This document summarizes a presentation given by Gurpreet Kaur on the performance studies of copper-iron/ceria-yttria stabilized zirconia anode for solid oxide fuel cells. The objectives were to fabricate SOFCs in the lab using tape casting and to prepare Cu/CeO2-YSZ and Cu-Fe/CeO2-YSZ anodes for characterization and performance testing in hydrogen and methane fuels. Characterization showed that addition of iron to Cu-based anodes improved catalyst dispersion and electrical conduction. Performance testing found that power density increased from 190 to 330 mW/cm2 with increasing iron content in the Cu-Fe/CeO2-YSZ anode composition

1. Performance Studies of Copper-Iron/CeriaYttria Stabilized Zirconia Anode for Electrooxidation of Hydrogen and Methane Fuels in
Solid Oxide Fuel Cells
Presented by
Gurpreet Kaur
Department of Chemical Engineering
Indian Institute of Technology Delhi
International Conference on
December 10-11, 2013
Advances in Energy Research
Department of Chemical Engineering
Indian Institute of Technology-Delhi, New Delhi 110 016, India

2. Solid Oxide Fuel Cell
Solid oxide fuel cell is a device that converts gaseous fuels (hydrogen, natural gas)
via an electro-chemical process directly into electricity.
Principle of SOFC
Salient Features of SOFC
 SOFCs are over 60 % efficient
(conversion of fuel to electricity)
Operating Temperature:
700-1000 C
 Provides environment friendly power
generation
Conventional SOFC Components
Anode Side Reactions Cathode Side Reactions
2 H 2 2O 2
CH 4 4O
2
C4 H10 13O 2
2 H 2 O 4e
O2
4e
2O 2
CO2 2 H 2 O 8e
O2
8e
4O 2
O2
26e
4CO2 5H 2O 26e
13O 2
Electrolyte – 8 % Yttria Stabilized Zirconia (YSZ)
– a pure ionic conductor
Anode – Ni provides electronic conductivity and
enables electrochemical oxidation of fuel.
Cathode - La0.8Sr0.2MnO3 (LSM) provides
electronic conductivity and enables electrochemical
reduction of O2.
Applications
Stationary electrical power generation
Department of Chemical Engineering
Indian Institute of Technology-Delhi, New Delhi 110 016, India
1

3. Why Direct Hydrocarbons ?
Production of hydrogen by steam reforming reactions of natural gas and
higher hydrocarbons requires additional purification steps to satisfy fuel
cell demands
Direct hydrocarbon solid oxide fuel cell can operate in hydrocarbon fuels without the need
for pre-reforming.
Anode requirements for oxidation of hydrocarbons




High electro catalytic activity for oxidation of fuel
Good electronic conductivity for transport of electrons from the TPB
Good ionic conductivity for transport of oxide ions to the TPB
Sufficient porosity for diffusion of fuel gases and exhaust gases to and from the
TPB
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4. Literature Review
nodes for Direct Hydrocarbon Solid Oxide Fuel C
Nickel/Yttria-stabilized Zirconia based Anodes1
High catalytic activity for fuel oxidation and for steam reforming of methane
Relatively inexpensive; chemically and physically compatible with YSZ electrolyte
Problems in use with dry hydrocarbons; Tends to promote carbon deposition1
Copper/Ceria/Yttria Stabilized Zirconia2Alternative anode material for direct
hydrocarbons
CeO2 : Mixed ionic and electronic conductor in reducing medium.
Good oxidation catalyst for hydrocarbons
Poorer electronic conductor
Cu: To increase the electronic conductivity, addition of Cu is necessary
Cu/CeO2-YSZ anodes are stable in variety of hydrocarbons
Limited by lower Van Dillen and (~ 100 mW/cm Today 2000; 76,
1. M .L.Toebes, J.H. Bitter, A.J.performanceK.P.de Jong, Catal. 2 at 800 C). 33 – 42 .
2. R. J. Gorte, S. Park, J. M. Vohs, C. Wang, Adv Mater. 2000; 12: 1465 -69
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5. Objective of Research Work
 Fabrication of complete solid oxide fuel cell in laboratory scale using tape casting technique of thickness of
< 600 µm and anode porosity of 70 %. Additives composition is optimized to get defect free SOFC
 Preparation of Cu/CeO2-YSZ and Cu-Fe/CeO2-YSZ anodes using wet impregnation method.
