Past, Present, and Future Challenges in Electrocatalysis for Fuel Cells [PDF]

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FCTO Monthly Webinar Series: Past, Present and Future Challenges in Electrocatalysis for Fuel Cells

Presenter: Voya (Vojislav) Stamenkovic Argonne National Laboratory 1 | Fuel Cell Technologies Office

DOE Host: Dimitrios Papageorgopoulos Fuel Cell Technologies Office

U.S. Department of Energy Fuel Cell Technologies Office October 13th, 2016 eere.energy.gov

Question and Answer • Please type your questions into the question box

2 2 | Fuel Cell Technologies Office

eere.energy.gov

Past, Present and Future Challenges in Electrocatalysis for Fuel Cells Materials Science Division A r g o n n e N a t i o n a l Laboratory Vojislav Stamenkovic

DOE EERE Fuel Cell Technology Office Webinar Series October 13, 2016

https://www.toyota.com/mirai/fcv

2016 Toyota Mirai $499/month 36-month lease $57,500 MSRP

HYDROGEN SAFETY Science behind the safety Safety was our primary objective when we engineered the Mirai. Our proprietary safety system is based on four fundamental principles.

The first production fuel cell vehicle The Mirai is at the forefront of a new age of hydrogen fuel cell cars that allows you to enjoy long distance zero-emissions driving. As well as only producing water from its tailpipe – which means no impact on our planet when you're driving – Mirai brings the unique Toyota Hybrid driving experience to a new level.

’60s PEM FC unsupported Pt catalyst loading: 28 mgPt/cm2 membrane: Nafion T ~ 21oC

’60-70s Alkaline FC Ni based catalyst T ~ 250oC Operating time: 400-690h

’80-2011 Alkaline FC Pt and PtAu catalysts loading: 10 and 20 mgPt/cm2 T ~ 93oC Operating time: > 16 days

Particle Size Effect 10 % Pt/Vulcan 3 nm

30 nm (Pt/C)

 cubo-octahedral

particles

5

ORR: cathode limitations 2020 DOE Technical Targets • Mass activity @0.9V: 0.44 A/mgPt

losses ~ 30-40% (!!!)

Cathode kinetics (?!)

• Electrochemical area loss: < 40% • PGM Total content: 0.125 g/kW • PGM Total loading: 0.125 mg/cm2electrode • Durability w/cycling (80oC): 5000 hrs

Main limitations in PEM fuel cell technology: 1) Activity: Pt/C = Pt-poly/10 2) Durability: (Pt catalyst dissolves) 3) Pt loading: Cost Issues 7

Activity | Durability | Cost Specific/Mass Activity

Electrochemical Stability

Loading

1o Structure-Function 2o Composition-Function 3o Surface Modifications 4o Tailored Electrolytes

STM: Pt Single Crystals As prepared

Pt(111)

(b)

(c)

Current Density (a. u.)

(a)

Pt(100) 12.0

Pt(110)

Kinetic Current Density [mA/cm^2]

As prepared

10.0

8.0

Pt(110) Pt(111) Pt(100) Series4 Pt-poly average

6.0

4.0

2.0

0.0

0.925 V

0.900 V

0.875 V

0.850 V

9

In-Situ EC-ICP-MS

Pt(hkl)-Surfaces vs. Pt/C Quadrupole mass filter

Electrochemical Cell

Horizontal torch

Total Pt loss over one potential cycle up to 1.05 V for distinct Pt surface morphologies, indicating the stability trend follows the coordination number of the surface sites

Pt Surface

Dissolved Pt per cycle [µML]

Pt(111)

2

Pt(100)

7

Pt(110)

83

Pt-poly

36

Pt/C

| 103*

P. P. Lopes, D. Strmcnik, J. Connell, V. R. Stamenkovic and N.M. Markovic

ACS Catalysis, 6 (4), 2536-2544, 2016

10

Surface Structure + Composition: Pt3Ni[hkl] Surfaces LEED

STM

(d)

Pt3Ni(111)

LEIS

p(1x1)

(e)

[01

-1 ]

