IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010 1

Fuel Cell Research Activities at the University of Leoben

Focus: Solid Oxide Fuel Cells

Werner Sitte

Chair of Physical Chemistry, University of Leoben, Austria

IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010 2

Lifetime/degradationReduced degradation rate of thermally activated cell degradation mechanismsReduced corrosion rate of chromium-based alloys and steels for interconnectsMetal, metal-ceramic (compressible) seals and non crystallizing glassStability of contact coatingsLower sensitivity for combined thermal-redox cycles

CostsLifetimeCheap interconnect chromium alloys / steels and BOP materialsIndustrial, cost effective manufacturing processes

Fuel flexibility and high efficiencyH2 and reformatesInternal reforming of NG (simplest and most efficient system)

- Low catalytic activity for carbon deposition

State-of-the-art and motivation for research on IT-SOFCs

IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010 3

7 Universities

11 R&D organisations

3 Industrial companies, all SMEs

ECN NetherlandsHTceramix SwitzerlandCEA FranceEMPA SwitzerlandFZJ GermanyImperial College United Kingdom

Uni Karlsruhe GermanyUni St.Andrews United KingdomUni Oxford United KingdomUni Leoben AustriaCNRS Bordeaux FranceTOFC Denmark AECA (NTDA-SOFC) SpainNRC CanadaDICP ChinaIPMS UkraineSJTU ChinaBIC RussiaPMI BelarusVTT FinlandRisø - DTU Denmark

Project Consortium

Participation of University of Leoben in the Integrated Project SOFC600 (2006-2010)

SOFC600: Component and cell development

10-100 cm2 cellASR < 0.5 ohm.cm2

Degradation rate < 1 mohm.cm2/khr

LSC

LSCF

PSCF

LNF

LN

PN

LSC-GCO

Cr-resistance

Porosity

Nano-LSC

YDC

Barrier LayerGrain size

20GCO

NN

Screen printing

PVDPowder

Layer Thickness

Sintering

Reactivity

Lateral conductivity

Anode substrate

Wet deposition

Ni/YSZ

Microstructure

Particle size

Milling

Ni/ScZ

Ni/GCO

LST

Poreformer

SYT

Impedance

Robustness

Redox

Ni-salt

ImpregnationS-tolerance

Coking

Milling

S/C

PolarisationCeria

CatalystInternal reforming

Dilatometry

Expansion

MgO

Grain boundary Aging

Ionic radius

Dopant

Partial oxygen pressure

Ce-reduction

Grain size

10Sc1CeZr

Oxygen ionic conductivity

LiMOCVD

Thin film

8YSZStabilityKinetics

Yb-ZrHf-Zr

Y-Ce-Sc-ZrEB-PVD

Phase transition

J-V curve

Cell housing

Contacting

Current collector gridCell temperature

Area specific resistance

Cell area

Cell housing

Cell integrationGas flow

Sealing

Cell compositionCo-firing

Oxide anode

Reference cells

CO2

© Integrated Project SOFC600 (SES6-2006-020089), F. van Berkel

IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010 5

SOFC cell at 600oCArea Specific Resistance (ASR) below 0,5 Ω.cm2

Degradation rate below 0.05% / 1000 hours (1 mohm.cm2/khr)Robustness: 200 redox cycles, internal reforming capability, reduced coke formation activity

Aim for components:Anode (WP1.1) < 0.3 ohm.cm2

Cathode (WP1.2) < 0.15 ohm.cm2

Electrolyte (WP1.3) < 0.1 ohm.cm2

Cell (WP1.4) < 0.5 ohm.cm2

550 600 650 700 750 800

250

500

750

1000

1250

1500

1750

2000

2250

2500

status 2003/04 (CORE-SOFC)

projecttarget

AS

R /

mΩ

cm

2

Temperature / °C

tentative status 2005 (REALSOFC)