 Characterization of prepared anodes using thermal gravimetric analysis (TGA), X-ray diffraction (XRD),
scanning electron microscopy (SEM), elemental dispersive X-ray (EDX) to investigate the thermal, structural,
morphological properties and elemental analysis
 Current-Voltage characterization of prepared anodes with YSZ electrolyte and LSM-YSZ cathodes in H2 and
methane fuels.
 Frequency response analysis of SOFC with prepared anodes to study various resistances e.g. ohmic
resistance, polarization resistance.
 Study the effect of temperature, bimetallic molar ratio and addition of precious metals on the performance
of SOFC in H2 and methane fuels.
 Investigation of carbon deposition using optical microscopy and thermal gravimetric analysis.
 Longevity testing in methane fuel.
Gurpreet Kaur and Suddhasatwa Basu, Journal of Power Sources, 241, 783-790, 2013
Department of Chemical Engineering
Indian Institute of Technology-Delhi, New Delhi 110 016, India
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6. Preparation Procedure for Anode and Electrolyte Slurry for Tape Casting
Solvent (Ethanol and MEK)
+
Dispersant (oleic acid)
Stirring
Magnetic
Stirring, 24 h
Yttria-Stabilized Zirconia
Pore-formers i.e. Graphite
and
Polystyrene)
for anode only
SOFC Fabrication
Binder (Polyethylene Glycol
and Polyvinyl butryl)
Stirring
Homogeneous Slurry
Magnetic
Stirring, 24 h
Composition of anode and
electrolyte for tape casting
slurry
Homogeneous Slurry
Component
Electrolyte Tape Casting and
Drying for 24 h
Porous YSZ Anode Tape
Casting and Drying for 24 h
Co-sintering, 1450 C
YSZ
Graphite
Polystyrene
Ethanol (EtOH)
Methylethyl
ketone (MEK)
Oleic acid
Polyvinyl
butyral (PVB)
Polyethylene
glycol (PEG)
Quantity
24 gm
5 gm
3.8 gm
Tape casted electrolyte
layer
Porous YSZ layer on
dense YSZ electrolyte
16 ml
9 ml
1.0 ml
3.8 gm
3 ml
No poreformers (graphite and polystrene)
SEM of porous and dense
added in electrolyte slurry
Fabrication issues
YSZ sintered at 1450 ºC
Green tape – Pin holes
Department of Chemical Engineering
Sintered layers – cracking, delamination etc
Indian Institute of Technology-Delhi, New Delhi 110 016, India
SEM of porous YSZ
Porosity 70 vol %
5

7. Preparation Procedure of Anode for SOFC
(Wet Impregnation Method)
Porous YSZ
Impregnation of 1M
Ce(NO3)3, 6H2O
Calcinations at 400 ºC for 2 h
TGA of impregnated nitrate solution in porous YSZ
Repeated impregnation
to get desired loading
Impregnation of 1M Cu(NO3), 3H2O
and Fe(NO3)3, 9H2O solution
Cu-Fe [1:1]
Calcinations at 400 ºC for 2 h
Anode Cu/CeO2-YSZ and CuFe/CeO2-YSZ
 Data was collected from room temperature to 1000 ̊C at a rate of
10 ̊C/min. Zero air flow rate: 50 ml/min
 Calcination temperature of 400 ºC is selected to get metal oxides
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8. Synthesis Procedure of Cathode (La0.8Sr0.2MnO3)
La0.8Sr0.2MnO3 showed good chemical and thermal compatibility with YSZ electrolyte material
2500
2000
XRD spectra of
La0.8Sr0.2MnO3
Calcination
1100 oC for 2 h
Intensity (cps)
Dissolve La(NO3)3, Sr(NO3)2,
Mn(NO3)2 in stoichiometric ratio
1000
500
 All peaks corresponds to perovskite phase
 Particles size of LSM ~0.3 µm
Mixing (Agate mortar)
La0.8Sr0.2MnO3– 0.45 g
YSZ – 0.45 g
Graphite– 0.1 g
1500
0
20
30
40
50
60
70
80
2θ( )
SEM of
La0.8Sr0.2MnO3
Slurry preparation
Mixed powders with
glycerol
* R.J. Bell, G.J. Millar, J. Drennan, Solid State Ionics 2000; 131: 211–220.