[0 11 ]

Sputtered

Pt3Ni(100)

c(5x1)

(f)

Pt3Ni(110)

Annealed

[1-10]

[001]

(110)-(1x1)

11

Activity: ORR Platinum Alloy Surfaces Pt(hkl)

Pt3Ni(hkl) Pt3Ni(hkl)

0.1 M HClO4

0.1 M HClO4 0.95 V vs. RHE 20 °C

Pt3Ni(hkl) Pt (111) (100) (110) (111)

Science, 315 (2007) 493

Pt3Ni(110)

Pt3Ni(100)

Pt3Ni(111)

Pt3Ni(111)/Pt-Skin Surface is the most active catalyst for the ORR 12

Subsurface Composition + Surface Structure: Pt3Ni(111) 0.6 0.8 1.0

E [V] vs. RHE 0.2

0.4

(a)

7.0

6.0

(a’)

80

20

60

40

40

60

20

80

1

60

SXS

100

0 2

3

4

5

y Atomic layer

6

(b)

7

Pt3Ni(111)

2

i [µA/cm ]

0

Ni [at. %]

6.5

%]

100

Pt [at. Pt %] [at.

Intensity [arb. units]

0.0

30 0

Pt(111)

-30

CV

2

i [mA/cm ]

H2O2 [%]

60

(c)

60

30

30

0

0

50 0

ΘOxd [%]

ΘHupd [%]

-60

(d)

-2

∆E~100 mV

-4

ORR

Pt poly

-6

II

I 0.0

0.2

0.4

III 0.6

E [V] vs. RHE

0.8

1.0

Science, 315(2007)493

Pt3Ni(111)/Pt-Skin Surface is the most active catalyst for the ORR (100-fold enhancement) 13

Subsurface Composition + Surface Structure: Pt3Ni(111) 0.6 0.8 1.0

E [V] vs. RHE 0.2

0.4

(a)

7.0

6.0

(a’)

80

20

60

40

40

60

20

80

1

60

SXS

100

0 2

3

4

5

y Atomic layer

6

(b)

7

Pt3Ni(111)

2

i [µA/cm ]

0

Ni [at. %]

6.5

%]

100

Pt [at. Pt %] [at.

Intensity [arb. units]

0.0

30 0

Pt(111)

-30

CV

2

i [mA/cm ]

H2O2 [%]

60

(c)

60

30

30

0

0

50 0

ΘOxd [%]

ΘHupd [%]

-60

(d)

-2

∆E~100 mV

-4

ORR

Pt poly

-6

II

I 0.0

0.2

0.4

III 0.6

E [V] vs. RHE

0.8

1.0

Science, 315(2007)493

Pt3Ni(111)/Pt-Skin Surface is the most active catalyst for the ORR (100-fold enhancement) 13

Controlled Synthesis: Multimetallic Nanocatalysts Colloidal solvo - thermal approach has been developed for monodispersed PtM NPs with controlled size and composition

Efficient surfactant removal method does not change the catalyst properties

PtMControlled Alloy NPsSynthesis: | Distribution: Elements and Particle Size Multimetallic Nanocatalysts HAADF - STEMhas solvo - thermal approach

Colloidal been developed for monodispersed PtM NPs with controlled size and composition

1o Particle size effect applies to Pt-bimetallic NPs Specific Activity increases with particle size: 3 < 4.5 < 6 < 9nm

Mass Activity decreases with particle size

Particle size distribution

Optimal size particle size ~5nm J. Phys. Chem. C., 113(2009)19365 100

davg = 5.9segregation nm 2o Temperature induced in Pt-bimetallic NPs Agglomeration prevented 80

Counts

(b)

60

Optimized annealing temperature 400-500oC Phys.Chem.Chem.Phys., 12(2010)6933 40

3o Composition effect in Pt-bimetallic NPs Pt3M

20

PtM2

PtM

PtM3

0.22 nm

1 nm

0

1 nm

1 nm

1 2 of 3 Pt-bimetallic 4 5 6 NPs7 is PtM 8 9 Optimal composition

10

Adv. Funct. Mat., 21(2011)147 Size (nm)

