solid oxide electrolysis cells: long-term...

Solid Oxide Electrolysis Cells: Long-term Durability Steam electrolysis Carbon dioxide electrolysis Co-electrolysis of steam and carbon dioxide

Sune D Ebbesen,

Christopher Graves, Anne Hauch, Søren H Jensen, Ruth Knibbe, and Mogens Mogensen

Fuel Cells and Solid State Chemistry Division, Risø National Laboratory for Sustainable Energy,

The Technical University of Denmark

Outline

•Risø Ni/YSZ based Solid Oxide Cells

•Performance of Risø Ni/YSZ based Solid Oxide Cells

•Setup for testing Solid Oxide Cells at Risø

• Influence if impurities

•Electrolysis durability at low current density — Steam — Carbon dioxide — Carbon dioxide + steam

•Electrolysis durability at high current density — Steam, Carbon dioxide or Carbon dioxide + steam

•Summary

Risø Ni/YSZ based Solid Oxide Cells

Support layer: Ni/YSZ

Fuel electrode: Ni/YSZElectrolyte: YSZOxygen electrode: LSM

• Steam electrolysis

• Carbon dioxide electrolysis

→2 2CO CO + ½ O

→2 2 2H O H + ½ O






• Water Gas Shift (WGS) / Reverse Water Gas Shift (RWGS)

2 2 2H O + CO H + CO

→2 2CO CO + ½ O

→2 2 2H O H + ½ O




Performance of Risø Ni/YSZ based Solid Oxide Cells

0.5

0.7

0.9

1.1

1.3

1.5

-1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6

i / A.cm-2

Cel

l vol

tage

/ V

50% H2O – 25% H2 – 25% Ar

H2 O/H2 : ASRelectrolysis = 0.24 Ωcm2 ASRfuel cell = 0.25 Ωcm2

— 850ºC Performance of Risø Ni/YSZ based Solid Oxide Cells

0.5

0.7

0.9

1.1

1.3

1.5

-1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6

i / A.cm-2

Cel

l vol

tage

/ V

50% H2O – 25% H2 – 25% Ar25% CO2 – 25% H2O – 25% CO – 25% Ar50% CO2 – 25% CO – 25% Ar


CO2 /CO: ASRelectrolysis = 0.34 Ωcm2 ASRfuel cell = 0.32 Ωcm2




H2 O/CO2 /CO: ASRelectrolysis = 0.28 Ω

cm2 ASRfuel cell = 0.27 Ωcm2

0.5

0.7

0.9

1.1

1.3

1.5

-1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6

i / A.cm-2

Cel

l vol

tage

/ V

50% H2O – 25% H2 – 25% Ar25% CO2 – 25% H2O – 25% CO – 25% Ar50% CO2 – 25% CO – 25% Ar


0.5

0.7

0.9

1.1

1.3

1.5

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6

i / A.cm-2

Cel

l vol

tage

/ V

50% CO2 – 25% CO – 25% Ar50% CO2 – 25% H2 – 25% Ar

CO2 /H2 : ASRelectrolysis = 0.28 Ωcm2 ASRfuel cell = 0.27 Ωcm2



Electrolysis in Solid Oxide Cells



• Co-electrolysis of carbon dioxide and steam

2 2CO CO + O→

2 2 2H O H + O→

→2 2 2 2

2 2 2

CO + H O CO + H + O

H O + CO H + CO

Setup for testing Solid Oxide Cells at Risø

Cell holder,Bottom piece

O2/Air flow

Ni foilcurrent collector

Ni Mesh

Cell holder,Top piece

Pt foilcurrent collector

Cell

H2O/H2CO2/CO

Flow

Pt Mesh

Voltage probes(In-plane)

