreen: GDL, Anode catalyst, PEM

PTRF-XAFS(polarization-dependent total reflection fluorescence XAFS)

parallel bonds

E: electric vector

polarizedx-ray

slitsionizationchamber(I0) detector

single crystal surface

SR

ionizationchamber(I)

polarizedx-ray

slitsionizationchamber(I0) detector

single crystal surface

SR

ionizationchamber(I)

perpendicular bonds

EX-ray

EX-ray

Polarization dependence of EXAFS

3D structure of highly dispersed metal species on singlecrystal surface can be determined by measuring polarizationdependent fluorescence EXAFS in total reflection mode.

PTRF-EXAFS

EXAFS oscillation derived from i-th scattering atom; χ

edges) ( )cos9.07.0)(( 3,22 Lk

iii

edges) and ( cos)(3)( 21LKkk

iii

Fluorescence detection→enable to detect ~1013 atoms / cm2

Total reflection mode→ X-ray penetration depth decreases to a few nm.

Ri

Polarization dependent XAFS

1. Pt layer (30nm)/Ti (5nm)/ Φ1 inch Si wafer

SiPt

D1

Gafchromic film1

Pb 1

Gafchromic film2

Pb 2

φ

N2 in

N 2ou

t

inout

p-pol.

potential / V polarization rPt-Pt / Å

0.54 Vs-pol. 2.78p-pol. 2.77

0.01 Vs-pol. 2.78 p-pol. 2.78

–0.11 Vs-pol. 2.77p-pol. 2.76

0.54V ーー＞SO4 adsorption0.01 V UPD H -0.11 V Evolution H.

Changing the voltage and bond length

Detector

2017/8/29

4

Pt monolayer formation by Suface Limited Replacement Reaction(SLRR)

Au(core) –Pt(Shell)

Pt monolayer on Au surface

19

Figure 2 EXAFS comparison between experimental data and FEFFcalculation for the Pt/Au(111) at E=0.45 V. a) s-polarization b) p-polarization

3 4 5 6 7 8-0.10

-0.08

-0.06

-0.04

-0.02

0.00

0.02

0.04

0.06

0.08

0.10

k (1/Å)

(k)

EXP FEFF

a)

3 4 5 6 7 8-0.10

-0.08

-0.06

-0.04

-0.02

0.00

0.02

0.04

0.06

0.08

0.10

k (1/Å)

(k)

EXP FEFF

b)

Stereoscopic information

Ｓpol

P pol 30 % Pt one layer + 70 % PtCl42-

HOPG surface = good for a model system 20

PTRF-XAFS

Severe glancing condition for low Z element(Carbon)HOPG is not so flat in a macro level.Absorption of electrolyte is strong.

Why total reflection is necessary? BECAUSEWe have to reduce the elastic scattering from the bulk.

HOPG

E / eV

HOPG=highly oriented pyrolytic graphite

Backside illumination (BI)-XAFS21

I0

Ifluorescence

H. Uehara, K. Asakura,et al. Phys Chem Phys 16 (2014) 13748.

HOPG is used as a windowSince most of X-ray transmits through the HOPG . Small scattering from the window.

11520 11560 11600 11640

0.14

0.15

0.16

0.17

0.18

μt

photon energy / eV

For No electrolyte . Yes We Can!

1015 cm-2 Pt / HOPG in Air11520 11560 11600 11640

0.08

0.09

0.10

0.11

0.12

μt

photon energy / eV

Backside illumination with electrolyte22

Pt /HOPG in electrolyte

With Ge filter

Scattering from solventhinders the measurement.

A big scattering X-ray from electrolyte.

11520 11560 11600 11640

0.14

0.15

0.16

0.17

0.18

μt

photon energy / eV

Pt /HOPG in air

Fluorescence X-ray Energy Analysis

BCLA Bent Crystal Laue Analyzer

23

Cell

BCLASSD

I0If

1 × 1015 cm-2 Pt on HOPG(Highly oriented pyrolytic graphite)

Remove the bulk elastic scattering by Energy analysis

After BCLA1 Uehara, H. et al. In situ back-side illumination fluorescence XAFS (BI-FXAFS) studies on platinum nanoparticles deposited on a HOPG surface as a model fuel cell: a new approach to the Pt-HOPG electrode/electrolyte interface. Phys Chem Chem Phys 16, 13748-13754, doi:10.1039/c4cp00265b (2014).

E / eV

mt

H. Uehara, K. Asakura,et al. Phys Chem Phys 16 (2014) 13748.

11500 120000.00

0.05

mu

t

Photon Energy / eV

Pt L3 edge

Pt Alloy Nanoparticle by Ark Plasma Deposition

Collaboration with Dr. N.Todorokiand T.WadayamaS. Takahashi, N. Takahashi, N. Todoroki and T. Wadayama, Dealloying of Nitrogen-Introduced Pt–Co Alloy Nanoparticles: Preferential Core–Shell Formation with Enhanced Activity for Oxygen Reduction Reaction. ACS Omega. 1,1247-1252(2016).

