CO2 and CO Reduction to Liquid Fuel on Oxide-derived Copper

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Christina W. Li GCEP Research Symposium October 15, 2014 CO 2 and CO Reduction to Liquid Fuel on Oxide-derived Copper

Transcript of CO2 and CO Reduction to Liquid Fuel on Oxide-derived Copper

Christina W. Li GCEP Research Symposium

October 15, 2014

CO2 and CO Reduction to Liquid Fuel on Oxide-derived Copper

2 CO2

O2 O2

H2O H2O

renewable energy out

renewable energy in

storage utilization

CO2 Reduction to Liquid Fuels

liquid fuel

renewable energy out

CO, HCOO–

CH3CH2OO– CH3CH2OH

2 CO2

O2 O2

H2O H2O

utilization

CO2 Reduction to Liquid Fuels

CO2 + 2 e– + 2 H+ CO + H2O

2 H2O O2 + 4 e– + 4 H+

cathode

anode

renewable energy in

E (RHE)

–1.0

–0.5

0

0.5

1.0

1.5 O2 + 4 e– + 2 H2O

CO2 + 2 e– + H2O

4 HO–

CO + 2 HO–

1.23

E0 / V

–0.11

2 e– + 2 H2O H2 + 2 HO– 0

min

imum

overpotential (η)

Selectivity: CO vs H2

Activity: current per area vs potential

Stability: activity & selectivity over time

0.01–10 mA/cm2; η = 0.1–1.0 V

% Faradaic efficiency

Key Challenges in CO2 Reduction

Studies on Polycrystalline Cu

Hori, Y. et al. Chem. Lett. 1985, 11, 1695. Hori, Y. et al. J. Chem. Soc. Faraday Trans. I 1989, 85, 2309.

Y. Hori, in Modern Aspects of Electrochemistry, vol. 42, pp. 89-189.

Energetically inefficient

Poor CO2 vs H+ reduction selectivity

Rapid deactivation

Deficiencies:

Synthesis of Oxide-derived Cu

200 nm

After electroreduction Cu annealed at 500 °C for 12 h

2 µm

Oxide-derived Cu (OD-Cu)

CO2 reduction on OD-Cu

Bulk electrolysis: –0.5 V vs RHE in 0.5 M NaHCO3/saturated CO2

Polycrystalline Cu

OD-Cu

3% HCOO–

33% HCOO–

Li, C. W. & Kanan, M. W. J. Am. Chem. Soc. 2012, 134, 7231.

Activity on OD-Cu electrodes

• 0.4–0.5 V less overpotential required for high FE CO2 reduction

• only multi-carbon products observed at high overpotential

polycrystalline Cu Oxide-derived Cu polycrystalline Cu Oxide-derived Cu

C2H4

CH4

C2H4

C2H6

Origin of Enhanced CO2 Reduction

CO Tafel Plot H2 Tafel Plot

• Normalized CO2 reduction activity for OD-Cu and polycrystalline Cu are similar • H2 suppression is responsible for high FE at low ƞ

OD-Cu

Cu NPs

Cu NPs

OD-Cu

500 nm

OD-Cu

400 nm

Cu NPs

–0.5 V, CO2/0.5 M NaHCO3

Comparison to Cu nanoparticles

CO, HCOO–

CH3CH2OO– CH3CH2OH

2 CO2

3 O2 3 O2

3 H2O 3 H2O

renewable energy

solar or wind

energy

storage utilization

CO2 Reduction to Liquid Fuels

Two-step Reduction to Liquid Fuels

Can we access these products with greater efficiency via direct CO reduction? C2H6

CH4

C2H4

E (V vs RHE)

Fara

daic

effi

cien

cy (%

)

C2H4

polycrystalline Cu Oxide-derived Cu

oxygenates oxygenates

ethanol acetate propanol

CO2 + 2 e– + 2 H+ CO + H2O E0 = –0.11 vs RHE

2 CO + 8 e– + 8 H+ CH3CH2OH + H2O E0 = +0.18

CO is the key intermediate for further reduced products

CO Reduction on OD-Cu

Bulk electrolysis: 0.1 M KOH/saturated CO (1 mM)

Li, C. W.; Ciston, J.; Kanan, M. W. Nature 2014, 508, 504.