4o Surface chemistry of homogeneous Pt-bimetallic NPs PtxM(1-x) NPs

Efficient surfactant removal method does not change the catalyst properties

ACS Catalysis, 1 (2011) 1355

Dissolution of non Pt atoms forms Pt-skeleton surface

14

Controlled Synthesis: Multimetallic Nanocatalysts Colloidal solvo - thermal approach has been developed for monodispersed PtM NPs with controlled size and composition

1o Particle size effect applies to Pt-bimetallic NPs Specific Activity increases with particle size: 3 < 4.5 < 6 < 9nm

Mass Activity decreases with particle size Optimal size particle size ~5nm J. Phys. Chem. C., 113(2009)19365

2o Temperature induced segregation in Pt-bimetallic NPs Agglomeration prevented (b)

Optimized annealing temperature 400-500oC Phys.Chem.Chem.Phys., 12(2010)6933

3o Composition effect in Pt-bimetallic NPs Pt3M

PtM2

PtM

PtM3

0.22 nm

1 nm

1 nm

1 nm

Optimal composition of Pt-bimetallic NPs is PtM Adv. Funct. Mat., 21(2011)147

4o Surface chemistry of homogeneous Pt-bimetallic NPs PtxM(1-x) NPs

Efficient surfactant removal method does not change the catalyst properties

Dissolution of non Pt atoms forms Pt-skeleton surface

PtxNi1-x: Surface Chemistry and Composition Effect

Adv. Funct. Mat., 21 (2011) 14715

15

PtxNi1-x: Surface Chemistry and Composition Effect

Adv. Funct. Mat., 21 (2011) 14715

15

PtNi with multilayered Pt-Skin Surfaces : Tailoring Nanoscale Surfaces Temperature annealing protocol used to transform PtNi1-x skeletons to multilayered PtNi/Pt NPs with 2-3 atomic layers thick Pt-Skin PtNi/Pt core/shell As-prepared PtNi PtNi1-y Skeleton

400oC

HRTEM

Intensity (a. u.)

Line profile

Intensity (a. u.)

Pt Ni

0

1

2

3

Position (nm)

4

5

0

1

2

3

Position (nm)

4

5

16

NPs with multilayered Pt-Skin Surface: PtNi/C Leached

As Synthesized

Annealed

Multilayered Pt-skin NP



TEM

Catalysts with multilayered Pt-skin surfaces exhibit substantially lower coverage by Hupd vs. Pt/C (up to 40% lower Hupd region is obtained on Pt-Skin catalyst)

Pt-NPs

Surface coverage of adsorbed CO is not affected on Pt-skin surfaces

PtNi-NPs

davg = 5 nm

Ratio between QCO/QHupd>1 is indication of Pt-skin formation Catalyst Pt/C PtNi/C PtNi-skin/C

QH (µC) 279 292 210

ECSAH (cm2) 1.47 1.54 1.10

QCO (µC) 545 615 595

ECSACO (cm2) 1.41 1.60 1.54

QCO/2QH 0.98 1.05 1.42

Electrooxidation of adsorbed CO (CO stripping) has to be performed for Pt-alloy catalysts in order to avoid underestimation electrochemically active surface area and overestimation of specific and mass activities

17

PtNi Catalyst: RDE Studies of Multilayered Pt-Skin Surfaces

0.0 8340

8360

E (eV)

8380

0.5

acid treated acid treated/annealed Pt

0.0 11540

11560

11580

E (eV)

11600

11620

1.0

-0.1 1.00

d 2 ) i (mA/cmgeo

1.0

0.8

0.0

8400

Pt L3 at 1.0 V

0.6

0

-2

e

0.95

0.90

0.1

1 2

jk (mA/cm )

-4

1.0

before 0.8

after

6

0.6

8

6

4

0.4

4

2

0.2 0.0

10

Improvement Factor (vs. Pt/C)

acid treated acid treated/annealed Ni NiO

0.4

6 nm Pt/C acid treated PtNi/C acid treated/annealed PtNi/C

E (V vs. RHE)

