catalysis research at superxas beamline...olga safonova. temporary staff: technicians: grigory....
TRANSCRIPT
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WIR SCHAFFEN WISSEN – HEUTE FÜR MORGEN
Catalysis research at SuperXAS beamline
Olga V. Safonova:: Operando Spectroscopy group :: Paul Scherrer Institute :: Switzerland
CONEXS meeting, Newcastle University, UK, 18th February 2020
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Operando spectroscopy group
joint project between Energy and Environment and Photon Science Divisions
Head:Maarten Nachtegaal
Senior scientists:
currently 1 postdoc and 5 PhD students
Olga Safonova
Temporary staff:
Technicians:
GrigorySmolentsev
Adam Clark StephanHitz
Urs Vogelsang
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• Catalysis and its importance
• X-ray spectroscopy for catalysis research
• SuperXAS beamline
• Research examples:
Active phase in oxygen evolution electrocatalyst
Selective catalytic reduction of NOx on Cu-species in zeolite
Oxygen activation on Cu-CeO2 catalyst
Outlook
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Catalysis
OO
CO
C
O
O OC
O
+O CO O
C
O
O
2. reaction
3. separation(desorption)
Pt surface = catalyst
1. binding (adsorption)
• Catalyst accelerates chemical reaction without being consumed
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Catalysis and energy
Reaction coordinate
Free
ene
rgy Ea
Ea
• Catalyst offers more energetically favorable reaction pathway
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Application of catalysis
• More than 85 % of chemicals are produced with a help of catalysts
• Catalysts clean car and industry exhausts
• Electrocatalysts produce zero emission hydrogen fuel
• Catalysts are widely used in pharmaceutical industry
CCI France Chine
National Chemical laboratory
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Structure of catalysts
• Homogeneous catalysts: molecules in solution
• Heterogeneous catalysts: active component is dispersed on the surface of a high surface areasupport, pressed into pellets and filled into reactor
• Electrocatalysts:high surface area materials deposited on an electrode
Oxygen
Water
OH-
OH-
OH-
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Relevant length scales in catalysis
X-ray absorption spectroscopy (XAS)(structure of active site on the atomic scale)
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Ex situ, in situ and operando spectroscopy
Ex situ(catalyst removed from reactor)
In situ(catalyst under specific conditions)
Operando (catalyst under working conditions)
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X-ray spectroscopy allows uncoveringstructure – activity relationships
Structure (XAS and XES)
Reactants ProductsActivity
(MS,GC, IR..)
• no material and pressure gaps• quantitative information about activity • quantitative/element specific structural information
Operando reactor
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beamline
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beamline
5-crystal Johann spectrometer
Solid state detector
Quick-XAS monochromator
Si (111) and Si(311)
sample
I0
I1
Pilatus detector
Von Hamos spectrometer
Pilatus/Mythen detector
fs laser
PIPS diode
2.9 T Superbendsource
Energy range: 4.5-35 keVFlux : up to 1x1012 ph/s (@ 12 keV) Spot size: from 100 x 100 µm2 to 5000 x 500 µm2
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Quick XAS at SuperXAS
2.9 T Superbendsource
Flux at SLS Superbendsource (2.9 T)
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Quick XAS monochromator
Quick-XAS monochromator
Direct drive torque motor oscillating channel-cut monochromator
O. Muller et al. REVIEW OF SCIENTIFIC INSTRUMENTS 86, 093905 (2015)
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How is Time-Resolution Achieved?
I0I1
Gridded Ionization Chambers
O. Muller et al. Journal of Physics: Conference Series2013 vol: 425 (9) pp: 092010
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Time resolution
10ms achievable time-resolution
O. Muller et al. J. Synchrotron Rad. (2016). 23, 260–266
Follow chemistry in action
Chemical reaction is triggered at t = 0 s by fast injection of a chalcogenesource.
Where does this leave us?