CO Reduction on OD-Cu

• Both enhancement of CO reduction and suppression of H2 evolution are responsible for high FE at low ƞ

Surface-area normalized CO reduction and H2 evolution

CO reduction pathways: OD-Cu

e–,

e–, H2O HO–

O Tafel kinetics

CO reduction pathways: OD-Cu

HO–

CH3CH2OH 5× e–, H2O

CH3CO2–

e–, H2O

e–,

e–, H2O HO–

O

Structural Characterization of OD-Cu

with Jim Ciston, NCEM

• Grain-boundaries are high-energy bulk defects • Surface energy will depend on misorientation angle

TEM Electron Diffraction: Orientation Mapping

600 nm

600 nm

with Jim Ciston, NCEM and Joe McKeown, LLNL

0 0 1 1 0 1

1 1 1

Misorientation Angle (°)

Num

ber F

ract

ion

MacKenzie Distribution (random texture)

High-density of twin boundaries in OD-Cu

Conclusions and Future Work

• CO2 reduction to liquid fuels is possible via a two-step process.

CO2 + 2 e– + 2 H+ CO + H2O

2 CO + 8 e– + 8 H+ CH3CH2OH + H2O

• Metal-oxide reduction produces unique surfaces for CO2 and CO reduction, which may be correlated to grain-boundary structures.

• Enhanced CO2 and CO reduction faradaic efficiency stems in part from suppression of H2 evolution.

Future Work

• Build structure-activity relationships for grain-boundary density and misorientation angles

• Characterize CO binding strength

• Temperature programmed desorption

• In-situ surface-enhanced Raman spectroscopy

• Synthesize materials with controlled defect and grain-boundary density

• Understanding how defect and grain-boundary structure affect catalytic activity will allow us to better design and optimize catalyts for CO2 and CO reduction

Collaborators: Dr. Jim Ciston (NCEM) Dr. Joe McKeown (LLNL) Dr. Mary Louie (JCAP) Ezra Clark (JCAP) Dr. Badri Shyam (SLAC) Dr. Mike Toney (SLAC)

Acknowledgments

Dr. Yihong Chen Xiaoquan Min Allison Yau Thomas Veltman Dr. Changhoon Lee Dr. Xiaofeng Feng Kennedy McCone George Fei

Professor Matt Kanan

Dr. Craig Gorin Eugene Beh Aanindeeta Banerjee Vivian Lau Graham Dick Dr. Tatsuhiko Yoshino

Surface Enhanced Raman: Preliminary Data

Raman Shift / cm–1

Electrochemically-Deposited Cu

Inactive

OCV

Active

Active

–0.4 V vs. RHE

Cu2O CO

–0.4 V vs. RHE

CO32–

with Mary Louie, JCAP

Activity of OD-Cu 1 and 2

Time / h j /

mA•

cm–2

BE @ –0.5 V vs. RHE 0.5 M NaHCO3

% C

O

Time / h

j / m

A•cm

–2

BE @ –0.5 V vs. RHE 0.5 M NaHCO3

% C

O

OD-Cu 1 OD-Cu 1, 200 °C N2

OD-Cu 2 OD-Cu 2, 200 °C N2

37% HCOO–

6% HCOO–

27% HCOO–

10% HCOO–

E vs RHE (V)

Gold Silver Palladium

% C

O P

rodu

ctio

n

Chen, Y.; Li, C. W.; Kanan, M. W. J. Am. Chem. Soc. 2012, 134, 19969. with Yihong Chen and Xiaoquan Min

Enhanced CO2 Reduction on OD-Metals

Electrodeposition of Nanocrystalline Cu

0.2 M CuSO4, 0.4 M (NH4)2SO4, 0.2 M citric acid Galvanostatic deposition, total charge passed is constant

Size (nm) Strain (%)

6 mA/cm2 31 0.46

12 mA/cm2 23 0.50

24 mA/cm2 19 0.49

6 mA/cm2

12 mA/cm2

24 mA/cm2

500 nm

500 nm

500 nm

Electrodeposition of Nanocrystalline Cu

0.2 M CuSO4, 0.4 M (NH4)2SO4, 0.2 M citric acid Galvanostatic deposition, total charge passed is constant

BE @ –0.5 V vs. RHE 0.5 M NaHCO3

Thermal Stability

Deposition Bath: 0.2 M CuSO4, 0.4 M (NH4)2SO4, 0.2 M citric acid Galvanostatic: 24 mA/cm2, 15 m

No annealing

100 °C, 2 h, 150 sccm N2 200 °C, 2 h, 150 sccm N2

Sample % CO % HCOO– % AcO– %H2

As-dep. 29 35 2 32

100 °C 14 34 4 45

200 °C 0.2 0.8 0.3 99

BE @ –0.5 V vs. RHE 0.5 M NaHCO3

Thermal Stability

Size (nm) Strain (%)