0.5

1.5

Normalized Absorption µ(E)

0.2

0.1

1.0

8320

b

0.0

Specific Activity (mA/cm2)

Ni K at 1.0 V

1.5

E (V vs. RHE)

c

i (mA/cm2Pt)

Normalized Absorption µ(E)

a

Pt/C

PtNi/C Skeleton

before

PtNi/C Skin

0

2

0

after

-6 0.6

0.7

0.8

0.9

1.0

E (V vs. RHE)

TEM/XRD: Content of Ni is maximized and allows formation of the multilayered Pt-skin by leaching/annealing RDE: PtNi-Skin catalyst exhibits superior catalytic performance for the ORR and is highly durable system In-Situ XANES: Subsurface Ni is well protected by less oxophilic multilayered Pt-skin during potential cycling Durability: Surface area loss about 10%, SA 8 fold increase and MA 10 fold increase over Pt/C after 20K cycles

J. Amer. Chem. Soc. 133 (2011) 14396

18

Mass Activity Enhancement by 3D Surfaces: Multimetallic Nanoframes In collaboration with Peidong Yang, UC Berkeley

- H2PtCl6 and Ni(NO3)2 react in oleylamine at 270oC for 3 min forming solid PtNi3 polyhedral NPs - Reacting solution is exposed to O2 that induces spontaneous corrosion of Ni - Ni rich NPs are converted into Pt3Ni nanoframes with Pt-skeleton type of surfaces - Controlled annealing induces Pt-Skin formation on nanoframe surfaces

Science , 343 (2014) 1339

20

Compositional Profile: PtNi Nanoframes with Pt-skin Surfaces

- Narrow particle size distribution - Hollow interior - Formation of Pt-skin with the thickness of 2ML - Surfaces with 3D accessibility for reactants - Segregated compositional profile with overall Pt3Ni composition Science , 343 (2014) 1339

21

Multimetallic Nanoframes with 3D Electrocatalytic Surfaces

Science , 343 (2014) 1339

22

Improving the ORR Rate by Protic Ionic Liquids [MTBD][beti]

Chemically Tailored Interface High O2 solubility along with hydrophobicity yield improved ORR kinetics

CO2 ,[MTBD][beti ] = 2.40 ± 0.013 CO2 ,HClO4

0.95 V vs. RHE

Pt/C

Erlebacher and Snyder, Advanced Functional Materials, 23(2013)5494

np-NiPt/C

np-NiPt/C+IL

23

Tailoring Activity: PtNi Nanoframes as the ORR Electrocatalyst

RDE @ 0.95V vs. RHE 0.1M HClO4 1600 rpm

- No change in activity after 10K cycles 0.6 – 1.0 V - Specific activity increase over 20-fold vs. Pt/C

C

RDE @ 0.90V vs. RHE 0.1M HClO4 1600 rpm

- Mass activity increase over 35-fold vs. Pt/C - Increase in mass activity over 15-fold vs. DOE target

Science , 343 (2014) 1339

24

DURABILITY: Pt/C

Initial morphology

After 60,000 cycles Potential Range: 0.6-1.0V

25

Commercial Pt/C Catalysts

c

d



Commercial catalysts are usually made by impregnation methods.



Poor control – Broad size distribution – Different, undefined morphologies, but everyone calls them “cubo-octahedral”, which is, in fact, not correct!

e

26

DURABILITY: Pt/C

Initial morphology

Potential Range: 0.6-1.0V

After 60,000 cycles

27

DURABILITY: Pt/C

Initial morphology

Potential Range: 0.6-1.0V

After 60,000 cycles

27

SIZE EFFECT(s)? Pt/C

28

SHAPE EFFECT(s)? Pt/C

20 nm

cubo-octahedron

truncated cube

cube

• Uniform morphology • Size control octahedron (?)  cubo-octahedral  Cube 29

HR-TEM: Characterization of Nanoscale Pt/C Catalyst 1) Shape: cubooctahedron 2) Size distribution: 2-15 nm 3) Composition: Pt, C

x 15

4) Side Orientation: [111], [100]

x5

3 nm

30

APPROACH: Well-Defined Systems (ext & nano) (111) (100) [001]