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Research example 1:
Structure of active phase in oxygen evolution electrocatalyst
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Oxygen
Water
OH-
OH-
OH-
• Ba0.5Sr0.5Co0.8Fe0.2O3-d perovskite
Oxygen evolution electrocatalyst
• Alkaline fuel cell
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An oxygen permeation membrane material
Why Ba0.5Sr0.5Co0.8Fe0.2O3-d was chosen?
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Fabbri et al. ACS Catalysis , 2014, 4 ,1061, Fabbri et al., Adv. Energy Mater. 2015, 5, 1402033
Addition of carbon improves oxygen evolutionactivity of Ba0.5Sr0.5Co0.8Fe0.2O3-d
with carbonmore active
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Co K-edge
Ex situ Co K-edge XANES
Addition of carbon
Co2+ is the active state?Fabbri et al. ACS Catalysis , 2014, 4 ,1061, Fabbri et al., Adv. Energy Mater. 2015, 5, 1402033
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Ex situ Co K-edge XANES: higher Co2+ fractionmakes better catalyst
SG: sol gel methodFS: flame spray method
Fabbri et al. Nature Materials, 2017, 16, 925
~55X
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Operando cell for XAS
X-Ray window
Binninger et al., J. Electrochem. Soc. 2016
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Operando Co K-edge XANES:Co2+ oxidizes into Co3+ under operationconditions and activity increases
Fabbri et al. Nature Materials, 2017, 16, 925
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Operando Co K-edge EXAFS
• For highly oxygen deficient perovskites, a Co-Co scattering peaks appears at 2.8-3.2 Å• Under operando conditions Co-Co contribution at 3.2 Å decreases and at 2.85 Å typical
of the CoO(OH) structure increases
Fabbri et al. Nature Materials, 2017, 16, 925
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CoO(OH)
CoO(OH) is active phase
Fabbri et al. Nature Materials, 2017, 16, 925
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Performance comparison of BSCF-FS and IrOx under operating conditions.Polarization curves (A) and voltage vs. time at the steady state current density of 200
mAcm-2 (B) obtained for membrane electrode assemblies (MEAs) MEAs having BSCF-FS and IrOx as anodic electrode.
Fabbri et al. Nature Materials, 2017, 16, 925
This catalyst is more active than the benchmark IrO2 catalyst and is very stable
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Research example 2:
Selective catalytic reduction of NOx on Cu-species in zeolite
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Selective Catalytic Reduction (SCR) of Nitrogen Oxides with Ammonia
Research example 2:
Selective catalytic reduction of NOx on Cu-species in zeolite
4𝑁𝑁𝑁𝑁 + 𝑁𝑁𝐻𝐻3 + 𝑁𝑁2 → 4𝑁𝑁2 + 6𝐻𝐻2𝑁𝑁
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A Consistent Reaction Scheme for the Selective Catalytic Reduction of Nitrogen Oxides with Ammonia
Ton V. W. Janssens et al. ACS Catal. 2015, 5, 2832−2845
Selective catalytic reduction of NOx on Cu-species in zeolite
ReductiveO
xida
tive
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Time-resolved copper speciation during selective catalytic reduction of NO on Cu-SSZ-13
