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
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State-of-the-art and motivation for research on IT-SOFCs
h Lifetime/degradation
ƒ Reduced degradation rate of thermally activated cell degradation
mechanisms
ƒ Reduced corrosion rate of chromium-based alloys and steels for
interconnects
ƒ Metal, metal-ceramic (compressible) seals and non crystallizing glass
ƒ Stability of contact coatings
ƒ Lower sensitivity for combined thermal-redox cycles
h
Costs
ƒ Lifetime
ƒ Cheap interconnect chromium alloys / steels and BOP materials
ƒ Industrial, cost effective manufacturing processes
h Fuel flexibility and high efficiency
ƒ H2 and reformates
ƒ Internal reforming of NG (simplest and most efficient system)
- Low catalytic activity for carbon deposition
IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010
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Participation of University of Leoben in the
Integrated Project SOFC600 (2006-2010)
Project Consortium
7 Universities
11 R&D organisations
3 Industrial companies, all SMEs
ECN
HTceramix
CEA
EMPA
FZJ
Imperial College
Netherlands
Switzerland
France
Switzerland
Germany
United Kingdom
Uni Karlsruhe
Uni St.Andrews
Uni Oxford
Uni Leoben
CNRS Bordeaux
TOFC
AECA (NTDA-SOFC)
NRC
DICP
IPMS
SJTU
BIC
PMI
VTT
Risø - DTU
IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010
Germany
United Kingdom
United Kingdom
Austria
France
Denmark
Spain
Canada
China
Ukraine
China
Russia
Belarus
Finland
Denmark
3
SOFC600: Component and cell development
J-V curve
Cell housing
Porosity
PSCF
LN
Phase transition
Wet deposition
Catalyst
Ceria
PN
LNF
PVD
Grain size
LSC-GCO
LSCF
Powder
20GCO
Impedance
Sintering
Barrier Layer
Ni-salt
Lateral conductivity
Reactivity
Cr-resistance
Coking
Ni/YSZ
Anode substrate
MgO
S-tolerance
Thin film
Internal reforming
Polarisation
Milling
Redox
Ni/ScZ
Microstructure
Impregnation
8YSZ
LiMOCVD
Ni/GCO
Expansion
Oxide anode
Ce-reduction
Grain size
YDC
Layer Thickness
Aging
Partial oxygen pressure
10-100 cm2 cell
ASR < 0.5 ohm.cm2
Degradation rate < 1 mohm.cm2/khr
Nano-LSC
LSC
Hf-Zr
Cell composition
Sealing
Screen printing
CO2
Yb-Zr
10Sc1CeZr
Grain boundary
Cell integration
Co-firing
Stability
Y-Ce-Sc-Zr
Dopant
Gas flow
Kinetics
Oxygen ionic conductivity
Ionic radius
EB-PVD
Area specific resistance
Contacting
NN
Cell area
Current collector grid
Cell temperature
Reference cells
Cell housing
LST
© Integrated Project SOFC600 (SES6-2006-020089), F. van Berkel
Robustness
Particle size
Poreformer
Milling
S/C
SYT
Dilatometry
Overall Achievements Cell Development SOFC600
h SOFC cell at 600oC
ƒ Area Specific Resistance (ASR) below 0,5 Ω.cm2
ƒ Degradation rate below 0.05% /
1000 hours (1 mohm.cm2/khr)
ƒ Robustness: 200 redox cycles,
internal reforming capability,
reduced coke formation activity
2500
2250
Aim for components:
Anode (WP1.1)
<
Cathode (WP1.2) <
Electrolyte (WP1.3) <
Cell (WP1.4)
<
status 2003/04 (CORE-SOFC)
ASR / mΩ cm
2
2000
1750
1500
1250
tentative status 2005 (REALSOFC)
1000
750
500
0.3 ohm.cm2
0.15 ohm.cm2
0.1 ohm.cm2
0.5 ohm.cm2
project
target
250
550
600
650
700
750
800
Temperature / °C
IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010
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University of Leoben: SOFC Activities
e-
e-
poröses NiO/YSZ
H2
e-
H 2O
SOFC Cathodes
Oxygen exchange properties
of BSCF, LSCF, NDN
including
ƒ long time stability in
real atmospheres
O2-
dichtes YSZ
poröses dotiertes CeO2
SOFC Electrolytes
Sc-ZrO2
ƒ bulk and grain boundary
conductivity = f(T, pO2)
ƒ ageing studies
O2
e-
poröses LSCF
IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010
e-
eQuelle: ECN Niederlande
6
SOFC cathodes: BSCF
BSCF in different atmospheres
h CO2-free atmosphere: Reversible oxygen exchange
of perovskite phase (ABO3-δ)
1
2
O 2 (g) + VO•• + 2e′ ⇔ OOx
[ VO•• ] = δ = f (T, pO 2 )
h CO2-rich atmosphere:
ƒ Onset of oxygen
exchange shifted
towards higher T
E. Bucher et al., in Proc. 8th Eur. SOFC Forum, 2008, p. A0603.
IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010
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SOFC cathodes: LSCF vs. NDN
h 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
A. Egger et al., J. Electrochem. Soc., in press (2010)
IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010
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Sc-doped zirconia electrolytes
Impedance spectra in oxidizing and reducing atmospheres (300 C)
Y0.2Sc0.6Zr3.2O7.60
Ce0.12Y0.08Sc0.6Zr3.2O7.66
2.5
2.5
Rbulk
Lss
Rgb
Rel
CPEgb
CPEel
-Z'' / MΩ cm
-Z'' / MΩ cm
CPEbulk
p(O2) = 0.21 bar, T = 300°C
1%-H2/Ar , T = 300°C
1.0
Rel
CPEbulk
CPEgb
CPEel
1.5
p(O2) = 0.21 bar, T = 300°C
1%-H2/Ar , T = 300°C
1.0
0.5
0.5
0.0
0.0
Rgb
2.0
2.0
1.5
Rbulk
Lss
0.5
1.0
1.5
Z' / MΩ cm
2.0
2.5
0.0
0.0
0.5
1.0
1.5
2.0
2.5
Z' / MΩ cm
[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
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Sc-doped zirconia electrolytes
Bulk conductivity as a function of temperature
in oxidizing and reducing atmospheres
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
Y0.2Sc0.6Zr3.2O7.60
Ce0.12Y0.08Sc0.6Zr3.2O7.66
heating in air (300 → 700°C)
cooling in 1% - H2 / Ar (700 → 300°C)
4
heating in air (300 → 700°C)
cooling in 1% - H2 / Ar (700 → 300°C)
EA = (0.92 ± 0.02) eV
4
EA = (0.99 ± 0.03) eV
560 < T/°C < 700
560 < T/°C < 700
-2
EA = (1.27 ± 0.01) eV
560 < T/°C < 700
300 < T/°C < 560
-4
0
EA = (1.24 ± 0.01) eV
-1
EA = (0.99 ± 0.03) eV
ln(σT / S cm K)
2
0
-1
ln(σT / S cm K)
2
-2
560 < T/°C < 700
-4
EA = (1.27 ± 0.01) eV
-6
EA = (1.27 ± 0.01) eV
-6
300 < T/°C < 560
-8
300 < T/°C < 560
EA = (1.05 ± 0.02) eV
300 < T/°C < 560
-8
1.0
1.1
1.2
1.3
1.4
3
1.5
10 (T / K)
-1
1.6
1.7
1.8
1.0
1.1
1.2
1.3
1.4
3
10 (T / K)
IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010
1.5
1.6
1.7
1.8
-1
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Sc-doped zirconia electrolytes
Grain boundary conductivity as a function of temperature
in oxidizing and reducing atmospheres
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
Y0.2Sc0.6Zr3.2O7.60
heating in air (300 → 700°C)
cooling in 1% - H2 / Ar (700 → 300°C)
6
4
4
2
2
-1
EA = (1.27 ± 0.01) eV
0
-2
EA = (1.30 ± 0.01) eV
-4
-2
-8
-8
1.2
1.3
1.4
3
1.5
10 (T / K)
1.6
1.7
1.8
EA = (1.28 ± 0.01) eV
-4
-6
1.1
EA = (1.28 ± 0.01) eV
0
-6
1.0
heating in air (300 → 700°C)
cooling in 1% - H2 / Ar (700 → 300°C)
6
ln(σT / S cm K)
-1
ln(σT / S cm K)
Ce0.12Y0.08Sc0.6Zr3.2O7.66
1.0
1.1
1.2
1.3
-1
IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010
1.4
3
1.5
10 (T / K)
1.6
1.7
1.8
-1
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Sc-doped zirconia electrolytes
Electrical conductivity as a function of p(O2) at 700°C
Bulk conductivity
Total (bulk + gb) conductivity
0.1
0.1
-1
σtotal / S cm
σbulk / S cm
-1
T = 700°C
Y0.20Sc0.6Zr3.2O7.60
Ce0.08Y0.12Sc0.6Zr3.2O7.64
0.01
Ce0.10Y0.10Sc0.6Zr3.2O7.65
Y0.20Sc0.6Zr3.2O7.60
Ce0.08Y0.12Sc0.6Zr3.2O7.64
0.01
Ce0.10Y0.10Sc0.6Zr3.2O7.65
Ce0.12Y0.08Sc0.6Zr3.2O7.66
Ce0.12Y0.08Sc0.6Zr3.2O7.66
Ce0.16Y0.042Sc0.6Zr3.2O7.68
Ce0.16Y0.042Sc0.6Zr3.2O7.68
Ce0.20Sc0.6Zr3.2O7.70
-24
-20
-16
-12
-8
log[p(O2) / bar]
-4
Ce0.20Sc0.6Zr3.2O7.70
0
-24
-20
-16
-12
-8
-4
0
log [p(O2) / bar]
ƒ All samples containing ceria show a remarkable decrease of the
ionic conductivity at p (O2) < 10-15 bar
ƒ This effect is even more pronounced for grain boundaries
IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010
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Sc-doped zirconia electrolytes
Aging study of (CeO2)0.01(Sc2O3)0.10(ZrO2)0.89 at 700° under 1%-H2/Ar
0.08
air
1%-H2/Ar
0.06
σ / S cm
-1
0.04
0.02
bulk
grain boundaries
total (= bulk + gb)
0
1000
2000
3000
4000
5000
6000
t / hours
[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
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Outlook: Research on SOFC components
for stationary and mobile applications
SOFC Cathodes
ƒ Cathodes 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
ƒ Structure-property relations of thin film SOFC cathodes
(oxygen exchange properties, defect chemistry)
- Partners: Joanneum Research Forschungsgesellschaft mbH,
TU Wien
SOFC Electrolytes
ƒ Development 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
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Acknowledgment
Research Co-operations
...
Financial Support
...
IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010
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Thank you for your attention!
IEA Workshop Advanced Fuel Cells, TU Graz, 01.09.2010
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