Kinetic Current Density [mA/cm^2]

12.0

0.08 0.06

8.0

6.0

4.0

2.0

2.0x10-4

0.0

0.04

0.925 V

0.900 V

0.875 V

0.850 V

0.02 0.00

I/A

i [mA/cm2]

10.0

Pt(110) Pt(111) Pt(100) Series4 Pt-poly average

0.0

-0.02 -0.04 -0.06

-2.0x10-4

-0.08 0.0

0.2

0.4

0.6

E [V vs RHE]

0.8

1.0

0.0

0.2

0.4

0.6

E/V vs. RHE

31

ICP-MS: Principle of Operation Quadrupole mass filter

Horizontal torch

Quadrupole

Quadrupole allows single m/z pass at any given time Time frame for the range of m/z = 1 – 240 is 0.1sec

Detector

32

RDE/ICP-MS: Pt(hkl)

Rotating Disk Electrode 333

In-Situ RDE / ICP-MS: Standard Deviation

Pt(hkl)-Surfaces vs. Pt/C Total Pt loss over one potential cycle up to 1.05 V for distinct Pt surface morphologies, indicating the stability trend follows the coordination number of the surface sites

σ=(Σ(µ-xi)2/n-1)1/2 DL=3σbckg(λ)

Pt Surface

Background

λ (amu)

Dissolved Pt per cycle [µML]

Pt(111)

2

Pt(100)

7

Pt(110)

83

Pt-poly

36

Pt/C

| 103*

 Method detection limit (DL) is applied to blank sample prepared with all analytical steps related to given methodology, since each step is potential error source  Limit of quantification (LOQ) is 3 times DL

34

In-Situ RDE / ICP-MS:

Pt/C, Pt and Pt/Au Well-Defined Surfaces

GC-Au-Pt(4ML)

GC-Pt(4ML)

Pt/C

| 103*

35

DURABLE NPs: Core-Interlayer-Shell Particles 0.2 A

0.4

0.6

I

II

E (V vs RHE) 0.8

1.0

1.2

1.4

III

1.6

1.8

IV

40 x3

I (µA cm-2)

0 -40

I would love double this area to blank out H Au-OH Pt-OH layer I would love this area to blank out 3 -80 love this area to blank out Au(111) 2I would Au(111)-Pt 1I would loveNiPt this area to blank out 8 ORR @ 0.9V Au(111)-FePt

i (mA cm )

-2

-2 -3 -4 -5 -6 0.2

0.4

0.6

0.8

1.0

E (V vs RHE)

C 3

6 2 4 2 0

Pt -p Au oly (1 11 Fe )-Pt P Au 3t -p o (1 11 ly )-F eP t 3

33

B 0 -1

0.0

ad

ad

1

Improvement Factor vs Pt Poly

upd

Specific Activity (ikin / mA cm-2)

4

I want 1.4 this blanked 1.2 1.6 out! 1.8

Nano Letters, 11 (2011) 919

36

DURABLE NPs: Core-Interlayer-Shell Particles 0.2 A

0.4

0.6

I

II

E (V vs RHE) 0.8

1.0

1.2

1.4

III

1.6

1.8

IV

40 x3

I (µA cm-2)

0 -40

I would love double this area to blank out H Au-OH Pt-OH layer I would love this area to blank out 3 -80 love this area to blank out Au(111) 2I would Au(111)-Pt 1I would loveNiPt this area to blank out 8 ORR @ 0.9V Au(111)-FePt

i (mA cm )

-2

-2 -3 -4 -5 -6 0.2

0.4

0.6

0.8

1.0

E (V vs RHE)

C 3

6 2 4 2 0

Pt -p Au oly (1 11 Fe )-Pt P Au 3t -p o (1 11 ly )-F eP t 3

33

B 0 -1

0.0

ad

ad

1

Improvement Factor vs Pt Poly

upd

Specific Activity (ikin / mA cm-2)