Dynamic copper speciation
A. Marberger et al. Nature catalysis, 1, 2018, 221–227
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Relevant time scales in chemistry and catalysis
10-12 10-9 10-6 10-3 110-18 10-15 103 s
Reaction kinetics
Fundamental Applied
Bond breaking/ formation Stability,
deactivation
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Active site structure during catalytic cycle
TS1
TS2
TS3
Reaction coordinate
Free
ene
rgy
Ea
I1 I2
I3 I4 I5
Long-lived intermediate
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CO oxidation
𝐶𝐶𝑁𝑁 + 𝑁𝑁2 → 𝐶𝐶𝑁𝑁2Pt/CeO2 , 80 oC [1]
Methanol synthesis
𝐶𝐶𝑁𝑁/𝐶𝐶𝑁𝑁2 + 𝐻𝐻2 → 𝐶𝐶𝐻𝐻3𝑁𝑁𝐻𝐻
CuZn/Al2O3 , 260 oC , 25 bar [4]
Fischer-Tropsch synthesis𝐶𝐶𝑁𝑁 + 2𝐻𝐻2 → 𝐶𝐶𝐻𝐻2 𝑛𝑛 + 𝐻𝐻2𝑁𝑁
Co/Al2O3, 210 oC , 35 bar [3]
Selective alcohol oxidation
𝑅𝑅𝑁𝑁𝐻𝐻 + 𝑁𝑁2 → 𝑅𝑅𝐻𝐻𝑁𝑁
AuPd/TiO2, 160 oC [2]
Ammonia synthesis
3𝐻𝐻2 + 𝑁𝑁2 → 3 𝑁𝑁𝐻𝐻3Ru surface, 450 oC, 100 bar [6]
Ethylene hydrogenation
𝐶𝐶2𝐻𝐻4 + 𝐻𝐻2 → 𝐶𝐶2𝐻𝐻6Pt nanoparticles , 60 oC [5]
Alkene metathesis𝑅𝑅1 𝐶𝐶 = 𝐶𝐶 𝑅𝑅2 → 𝑅𝑅1(2) 𝐶𝐶 = 𝐶𝐶 𝑅𝑅1(2)
W/SiO2, 70 oC [7]
Time (s)10-310-6 1[1] Science, 2012, 341,771
[2] Science, 2006, 311, 696
[3] JACS, 2006, 128, 3956
[4] Nature Comm., 2016, 7, 13057
[5] J. Catal., 127, 342
[6] Nature Chem., 2009, 1, 37
[7] Central Sci., 2016, 2, 569
Relevant time scales based on turn-over frequencies (TOF)
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Time-resolved copper speciation during selective catalytic reduction of NO on Cu-SSZ-13
Dynamic copper speciation
XAS probes the oxidation state and coordination geometry of Cu
1 Hz monochromator oscillation frequency(500 ms per full XAS spectrum)
A. Marberger et al. Nature catalysis, 1, 2018, 221–227
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Dynamic copper speciation
A. Marberger et al. Nature catalysis, 1, 2018, 221–227
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Dynamic copper speciation
A. Marberger et al. Nature catalysis, 1, 2018, 221–227
8980 9000 9020
0.0
0.2
0.4
0.6
0.8
1.0
1.2
8980 9000 9020 8980 9000 9020
CuII(NH3)4norm
aliz
ed a
bsor
ptio
n / a
.u. time = 0s
CuI(NH3)2
(a) (b)
CuII(NOx)y
time = 75s
energy / eV
DataFit
(c)
CuII-Z
time = 940s
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0.0
0.2
0.4
0.6
0.8
CuI(NH3)2 CuII(NH3)4 CuII(OH)2 CuII-Z CuII(NOx)z
LC fi
t wei
ghts
/ a.
u. (a)NH3 on
0 400 800 12000
200
400
600
800
1000
time / s
conc
entra
tion
/ ppm (e)
NH3
NO
NH3 on (b)
0 400 800 1200
NO
NH3
225°C
time / s
(f)
190°C
(c)NH3 on
0 400 800 1200
400°C
time / s
(g)
NH3
NO
(d)
NH3 on
0 400
275°C
time / s
(h)
NH3
NO
Dynamic copper speciation
A. Marberger et al. Nature catalysis, 1, 2018, 221–227
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Increased NO conversion and reduced NH3 slip with controlled feeding of ammonia
A. Marberger et al. Nature catalysis, 1, 2018, 221–227
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Take home messages
• Operando methodology allows identifying active sites structure
• Time-resolved XAS methods help to uncover true reaction intermediates and distinguish them from spectators
• XAS methods uniquely allow for quantitative correlations between catalytic rates and the reactivity of true active sites