0.00.20.40.60.81.01.21.41.6

0 5 10 15 20 25 30 3500.20.40.60.811.21.41.61.8

Inpl

ane

volta

ge

Cor

rosp

ondi

ng c

ell v

olta

ge

Time

Inplane voltage

Cell voltage

Setup for testing Solid Oxide Cells In-plane explanation

Inlet Outlet

Durability of Ni/YSZ supported Solid Oxide Cells



• Low current density degradation (~ upto -1 A/cm2 at 850ºC)

• High current density degradation (~ above -1 A/cm2 at 850ºC)

Electrolysis durability at low current density — Steam


1.10

1.15

1.20

1.25

1.30

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400Time (h)

Cell

volta

ge (V

) Passivation Activation Long term degradation

850ºC, -0.50 A/cm2, 50% H2 O / 50% H2



1.10

1.15

1.20

1.25

1.30

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400Time (h)

Cell

volta

ge (V

) Passivation Activation Long term degradation

-0.25

0.00

0.25

0.50

0.75

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400

Time (h)

In-p

lane

vol

tage

(mV

)

850ºC, -0.50 A/cm2, 50% H2 O / 50% H2



850ºC, -0.50 A/cm2, 50% H2 O / 50% H2

-0.20

-0.15

-0.10

-0.05

0.00

0.050 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Z' (Ω ·cm2)

Z'' (Ω

·cm

2 )

12 Hz1.2 Hz

120 Hz

1.2 kHz

1.2 kHz

0 h260 h1315 h

0

10

2030

40

50

6070

80

90

1 10 100 1000 10000 100000Frequence (Hz)

Δt ∂

Z'(f)

/ ∂l

n(f)

( Ω·c

m2 )

t = 260 h

TimeMaximal degradation: 115 mV

-0.20

-0.15

-0.10

-0.05

0.00

0.050 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Z' (Ω ·cm2)

Z'' (Ω

·cm

2 )

12 Hz1.2 Hz

120 Hz

1.2 kHz

1.2 kHz

0 h260 h1315 h



850ºC, -0.50 A/cm2, 50% H2 O / 50% H2

→

4 2 2

(gas) (ads)

Electrolysis:Si(OH) SiO + H O

Impurities Impurities

Electrolysis durability at low current density — Carbon dioxide


850ºC, -0.25 A/cm2, 70% CO2 / 30% CO

1000

1050

1100

1150

1200

1250

0 100 200 300 400 500 600 700 800

Electrolysis time (h)

Cell

volta

ge (m

V)


0.00

0.15

0.30

0.45

0.60

0.75

0.90

0 100 200 300 400 500 600 700 800


In-P

lane

vol

tage

(mV)

1000

1050

1100

1150

1200

1250

0 100 200 300 400 500 600 700 800


Cell

volta

ge (m

V)

850ºC, -0.25 A/cm2, 70% CO2 / 30% CO



850ºC, -0.25 A/cm2, 70% CO2 / 30% CO

-0.25

-0.20

-0.15

-0.10

-0.05

0.00

0.05

0.100 0.2 0.4 0.6 0.8 1

Z' (Ω ·cm2)

Z'' (Ω

·cm

2 )

12 Hz1.2 Hz

120 Hz1.2 kHz

1.2 kHz

0 h250 h500 h

020406080

100120140160180200

1 10 100 1000 10000 100000Frequence (Hz)

Δt ∂

Z'(f)

/ ∂l

n(f)

( Ω·c

m2 )

Timet = 500 h


Degradation: 175 mV


→(g) (ads)

Electrolysis:S S

850ºC, -0.25 A/cm2, 70% CO2 / 30% CO

-0.25

-0.20

-0.15

-0.10

-0.05

0.00

0.05

0.100 0.2 0.4 0.6 0.8 1

Z' (Ω ·cm2)

Z'' (Ω

·cm

2 )

12 Hz1.2 Hz

120 Hz1.2 kHz

1.2 kHz

0 h250 h500 h



→

→

(g) (ads)

2

(ads) 2 2 (g)