Annealed 200 °C 37 0.42

Annealed 100 °C 23 0.58

ECD 24 mA/cm2 19 0.49

After 12 h BE 28 0.55

ECD 24 mA 100 °C Anneal 200 °C Anneal

500 nm 500 nm 500 nm

Thermal Stability

Deposition Bath: 0.2 M CuSO4, 0.4 M (NH4)2SO4, 0.2 M citric acid Galvanostatic: 24 mA/cm2, 15 m

No annealing

200 °C, 2 h, 100 sccm N2 OD-Cu 1 pc-Cu

Sample % CO % HCOO– % AcO– %H2

As-dep. 29 35 2 32

100 °C 14 34 4 45

200 °C 0.2 0.8 0.3 99

BE @ –0.5 V vs. RHE 0.5 M NaHCO3

Time / h

j / m

A•cm

–2

Nor

mal

ized

j H2 /

mA•

cm–2

Sample RF

As-dep. 104

200 °C 245

OD-Cu 1 160

pc-Cu 1

Cu2O NPs

Cu2O 1

Reduced

Cu2O 2 Cu2O 3

Cu2O NPs

Reduced

2 θ / ° 2 θ / ° 2 θ / °

<D> = 17 nm ԑ = 0.2%

<D> = 29 nm ԑ = 0.4%

<D> = 29 nm ԑ = 0.2%

Cu2O NPs

Time / h

j / m

A•cm

–2

Cu2O NPs 5 mg/cm2, drop-dried onto C-paper

BE @ –0.5 V vs. RHE 0.5 M NaHCO3

Sample % CO % HCOO– % H2

1 16 2 81

2 11 2 86

3 14 3 83

% C

O

Time / h j /

mA•

cm–2

BE @ –0.3 V vs. RHE 0.1 M KOH

Sample % AcO– % EtOH

1 24 28

2 18 22

3 21 24

Cu2O NPs: Other Exps

• Cu2O 1 • Drop-dried onto C-paper • H2 Reduction • Cu2O not fully reduced

• Cu2O NPs • Drop-dried onto C-paper • 1 M KOH

Red T Qred jtot % AcO– % EtOH jCO

80 °C 5.0 2.6 19 34 1.4

100 °C 2.2 2.1 19 40 1.3

E v. RHE jtot % AcO– % EtOH jCO

–0.2 0.62 64 13 0.48

–0.25 1.4 14 16 0.43

TEM Precessional Electron Diffraction

1 µm 1 µm

with Jim Ciston and Joe McKeown, LLNL

CO reduction pathways: Cu(100) DFT studies

Calle-Vallejo, F.; Koper, M. T. M. Angew. Chem. Int. Ed. 2013, 52, 7282.

e–,

Ethylene favored over ethanol by 0.2 eV

No ethanol observed experimentally by DEMS

CO reduction pathways: OD-Cu

Li and Kanan 2013 submitted

Tafel kinetics Selectivity in 1 M KOH

0.1 M KOH 1 mM CO

HO– e–,

Tuning OD-Cu catalytic properties

500 °C in air

OD-Cu 1 (electroreduced)

–0.5 V

Cu2O/Cu electrode 500 nm

OD-Cu 1

OD-Cu 2 (H2- reduced)