1015 cm-2 Pt on HOPG(flat surface)

2017/8/29

5

PtAuCoN / HOPG

Au L3 edge appears at 9 A-1

25

Au L edge

Au L fluorescence is completely removed1. T. Kaito, H. Mitsumoto, S. Sugawara, K. Shinohara, H. Uehara, H. Ariga, S. Takakusagi, Y. Hatakeyama, K. Nishikawa and K. Asakura, K-Edge X-ray Absorption Fine Structure Analysis of Pt/Au Core–Shell Electrocatalyst: Evidence for Short Pt–Pt Distance. J.Phys.Chem.C. 118,8481–8490(2014).

26

Sample Scatterer N R Current /mA

Pt Loss(%)

Pt bC Pt 11.8 2.75Pt aC Pt 12.9 2.75 0.002 4.2

PtCo bC PtCo

8.23.0

2.732.61

PtCo aC PtCo

9.31.7

2.742.65

0.003 2.0

PtCoN bC PtCo

6.83.9

2.742.65

PtCoN ac PtCo

9.02.8

2.742.68

0.004 1.2

PtAuCoNｂｃ Pt(Au)Co

6.73.7

2.742.67

PtAuCoN ac Pt(Au)Co

9.52.6

2.742.67

0.012 0.4

27

Sample Scatterer N R Current /mA

Pt Loss(%)

Pt bC Pt 11.8 2.75Pt aC Pt 12.9 2.75 0.002 4.2

PtCo bC PtCo

8.23.0

2.732.61

PtCo aC PtCo

9.31.7

2.742.65

0.003 2.0

PtCoN bC PtCo

6.83.9

2.742.65

PtCoN ac PtCo

9.02.8

2.742.68

0.004 1.2

PtAuCoNｂｃ Pt(Au)Co

6.73.7

2.742.67

PtAuCoN ac Pt(Au)Co

9.52.6

2.742.67

0.012 0.4

Small leaching by nitrogen

In-situ XES (HR-XANES, RIXS) for in-situ PEFC

28

Bent crystal analyzer PEFC cell

2D detector

Incident X-ray

fluorescent x-ray

diffracted x-ray

0.０ V

1.0 V

0.4 V

0.5 V

11.570

11.565

11.560

Inci

dent

ene

rgy

(keV

)

1050

transfer energy (eV)

0

5

0

1050

1050

0.8 VXES of MEA in PEFC after activating

Pt LIII edgeCatalyst CA: Pt/C, AN: Pd/CCell voltage: 0.0→1.0 V→0.0 VAN gas: N2, CA gas: H2

Temp.: 80℃

RIXS2.5

2.0

1.5

1.0

0.5

0.0

norm

aliz

ed x

u(E)

11.580x10311.57511.57011.56511.560

photon energy (eV)

'0.13V' '0.4V' '0.6V' '0.8V' '0.9V' '0.93V' '0.97V' '1.0V'

Ge(660) for HR-XANES

Si(933) for RIXS

X-ray

PEFC

2D X-ray image detector

Ionizationchamber

Ionizationchamber

HR-XANES

Possibility of MARX-RAMAN

1. XAFS is element-specific. But it is not bond-specific.

Pt-C can not be distinguished from C in electrode.MARPE may be possible.

2. It is difficult to carry out in situ for Low-Z element.

N, C has to be measured in soft X-ray regions.X-ray Raman can do it .

Combination will make it possible to realize both.

29

. (A. Kay, C.S. Fadley, RMultiatom resonant photoemission: a method for determining near-neighbor atomic identities and bonding. Science. 281,679(1998). )

(K. Tohji, Y. Udagawa, Physical Review B 1987, 36, 9410-9412. )

MARX-RAMAN(Multi atom resonance X-ray Raman)30

MARX Raman

Resonant X-ray Raman

Vaccum level

X-rayEmission

Vaccum level Photoelectron

X-ray

Atom A Atom B. (A. Kay, C.S. Fadley, RMultiatom resonant photoemission: a method for determining near-neighbor atomic identities and bonding. Science. 281,679(1998). )

2017/8/29

6

Experimental setup31

MARX-RAMAN of TaN. 32

Temporal- and spatially resolved XAFS method at BL36XU [1]Energy range: 4.5 ~ 35 keVTime resolution: 100 μs (Energy dispersive XAFS)

2 ms (Quick scanning XAFS)Spatial resolution: 100 nm (3D scanning microscopic XAFS imaging)

1 μm & 50 nm (3D full-field XAFS imaging)

Summary

3

SystemMinimum resolution

FeatureTemporal 2D 3D

QXAFS with servo motor driven Mono 10 ms 100 nm - Base system

QXAFS with galvano motor driven Mono 2 ms 100 nm - Fast XANES

DXAFS 100 μs 200 μm - Ultra fast, model sample

Time-resolved QXAFS/XRD 60 ms 100 nm - Sequential XAFS/XRD

2D scanning microscopic XAFS imaging 30 min 100 nm - Dilute sample

2D transmission QXAFS imaging 1 min 1 μm - Time-resolved 2D image

3D full-field XAFS imaging 1 hr/ 5 hr - 1 μm / 50 nm

3D chemical state imaging

XES (HR-XANES/RIXS) 1 min/ 1hr 200 μm - Adsorption species

Ambient pressure HAXPES 10 min 10 μm - 100 kPa max.

Total Refletion Fluoresce e XAFS 10 hr 1mm 2 nm Stereo Structure

BIXAFS 10 hr 200 μm Stereo Structure, HOPG

MARX-RAMAN 24 hr 200 μm Bond specific