Electrolysis:S S

Introduction of H :S + H H S

850ºC, -0.25 A/cm2, 70% CO2 / 30% CO

-0.25

-0.20

-0.15

-0.10

-0.05

0.00

0.05

0.100 0.2 0.4 0.6 0.8 1

Z' (Ω ·cm2)

Z'' (Ω

·cm

2 )

12 Hz1.2 Hz

120 Hz1.2 kHz

1.2 kHz

0 h250 h500 h


875

900

925

950

975

1000

1025

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400Time (h)

Cell

volta

ge (m

V)

850ºC, -0.25 A/cm2, 45% CO2 / 45%H2 O / 10% H2

Electrolysis durability at low current density — Carbon dioxide + steam

875

900

925

950

975

1000

1025

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400Time (h)

Cell

volta

ge (m

V)

-0.2

0.0

0.2

0.4

0.6

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400

Time (h)

In-p

lane

vol

tage

(mV

)

850ºC, -0.25 A/cm2, 45% CO2 / 45%H2 O / 10% H2


850ºC, -0.25 A/cm2, 45% CO2 / 45%H2 O / 10% H2

-0.20

-0.15

-0.10

-0.05

0.00

0.050 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Z' (Ω ·cm2)

Z'' (Ω

·cm

2 )0 h200 h1340 h

12 Hz1.2 Hz

120 Hz1.2 kHz

1.2 kHz

0

20

40

60

80

100

120

140

1 10 100 1000 10000 100000Frequence (Hz)

Δt ∂

Z'(f)

/ ∂l

n(f)

( Ω·c

m2 )

Time

t = 200 h


Maximal degradation: 75 mV

(gas) (ads)

Electrolysis :Impurities Impurities →

850ºC, -0.25 A/cm2, 45% CO2 / 45%H2 O / 10% H2

-0.20

-0.15

-0.10

-0.05

0.00

0.050 0.1 0.2 0.3 0.4 0.5 0.6 0.7

Z' (Ω ·cm2)

Z'' (Ω

·cm

2 )0 h200 h1340 h

12 Hz1.2 Hz

120 Hz1.2 kHz

1.2 kHz


Electrolysis durability at high current density

Electrolysis durability at high current density — Steam or Carbon dioxide (Steam + Carbon dioxide)

1400

1500

1600

1700

1800

1900

2000

0 50 100 150 200 250 300 350 400 450


Cel

l vol

tage

(mV)

CO2 electrolysis

H2O electrolysis

850ºC, -1. 50 A/cm2, 50%H2 O / 50% H2

850ºC, -1. 50 A/cm2, 70%CO2 / 30% CO


1400

1500

1600

1700

1800

1900

2000

0 50 100 150 200 250 300 350 400 450


Cel

l vol

tage

(mV)

CO2 electrolysis

H2O electrolysis

850ºC, -1. 50 A/cm2, 50%H2 O / 50% H2

850ºC, -1. 50 A/cm2, 70%CO2 / 30% CO

-0.15

-0.10

-0.05

0.00

0.050 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5

Z' (Ω ·cm2)

Z'' (Ω

·cm

2 )

0 h200 h400 h

1400

1500

1600

1700

1800

1900

2000

0 50 100 150 200 250 300 350 400 450


Cel

l vol

tage

(mV)

CO2 electrolysis

H2O electrolysis

850ºC, -1. 50 A/cm2, 50%H2 O / 50% H2

850ºC, -1. 50 A/cm2, 70%CO2 / 30% CO


1400

1500

1600

1700

1800

1900

2000

0 50 100 150 200 250 300 350 400 450


Cel

l vol

tage

(mV)

CO2 electrolysis

H2O electrolysis

850ºC, -1.50 A/cm2, 50%H2 O / 50% H2

850ºC, -1.50 A/cm2, 70%CO2 / 30% CO


Summary

•Degradation at low current densities

No structural degradation

Degradation related to adsorption of impurities from the applied gasses (or in raw materials)

•Degradation at high current densities

Significant structural degradation

Related to the overpotential

solid oxide electrolysis cells: long-term...

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