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Indian Institute of Technology-Delhi, New Delhi 110 016, India
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9. Experimental set up and Procedure
High Temperature SOFC Furnace
Electrolyte
YSZ
Cathode
LSM:YSZ
PGSTAT 30, Autolab (i-V and impedance
measurements)
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Indian Institute of Technology-Delhi, New Delhi 110 016, India
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10. X-ray Diffraction of Cu-Fe/CeO2-YSZ Anodes
¤
•
*,o
•
ɵ
(c)
¤ɵ
+
(•) YSZ
(*) Fe2O3
(o) CuFe2O4
(+) CuO
(¤) Cu
(ɵ) Fe
+
(b)
8000
•
6000
•
*
Intensity (a.u)
•
( ) YSZ ( ) Cu ( ) Fe (*) CeO2 (ο) Fe3O4 (¤) Fe2O3
*
(d)
*
*
4000
(c)
ο
2000
¤
¤ ο
¤
¤
(b)
(a)
(a)
0
25
35
45
55
65
75
2 Theta (Degree)
XRD patterns of (a) YSZ, (b) Cu-Fe/YSZ calcined at
300 C (c) Cu-Fe/YSZ reduced at 800 C
XRD patterns of (a) YSZ, (b) Fe/CeO2-YSZ, (c) Cu/CeO2YSZ and (d) Cu-Fe/CeO2-YSZ after reduction in H2 at
800 C
 Cu-Fe/CeO2-YSZ anodes were prepared for three molar ratios of Cu-Fe [1:0, 3:1 and 1:1].
 Peaks at 43.3º and 44.2 corresponds to Cu and Fe and in metals are present cubic structure.
 Small shift in the peaks for Cu and Fe was observed in the spectra, according to phase diagram1,
some Fe can be incorporated in Cu phase at 800 C.
1. Turchanin MA, Agraval PG, Nikolaenko IV, J Phase Equilibria 2003;24:307-19.
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Indian Institute of Technology-Delhi, New Delhi 110 016, India
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11. Scanning electron microscopy of Cu-Fe/CeO2-YSZ anodes after
reduction in H2 at 800ºC
20 wt% Cu-Fe [3:1]
20 wt% Cu-Fe [3:1]
10 wt% CeO2, 20 wt% Cu-Fe [1:0, 3:1 and 1:1]
 Addition of Fe in Cu based anodes improves the
catalyst dispersion
 Better interconnection between particles helps to
improve the electrical conduction and provides
more surface area for fuel oxidation reaction
 Particle size was observed to be 1 µm
20 wt% Cu-Fe [1:1]
Department of Chemical Engineering
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12. Elemental dispersive analysis of Cu/CeO2-YSZ and Cu-Fe/CeO2YSZ anodes
Presence of metals inside the pores with no significant impurity observed.
Results indicate the success of fabrication of anodes by wet impregnation method.
Department of Chemical Engineering
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13. Performance of SOFC in H2 at 800°C (Cu-Fe/CeO2/YSZ anodes for Cu-Fe
molar ratio of 1:0, 3:1 and 1:1, YSZ as electrolyte, LSM/YSZ as cathode
i-V (filled symbols) and power curves (open symbols) for different molar ratio of Cu-Fe
SEM of SOFC
Performance Curves
400
350
1
Voltage (V)
300
~90 µm
80 µm
0.8
250
0.6
200
150
0.4
100
0.2
40 µm
50
0
Power Density (mW/cm2)
1.2
0
0
200
400
Current Density
600
800
(mA/cm2)
 SEM of SOFC shows anode, electrolyte and cathode thickness of 90, 80 and 40 µm.