Overall Achievements Cell Development SOFC600

IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010 6

SOFC CathodesOxygen exchange properties

of BSCF, LSCF, NDNincluding

long time stability in real atmospheres

SOFC Electrolytes Sc-ZrO2

bulk and grain boundary conductivity = f(T, pO2)ageing studies

poröses NiO/YSZH2 e-

e-e-

H2O

dichtes YSZ

poröses dotiertes CeO2

poröses LSCF

e-e-

e-O2

O2-

Quelle: ECN Niederlande

University of Leoben: SOFC Activities

IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010 7

BSCF in different atmospheresCO2-free atmosphere: Reversible oxygen exchange of perovskite phase (ABO3-δ)

CO2-rich atmosphere: Onset of oxygen exchange shifted towards higher T

E. Bucher et al., in Proc. 8th Eur. SOFC Forum, 2008, p. A0603.

)pO,T(f]V[

Oe2V(g)O

2O

xOO22

1

=δ=

⇔′++••

••

SOFC cathodes: BSCF

IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010 8

Long term stability of the oxygen exchange kinetics of Nd2NiO4+δ(NDN) and La0.58Sr0.4Co0.2Fe0.8O3-δ (LSCF) in dry and wet atmospheres at 700°C

T=700°C

SOFC cathodes: LSCF vs. NDN

A. Egger et al., J. Electrochem. Soc., in press (2010)

IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010 9

0.0 0.5 1.0 1.5 2.0 2.50.0

0.5

1.0

1.5

2.0

2.5Rel

CPEgb

Rgb

CPEel CPEbulk

Rbulk Lss

p(O2) = 0.21 bar, T = 300°C 1%-H2/Ar , T = 300°C

-Z'' /

MΩ

cm

Z' / MΩ cm0.0 0.5 1.0 1.5 2.0 2.5

0.0

0.5

1.0

1.5

2.0

2.5Rel

CPEgb

Rgb

CPEel CPEbulk

Rbulk Lss

-Z'' /

MΩ

cm

Z' / MΩ cm

p(O2) = 0.21 bar, T = 300°C 1%-H2/Ar , T = 300°C

Ce0.12Y0.08Sc0.6Zr3.2O7.66Y0.2Sc0.6Zr3.2O7.60

Impedance spectra in oxidizing and reducing atmospheres (300 C)

Sc-doped zirconia electrolytes

[W. Preis, A. Egger, J. Waldhäusl, W. Sitte, E. de Carvalho, J.T.S. Irvine, SOFC XI, ECS Transactions 25 (2009) 1635-1642]

IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010 10

1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8-8

-6

-4

-2

0

2

4

EA = (1.05 ± 0.02) eV560 < T/°C < 700

EA = (1.27 ± 0.01) eV300 < T/°C < 560

EA = (0.92 ± 0.02) eV560 < T/°C < 700

EA = (1.24 ± 0.01) eV300 < T/°C < 560

heating in air (300 → 700°C) cooling in 1% - H2 / Ar (700 → 300°C)

ln(σ

T / S

cm

-1 K

)

103 (T / K)-11.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8

-8

-6

-4

-2

0

2

4

EA = (1.27 ± 0.01) eV300 < T/°C < 560

EA = (0.99 ± 0.03) eV560 < T/°C < 700

EA = (1.27 ± 0.01) eV300 < T/°C < 560

EA = (0.99 ± 0.03) eV560 < T/°C < 700

103 (T / K)-1

ln

( σT

/ S c

m-1 K

)

heating in air (300 → 700°C) cooling in 1% - H2 / Ar (700 → 300°C)

Ce0.12Y0.08Sc0.6Zr3.2O7.66Y0.2Sc0.6Zr3.2O7.60

Comparison between Y0.2Sc0.6Zr3.2O7.60 and Ce0.12Y0.08Sc0.6Zr3.2O7.66: heating in air (oxidizing conditions) and cooling in 1%-H2/Ar after reduction at 700°C for approx. 4 days

Bulk conductivity as a function of temperature in oxidizing and reducing atmospheres

Sc-doped zirconia electrolytes

IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010 11

Comparison between Y0.2Sc0.6Zr3.2O7.60 and Ce0.12Y0.08Sc0.6Zr3.2O7.66: heating in air (oxidizing conditions) and cooling in 1%-H2/Ar after reduction at 700°C for approx. 4 days

