Nanosegregated Cathode Catalysts with Ultra-Low …...3.2 Carbon support vs. nanostructured thin...
Transcript of Nanosegregated Cathode Catalysts with Ultra-Low …...3.2 Carbon support vs. nanostructured thin...
2010 DOE Annual Merit Review
Nanosegregated Cathode Catalysts with Ultra-Low Platinum Loading
DE-PS36-08GO98010
PI: Nenad M. Markovic
Co-PI: Vojislav R. Stamenkovic
Announcement No:Topic: 1A
Materials Science DivisionArgonne National Laboratory
Project ID#FC008
This presentation does not contain any proprietary, confidential, or otherwise restricted information
Timeline
• Project end: 9/2012
Budget• Total Project funding $ 3.6M
• Received in FY09: $ 300KBarriers
Overview
• The main limitations: CATHODE
• Project start: 9/2009
~ 30-40% (!!!)Cathode kinetics
1) Durability (Pt dissolves: power loss)
2) High content of Pt = High Cost ($75/g)
3) Poor activity: Pt/C = Pt-poly/10
Subcontractors:
• Oak Ridge National Laboratory – Karren More• Jet Propulsion Laboratory – S.R. Narayan• Brown University – Shouheng Sun• Indiana University Purdue – Goufeng Wang• 3M Company – Radoslav Atanasoski
• DOE share: 80 %• Contractor share: 20%
• Funding for FY10: $ 564.4K
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DOE Technical Targets
• Durability w/cycling (80oC): 5000 hrs
• Cost*: $ 30/kWe
• Mass activity @0.9V: 0.44 A/mgPt
• PGM Total content: 0.2 g/kW
• Specific activity @0.9ViR-free: 720 µA/cm2
• Electrochemical area loss: < 40%
• Catalyst support loss: < 30%
• PGM Total loading: 0.2 mg/cm2electrode
*based on Pt cost of $450/troy ounce
The main focus of ongoing DOE Fuel Cell Hydrogen Program is fundamentalunderstanding of the oxygen reduction reaction on PtM bimetallic and PtM1M2 (M1=Co,Ni;M2=Fe, Mn, Cr, V, Ti etc) ternary systems that would lead to the development of highly-efficient and durable real-world nanosegregated Pt-skin catalysts with low-Pt content
Objectives-Relevance
ANLTechnical Targets
• Mass activity @ 0.9ViR-free2015 DOE target x 3
• PGM Total content< 0.1g/kW
• Specific activity @ 0.9ViR-free2015 DOE target x 3
• Electrochemical area loss2015 DOE target
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Materials-by-design approach - developed by ANL will be utilized to design,characterize, understand, synthesize/fabricate and test nanosegregated multi-metallicnanoparticles and nanostructured thin metal films
REAL NANOPARTICLESMODEL NANOPARTICLESEXTENDED Multi-M SURFACES
Approach
Nanosegregated Profile
1st Layer
2nd Layer
3rd Layer
4th Layer
Pt=100 at.%
Pt=48 at.%
Ni=52 at.%
Pt=87 at.%
Ni=13 at.%
Pt=75 at.%Ni=25 at.%
Pt[111]-Skin surface
Pt3Ni((111)-Skin is the most active catalyst for the oxygen reduction reaction, and it is ~100 times more active than the state-of-the-art Pt/C catalysts. Design of real-world bi-/multi-metallic catalysts with this activity is our goal.
Well-Defined Systems
d-band center [eV]2.63.03.4
Spec
ific
Act
ivity
: ik @
0.9
V [m
A/c
m2 re
al]
0
1
2
3
4
5
Pt3TiPt3V
Pt3Fe
Pt3CoPt3Ni
Pt-polyPt-skin surfacesPt-skeleton surfaces
Act
ivity
impr
ovem
ent f
acto
r vs
. Pt-p
oly
1
2
3
17
18
19
Target Activity Pt3Ni(111)
(a)
Pt/C ---
Advanced Nanoscale Catalyst
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Approach / Milestone
1.1 Resolved electronic/atomic structure and segregation profile (85%)1.2 Confirmed reaction mechanism of the ORR (95%)
3.3 MEA testing (50 cm2)
2.1 Physical methods: TM films (5-10 layers), nanoparticles (5-300 nm) (90%)2.2 Established chemical methods: colloidal and impregnation synthesis (90%)
1.3 Improved specific and mass activity (95%)
3.1 New PtM1M2 catalyst to increase catalytic activity and decrease dissolution
2.3 Characterization: Ex-situ (UHV, TEM) and in-situ (SXS, EC) (90%)2.4 Theoretical modeling (DFT, MC) methods (90%)
3.2 Carbon support vs. nanostructured thin film catalysts
3.4 Short stack testing verification (>300cm2)
Milestone 1. Fundamental understanding (2009/10) (Accomplished)
Milestone 2. Synthesis and characterization (2009/10)
Future Milestone 3. Fabrication and testing
(Go-No Go Decision Met)
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Relevant Prior Work