 Power density of ~ 190, 260 and 330 mW/cm-2 was observed for Cu-Fe/CeO2-YSZ anodes for Cu-Fe
molar ratio of 1:0, 3:1 and 1:1.
 Performance increased with increase in Fe loading in Cu/CeO2-YSZ anodes
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14. XRD of Cu-Fe/CeO2-YSZ anode after reduction in H2
EIS of SOFC for different molar ratio of
Cu-Fe of 1:0(∆), 3:1 (◊) and 1:1 (□)
0.3
-Zim (ohm cm2 )
-Zim (ohm cm2)
0.3
0.2
0.2
0.1
0
7
7.5
8
8.5
9
9.5
10
Zre (ohm cm2 )
0.1
RΩ
0
0
0.3
0.6
Rp
Zre
0.9
1.2
(ohm cm2)
1.5
1.8
Lattice parameter CeO2 calculated from XRD: 5.36Å
Pure CeO2 lattice parameter- 5.41 Å
 Calculated electrolyte resistance for 80 µm thick electrolyte is ~0.38 Ω. cm2.
 Less additional ohmic resistance was observed for Cu-Fe [1:1] due to better dispersion between catalyst particles
resulting better electronic conduction.
 Total polarization resistance decreases with increase in Fe molar ratio suggest that prepared anodes have better
electro-catalytic activity towards oxidation of H2.
 Improvement in the performance of cell might also be due to incorporation of Cu and Fe ions in CeO 2 lattice
Department of Chemical Engineering
Indian Institute of Technology-Delhi, New Delhi 110 016, India
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15. Characterization of Cu-Fe/CeO2-YSZ anodes after exposure to CH4 at 800 C
Optical microscopy images of Cu-Fe/CeO2-YSZ anodes for Cu-Fe molar ratio of (a) 1:0, (b) 3:1 (c) 1:1 after exposure
to CH4 for 1h
(a)
Table - Weight changes after CH4
flow
Metal wt% in
Weight
porous CeO2/YSZ
change
(%)
Cu: Fe [1:0]- (20wt%)
TGA of Cu-Fe/CeO2-YSZ anode after reduction in (a) H2 and (b) H2 followed
by exposure of CH4 for 1 h
-0.027
Cu: Fe [1:1]- (20wt%)
(c)
-0.030
Cu: Fe [3:1]- (20wt%)
(b)
-0.021
 No significant weight gain was observed due to carbon deposition after CH4 flow
Department of Chemical Engineering
Indian Institute of Technology-Delhi, New Delhi 110 016, India
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16. Performance of Cu-Fe/CeO2-YSZ anodes in CH4 at 800 ºC
150
Cu-Fe [1:1]
Voltage (V)
1
Cu-Fe [3:1]
Cu-Fe [1:0]
0.8
100
0.6
0.4
50
0.2
0
Power Density (mW/cm2)
1.2
0
0
50
100
150
200
250
300
350
Current Density (mA/cm2)
 Cu-Fe/CeO2/YSZ anodes for Cu-Fe molar ratio of 1:1 showed higher performance than 1:0 and 3:1.
 Performance of all the anodes are lower in CH4 than H2 might be due to less reactive nature of CH4
in comparison to H2.
 OCV was observed to be less than Nernst potential (> 1.05 V ) suggesting that complete oxidation of
CH4 is not taking place.
 Oxidation of hydrocarbon on surface may occur in multiple steps and equilibrium has been established
between hydrocarbons and partial oxidation products.