H2, 130 °C

Cu2O/Cu electrode 500 nm

OD-Cu 2

500 °C in air

400 nm

Cu NP powder

Cu NP powder electrode

glass slide

drop cast

Cu NPs

Tuning OD-Cu catalytic properties

500 nm

OD-Cu 1

500 nm

OD-Cu 2

400 nm

Cu NP powder

OD-Cu 1

Cu NP powder

GIXRD

OD-Cu 2

<D> microstrain

0.01%

0.2%

40 nm

30 nm

<0.1% 50 nm

Comparison between OD-Cu 1 & OD-Cu 2

Geometric CO reduction activity

Li and Kanan 2013 submitted

conditions: 0.1 M KOH, 1 mM CO

OD-Cu 1

Cu NP powder

OD-Cu 2

Comparison between OD-Cu 1 & OD-Cu 2

Normalized CO reduction activity

Li and Kanan 2013 submitted

conditions: 0.1 M KOH, 1 mM CO

OD-Cu 1

Cu NP powder

OD-Cu 2

22× 45×

Normalized H2O reduction activity

Cu NP powder

OD-Cu 2

OD-Cu 1

Tuning OD-Cu catalytic properties

3 CO + 12 e– + 10 H2O CH3CH2CH2OH + 12 HO–

0.1 M KOH, 1 mM CO n-PrOH

Acknowledgments

Matt Kanan Yihong Chen Kanan Group

E (RHE) en

ergy

sto

red

–1.0

–0.5

0

0.5

1.0

1.5 O2 + 4 e– + 4 H+

CO2 + 4 e– + 4 H+

CO2 + 2 e– + 2 H+

CO2 + 2 e– + 2 H+

CO2 + 6 e– + 6 H+

CO2 + 8 e– + 8 H+

2 e– + 2 H+

2 H2O

CH4 + 2 H2O

CH3OH + H2O

CH2O + H2O

CO + H2O

HCO2H + H2O

H2

η

1.23

E0 / V

0.17

0.03

0

–0.07

–0.11

–0.20

Equilibrium Potentials for CO2 Reduction

Studies on Single-Crystal Cu

Hori, Y. et al. J. Mol. Cat. A 2003, 199, 39. Hori, Y. et al. J. Electroanal. Chem. 2002, 533, 135.

Norskov, J. et al. Surf. Sci. 2011, 605, 1354.

Bragg’s Law

n λ = 2 d sin θ

Real Surface Area

Q = CE dQ/dt = C * dE/dt I = C * (scan rate) C = (εε0/L) * A

Waszczuk, P. et al. Electrochimica Acta 1995, 40, 1717

Annealed Cu: 13.9 mF Cu: 29.3 μF Roughness factor = 476

Characterization of annealed Cu

After electroreduction Cu annealed at 500 °C for 12 h

Characterization of annealed Cu

After electroreduction Cu Annealed at 700 °C for 1 h

2 µm 1 µm 1 µm 300 nm

Electrode post-processing

• Electrode annealed at 500 °C for 1 h • Reduced at–0.5 V vs. RHE overnight • Annealed at 160 °C under vacuum for 2 h • Bulk electrolysis: – 0.5 V vs. RHE in 0.5 M NaHCO3 /sat. CO2

Annealed at 500 °C for 1h After vacuum annealing

Galvanostatic Oxide Reduction

• Electrodes annealed at 500 °C for 1 h • Reduced at indicated current density until plateau potential is

reached • Bulk electrolysis: –0.5 V vs RHE in 0.5 M NaHCO3/saturated CO2

100 µA/cm2

1 mA/cm2

10 mA/cm2

20 mA/cm2

50 mA/cm2

Electrolyte Screen

Electrolyte (0.5 M) Initial pH % CO % HCOOH % H2 jtot jCO2

NaHCO3 7.2 37.2 32.8 10.7 2.02 1.42

KHCO3 7.4 28.9 35.5 18.0 2.63 1.70

LiHCO3 7.3 25.8 35.0 18.9 2.30 1.40

LiClO4 3.7 29.8 39.0 10.5 1.75 1.20

NaClO4 3.4 26.4 29.9 18.0 1.26 0.71

KCl 4.2 26.4 10.1 33.7 1.22 0.44

LiCl 3.9 31.8 15.2 18.0 0.73 0.34

Na2SO4 4.2 11.5 23.6 37.8 1.69 0.59

NaOAc 6.1 3.8 3.0 61.0 1.70 0.12

NaH2PO4 4.2 0.18 0 70.5 5.94 0.011

• All electrodes annealed at 500 °C for 1 h • –1.13 V vs Ag/AgCl (variable E vs RHE depending on pH)

Chemical Oxidation of Cu

Conditions: 1) 0.05 M (NH4)2S2O8, 1.25 M NaOH 2) 0.1 M (NH4)2S2O8, 2.5 M NaOH 3) 0.2 M (NH4)2S2O8, 5 M NaOH

Soaked Cu foil for 3 hours Rinsed with IPA and diH2O

Crystalline CuO and Cu(OH)2

Zhang, W. et al. Inorg. Chem. 2003, 42, 5005.

3

Chemical Oxidation of Cu j to

t / m

A•cm

-2

CO E

ffici

ency

/ %

Time / h Time / h

1 2 3

Q•cm-2 (C) % CO % HCO2H 1 1.06 13.5 9 2 3.24 19.7 21 3 3.37 32.6 26

Bulk electrolysis: –0.5 V vs RHE in 0.5 M NaHCO3/saturated CO2

500 nm

3