V.Stamenkovic, B.Flower, B.S.Mun, G.Wang, P.N.Ross, C.Lucas, N.M.Markovic Science, 315(2007)493
V.Stamenkovic, B.S.Mun, M. Arenz, K.J.J.Mayerhofer, C.Lucas, G.Wang, P.N.Ross, N.M.Markovic Nature Materials, 6(2007)241
V.Stamenkovic, B.S.Mun, K.J.J.Mayrhofer, P.N.Ross, N.M.MarkovicJ. Am.Chem.Soc., 128(2006)8813
V.Stamenkovic, B.S.Mun, K.J.J.Mayrhofer, P.N.Ross,N.M.Markovic, J.Rossmeisl, J.Greeley, J.K. NorskovAngew.Chem.Int.Ed., 45(2006)2897
H.A. Gasteiger, N.M.MarkovicScience, 3124(2009)48
Nanosegregated particle would be the best catalysts for the ORR
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Colloidal deposition approach is used to synthesize (a) monodispersed Pt3Co bimetallic NPs with diameter of 3, 4.5, 6 and 9nm
Technical Accomplishments: Particle Size Effect
Particle size is determined by analyzing TEM images (b-e)
Particle size effect applies to bimetallic NPs
0.1 M HClO4
25 C°
Specific Activity increases withparticle size: 3 < 4.5 < 6 < 9nm
Mass Activity decreases with particle size: optimal size ~5nm
Specific surface area is determined from ΘHupd
0.1 M HClO4
0.1 M HClO4
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As Prepared 400oC
500oC 800oC
Temperature Induced Segregation: apply 400 to 500°C to optimize catalytic activity of the ORR on PtCo bimetallic NPs
MC simulations at 400oC confirmed segregation profile of Pt3Co NPs, which was experimentally observed for extended surfaces
External View Cross Section
Annealing above 500oC provides small increase in specific activity but significant decrease in mass activity of Pt3Co NPs
Technical Accomplishments: Temperature-induced Segregation
TEM: no agglomeration below 500oC
0.1 M HClO4
60C°0.1 M HClO4
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Segregation of Pt at 400oC is not complete in PtxNiy NPs, which induces dissolution of Ni
1 nm
0.22 nm
1 nm1 nm
Pt3Ni PtNi PtNi2 PtNi3
Technical Accomplishments: Composition Effect
Colloidal method is used to synthesize PtxNiy NPs with 3:1, 1:1, 1:2 and 1:3 atomic ratio
~5nm PtxNiyLast step
annealing at 400oC
0.1 M HClO425 C°
0.1 M HClO425 C°
Maximum activity obtained for as-synthetized NPs with 1:1 Pt to Ni atomic ratio
In acidic environment, atomic % of Ni in PtxNiy NPs decreases due to dissolution of Ni surface atoms
Pt3Ni Pt85Ni15 PtNi Pt75Ni25 PtNi2 Pt80Ni20 PtNi3 Pt90Ni10PtNi transforms into Pt3Ni skeleton
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As-prepared PtNi
Inte
nsity
(a. u
.)
Position (nm)43 5210
Position (nm)43 5210
Inte
nsity
(a. u
.)
PtNi
400oC
To be published 2010
Temperature annealing protocol used to transform PtNi1-x skeletons to PtNi/Pt core/shell NPs with 2-3 atomic layers thick Pt shell
PtNi1-y Skeleton
HRTEM characterization
Line profile of NP
Models
Monte CarloSimulations
PtNi/Pt core/shell
Technical Accomplishments: Tailoring of Nanosegregated Layers
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0.01 0.1 1 100.85
0.90
0.95
1.00
6 nm Pt/C acid leached PtNi/C acid leached/annealed PtNi/C
E (V
vs.
RHE
)
jk (mA/cm2)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
PtNi acid leached& annealed
PtNiacid leached
Surfa
ce A
rea
(cm
2 )
Spec
ific
Activ
ity (m
A/cm
2 )
Pt6 nm
0
10
20
30
40
50
x 4
x 7
0.6 0.7 0.8 0.9 1.0
-1.5
-1.0
-0.5
0.0
6 nm Pt/C acid leached PtNi/C acid leached/annealed PtNi/C
I (m
A)
E (V vs. RHE)
Technical Accomplishments: Tailoring the Catalytic Activity
To be published 2010
0.95 V is more accurate to use for ik (mA/cm2)
0.1 M HClO4
25 C°
PtNi/Pt core/shell catalyst has 7 fold improved activity over corresponding (similar size) Pt/C
0.1 M HClO4
25 C°
Activity/Stability trend is controlled by surface coverage of spectator OHad species formed from dissociation of water:
Pt < Pt3Ni (skeleton) < Pt3Ni/Pt core/shell
Pt and PtNi NPs
The same Tafel slope
Multi-layered Pt-shell protects Ni in the core: Pt3Ni/Pt NPs do not suffer from the decay in activity or surface area after 30,000 cycles between 0.5 to 1.1V
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Technical Accomplishments: Catalytic Trends
0.0 0.2 0.4 0.6 0.8 1.0
-1.5
-1.0
-0.5
0.0
Curr
ent (
mA)
E (V vs. RHE)
-0.1
0.0
0.1
Curr
ent (
mA/
cm2 Pt
)
Pt3Fe Pt3Co Pt3Ni
0.1 1 100.85
0.90
0.95
1.00
E (V
vs.