4

I want 1.4 this blanked 1.2 1.6 out! 1.8

Nano Letters, 11 (2011) 919

36

Compositional Profile: Core/Interlayer/Shell Electrocatalysts Au interlayer Ni core

2 nm

2 nm

4nm

PtNi shell

~ 5-6nm

Monodisperse , Core/Interlayer/Shell NPs: Ni core / Au interlayer / PtNi shell

37

Durable ORR Catalysts: Core/Shell NPs with Au Interlayer Stabilization mechanism

- Pt

- Au

- Ni - Fe

-O

segregation trend of Pt into the bulk segregation trend of Au onto surface driving force that diffuses Pt into the bulk driving force induced by strong Pt - OHad interaction

Nano Letters, 14 (2014) 6361

38

Durable Systems: PtNi Nanoframes in MEA in collaboration with Debbie Myers, ANL - CSE

Nanoframes in 5cm2 MEA ANL and ORNL

Cathode Loading: 0.035 mg-Pt/cm2, I/C = 0.8 H2/O2, 80°C, 150 kPa(abs), 100%RH ORR Activity @ 0.9V: Mass Activity x3.5 Specific Activity x6.5 TKK 20 wt%Pt/C: 0.22 A/mg-Pt 0.39 mA/cm2-Pt PtNi Nanoframes: 0.76 A/mg-Pt 2.60 mA/cm2-Pt

39

Durable Systems: PtNi Nanoframes (before and after) Nanoframes in 5cm2 MEA ANL and ORNL BF-STEM

catalyst layer

HAADF-STEM

0.1 µm

membrane

0.1 µm

BF-STEM

5 nm

membrane Pt Ni

5 nm

40

Durable Systems: PtNi with Multilayered Pt-Skin Surfaces 1.00

IR corrected Cell Voltage (V)

0.95

Commercial TKK Pt/C PtNi/C

0.90 0.85

H2/O2 Performance

0.80 0.75 0.70 0.65 0.60 0.55 0.50

0

500

1000

1500

2000

2500

3000

Cell Voltage without IR compensation (V)

in collaboration with Debbie Myers, ANL - CSE 1.0 Commercial TKK Pt/C PtNi/C

0.8

H2/Air Performance 0.6

0.4

0.2

0

TKK 20 wt%Pt/C PtNi 16.7 wt%Pt/C

600

900

1200

PtNi

TKK Pt

Pt loading

mgPGM/cm²geo

0.045

0.045

Mass Activity (H2-O2)

A/mgPGM @ 0.9 ViR-free

0.60

0.27

Specific Activity (H2-O2)

mA/cm2PGM @ 0.9 ViR-free

1.85

0.39

mA/cm2 @ 0.8 V

101

47

m2/gPGM

35.10

52.5

ECSA

1800

Current Density (mA/cm )

Units

MEA performance (H2-Air)

1500 2

Current Density (mA/cm2)

Cathode Loading: 0.046 mg-Pt/cm2 I/C = 1, H2/O2 (or Air), 80°C, 150 kPa(abs), 100%RH

300

41

TM doped Pt3Ni Octahedra

SA and MA over 70-fold vs. Pt/C

Huang et al. Science , 348 (2015) 1230

Hierachical PtCo Nanowires

SA and MA over 30-fold vs. Pt/C

Bu et al. Nat. Commun. , (2016) DOI 10.1038.natcomms11850

Dealloying of PtNi octahedrons

SA and MA over 10-fold vs. Pt/C

Cui et al. Nature Mat., 12 (2013) 765

Alloying Pt with Rare Earth Elements

SA over 6-fold vs. Pt/C Greeley et al. Nature Chem., 1 (2009) 552

Escudero-Escribano et al. Science, 352 (2013) 73

Pt/CuNW and PtNT

Pt/CuNW

PtNT

SA and MA over 3-fold vs. Pt/C

Alia et al. ACS Catalysis., 3 (2013) 358

BNL: Electrocatalyst Development

Remaining Challenges and Barriers

1) Durability of fuel cell stack (

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