Ce0.12Y0.08Sc0.6Zr3.2O7.66Y0.2Sc0.6Zr3.2O7.60

1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8

-8

-6

-4

-2

0

2

4

6

EA = (1.28 ± 0.01) eV

EA = (1.28 ± 0.01) eV

heating in air (300 → 700°C) cooling in 1% - H2 / Ar (700 → 300°C)

ln(σ

T / S

cm

-1 K

)

103 (T / K)-11.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8

-8

-6

-4

-2

0

2

4

6

EA = (1.30 ± 0.01) eV

EA = (1.27 ± 0.01) eV

heating in air (300 → 700°C) cooling in 1% - H2 / Ar (700 → 300°C)

ln(σ

T / S

cm

-1 K

)

103 (T / K)-1

Grain boundary conductivity as a function of temperature in oxidizing and reducing atmospheres

Sc-doped zirconia electrolytes

IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010 12

-24 -20 -16 -12 -8 -4 0

0.01

0.1

T = 700°C

σ bul

k / S

cm

-1

log[p(O2) / bar]

Y0.20Sc0.6Zr3.2O7.60 Ce0.08Y0.12Sc0.6Zr3.2O7.64 Ce0.10Y0.10Sc0.6Zr3.2O7.65 Ce0.12Y0.08Sc0.6Zr3.2O7.66 Ce0.16Y0.042Sc0.6Zr3.2O7.68 Ce0.20Sc0.6Zr3.2O7.70

Bulk conductivity

-24 -20 -16 -12 -8 -4 0

0.01

0.1

σ tot

al /

S c

m-1

log [p(O2) / bar]

Y0.20Sc0.6Zr3.2O7.60 Ce0.08Y0.12Sc0.6Zr3.2O7.64 Ce0.10Y0.10Sc0.6Zr3.2O7.65 Ce0.12Y0.08Sc0.6Zr3.2O7.66 Ce0.16Y0.042Sc0.6Zr3.2O7.68 Ce0.20Sc0.6Zr3.2O7.70

Total (bulk + gb) conductivity

All samples containing ceria show a remarkable decrease of theionic conductivity at p (O2) < 10-15 bar

This effect is even more pronounced for grain boundaries

Electrical conductivity as a function of p(O2) at 700°C

Sc-doped zirconia electrolytes

IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010 13

0 1000 2000 3000 4000 5000 6000

0.02

0.04

0.06

0.081%-H2/Ar

bulk grain boundaries total (= bulk + gb)

σ / S

cm

-1

t / hours

air

Aging study of (CeO2)0.01(Sc2O3)0.10(ZrO2)0.89 at 700° under 1%-H2/Ar

Sc-doped zirconia electrolytes

[W. Preis, A. Egger, J. Waldhäusl, W. Sitte, E. de Carvalho, J.T.S. Irvine, SOFC XI, ECS Transactions 25 (2009) 1635-1642]

IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010 14

Outlook: Research on SOFC components for stationary and mobile applications

SOFC CathodesCathodes for solid oxide fuel cells with respect to long term stability under real operating conditions including failure analysis of degraded cathodes

- Partners: AVL List GmbH and FZ Jülich

Structure-property relations of thin film SOFC cathodes(oxygen exchange properties, defect chemistry)

- Partners: Joanneum Research Forschungsgesellschaft mbH, TU Wien

SOFC ElectrolytesDevelopment of co-doped Sc-zirconia electrolytes(bulk and grain boundary conductivity as function of temperature and oxygen partial pressure, defect chemistry, ageing studies)

- Partner: University of St. Andrews, UK

IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010 1515

Research Co-operations

Financial Support

...

...

Acknowledgment

http://www.steiermark.at/http://www.klimafonds.gv.at/home/aktuelles.htmlhttp://www.mcl.at/

IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010 16

Thank you for your attention!

Foliennummer 1Foliennummer 2Foliennummer 3SOFC600: Component and cell development �Foliennummer 5Foliennummer 6BSCF in different atmospheresFoliennummer 8Foliennummer 9Foliennummer 10Foliennummer 11Foliennummer 12Foliennummer 13Foliennummer 14Foliennummer 15Foliennummer 16