RHE
)
jk (mA/cm2)
0
500
1000
1500
2000
Mas
s Ac
tivity
(A/g
)
Pt3NiPt3CoPt3FePt
0
1
2
3
4
5
Spec
ifc A
ctiv
ity (m
A/cm
2 )
0
20
40
60
80
Spec
ifc S
urfa
ce A
rea
(m2 /g
)
Specific and Mass Activity trends for the ORR of Pt-bimetallic NPs is the same as electrocatalytic trends established on extended Pt3M well-defined surfaces
The same particle size
Pt < Pt3Fe < Pt3Ni < Pt3Co
Similar Hupd coverage
Similar active surface area
The same Tafel slope
ORR Activity Trend
Reaction mechanism for the ORR is the same on extended and real-world nanosegregated Pt3M catalysts; the 4e- serial pathway
Adsorption Trend
The same mechanism
0.1 M HClO4
25C°
0.1 M HClO4
25C°5nm
Activity is determined by electronic properties of the Pt surface atoms, i.e., by surface coverage of blocking non-reactive OHad species - not by the energetics of reaction intermediates
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Technical Accomplishments: Ternary Alloy Catalysts
0
1
2
3
4
5
6
Spec
ifc A
ctiv
ity (m
A/cm
2 )
0
20
40
60
80
100
Spec
ifc S
urfa
ce A
rea
(m2 /g
)
0
500
1000
1500
2000
Mas
s Ac
tivity
(A/g
)
PtFeNiPtCoNiPtFeCoPt0.0 0.2 0.4 0.6 0.8 1.0
-1.5
-1.0
-0.5
0.0
Curr
ent (
mA)
Potential (V vs. RHE)
-0.1
0.0
0.1
PtCoNi PtFeCo PtFeNi
Curr
ent (
mA)
2 4 6 8 100.80
0.85
0.90
0.95
1.00
E (V
vs.
RHE
)
jk (mA/cm2)
Oleylamineoleic acid
~ 200oCTM2+
TM = Fe, Co, and/or Ni
PtM1N2 (NM = Fe, Co, and/or Ni)
To be published 2010
Specific and Mass Activities for ORR of ternary alloys confirmed potential of utilizing TM in further reducing of Pt content
Ternary alloys could provide additional tunability towards activity and stability PtNiCo the most active catalyst
Segregation trends in ternary alloys are still under investigation
Synthesis of
Activity
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Collaborations
• Oak Ridge National Laboratory – HRTEM• Jet Propulsion Laboratory – Alloying and Combinatorial Approach• Brown University – Chemical Synthesis• Indiana University Purdue – Theoretical Modeling• 3M – Testing
PARTNERS
• GM – Collaboration to utilize highly active Pt-alloy catalysts• Argonne National Laboratory – Nanoscale fabrication (CNM)
TECHNOLOGY TRANSFER
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Future Work
• Fundamental understanding of ternary alloy catalysts• Resolving electronic and atomic structures
• Characterization and evaluation of activity and stability trends• Syntheses, characterization and laboratory testing
• Composition screening
FY 2010
FY 2011
• Fabrication and testing in MEA
• Characterization and evaluation of activity and stability trends• Syntheses, characterization and laboratory testing
• Composition validation
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S u m m a r y
1.1 Resolved electronic/atomic structure and segregation profile 1.2 Confirmed the reaction mechanism of the ORR
2.1 Physical methods: TM films (5-10 layers) were used to confirm EC properties2.2 Chemical methods: colloidal solvo-thermal approach in NPs synthesis
1.3 Mass activity and durability improvement are obtained for Pt-alloy NPs
2.5 Novel multimetallic catalyst with Pt increased activity and improved stability
2.3 Characterization: Ex-situ (UHV, TEM) and in-situ (EC, Combinatorial)2.4 Theoretical modeling (DFT, MC) methods
Task 1. Fundamental understanding
Task 2. Synthesis and characterization
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Supplemental Slides
E [V vs. RHE]
0.0 0.2 0.4 0.6 0.8 1.0
Cur
rent
den
sity
[mA
/cm
2 ]
-150
-100
-50
0
50
100
E [V vs. RHE]
0.0 0.2 0.4 0.6 0.8 1.0
Cur
rent
den
sity
[mA
/cm
2 ]
-6
-5
-4
-3
-2
-1
0
1
1 ML Pt on PtNi3 ML Pt on PtNi7 ML Pt on PtNi
Pt Poly
- Pt
1stPt ML2ndPt ML3rdPt ML
- Ni
Thin Film Deposition in UHV
Pt thin film thickness: 1-10 ML
E [V vs. RHE]
0.88 0.90 0.92 0.94 0.96
log
Cur
rent
den
sity
[mA
/cm
2 ]
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Thin Films of Pt over PtNi substrate
0.1 M HClO4
0.1 M HClO4
25 C°
The most active surface is PtNi/Pt-3ML which corresponds to core/shell PtNi/Pt
ORR
Supplemental Slide 1