Department of Chemical Engineering
Indian Institute of Technology-Delhi, New Delhi 110 016, India
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17. Effect of addition of 1 wt% Pd on the performance of Cu-Fe/CeO2-YSZ
anodes in H2 and CH4
Performance curves of Cu-Fe/CeO2-YSZ anodes with (□) and without (○) 1 wt% Pd
200
0.8
150
H2
0.6
100
0.4
50
0.2
Cu-Fe [1:1]
0
100
200
300
400
500
120
100
0.8
80
CH4
0.6
60
0.4
40
0.2
20
Cu-Fe [1:1]
0
0
140
1
Voltage (V)
Voltage (V)
1
1.2
600
0
Power Density (mW/cm2)
250
Power Density (mW/cm2)
1.2
0
0
Current Density (mA/cm2)
100
200
300
400
Current Density (mA/cm2)
 Significant improvement in the cell
performance in CH4 was observed with
addition of 1 wt% of Pd
 Results suggest that resistance associated
with surface reactions decreases with
addition of 1 wt% Pd.
Anode 160 µm, Electrolyte 100 µm
Department of Chemical Engineering
Indian Institute of Technology-Delhi, New Delhi 110 016, India
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18. Long term performance of Cu-Fe/CeO2/YSZ anodes in CH4
0.4
Cu-Fe
[1:1]
150
100
0.5V
50
-Zim (ohm cm2)
0.2
-Zim (ohm cm2)
Power Density (mW/cm2)
200
0.3
0.2
0.15
22 h
1h
0.1
30 h
0.05
46 h
0
0.3
0.4
0.5
0.6
Zre (ohm cm2)
0.1
CH4, 800 C
0
0
10
20
30
Time (h)
40
50
0
0
0.5
1
1.5
2
Zre (ohm cm2)
 Power density decreased from 125 mW/cm2 to 100 mW/cm2 during 46 h testing
 Increase in ohmic resistance may be due to increase in particle size of catalyst particles at
800 C during stability test. (repeated thrice).
 Increase in ohmic resistance and polarization resistance might be responsible for this loss.
 Cu-Fe/CeO2/YSZ anode showed much better stability than Ni/YSZ anodes in which
complete performance degradation takes place within 5 h.
Department of Chemical Engineering
Indian Institute of Technology-Delhi, New Delhi 110 016, India
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19. SEM and TGA of Cu-Fe/CeO2-YSZ anodes after cell testing in
CH4 for 46 h
 SEM shows catalyst particle size
increased from 1.0 to 1.5 µm after cell
operation at 800 °C for 46 h
TGA shows no significant weight loss
suggesting that carbon ,if present, is not in
significant quantity.
Department of Chemical Engineering
Indian Institute of Technology-Delhi, New Delhi 110 016, India
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20. Summary
SOFC Fabrication and Electrochemical Characterization
 Solid oxide fuel cells was fabricated by tape casting and wet impregnation method.
 Additives (pore-formers, binder and solvent) composition was optimized to get defect free button
cells.
SOFC testing (i-V and EIS) was carried out for Cu/CeO2-YSZ and Cu-Fe/CeO2-YSZ anodes with
YSZ as electrolyte and LSM/YSZ as cathode.
Performance of Cu-Fe/CeO2-YSZ Anodes in H2 and Methane
 XRD shows the formation of Cu and Fe phase. Addition of Cu to Fe enhances the reduction of Fe.
 SEM shows that better dispersion between catalyst particles achieved with addition of Fe in
Cu/CeO2-YSZ anodes
 Addition of Fe in Cu/CeO2-YSZ anodes showed improved performance in H2 and CH4 fuels.
 Electrochemical impedance spectra showed less ohmic as well as charge transfer resistance for CuFe/CeO2-YSZ anodes in comparison to Cu/CeO2-YSZ anodes.
 SOFC performance increased with addition of 1 wt % Pd in Cu-Fe/CeO2-YSZ anodes.
 No significant degradation in the performance observed during cell operation in CH4 suggesting that
anodes are stable in comparison to conventional Ni/YSZ anodes.
Department of Chemical Engineering
Indian Institute of Technology-Delhi, New Delhi 110 016, India
19

21. References
[1] Lashtabeg, A. and Skinner, S. J. (2006) Solid oxide fuel cells-a challenge for materials chemists, Journal of materials chemistry,
16, pp. 3161-70.
[2] Baker, R. T. K. (1989) Catalytic growth of carbon filaments, Carbon, 27, pp.1315-23.
[3] Gorte, R. J., Vohs, J. M. (2003) Novel SOFC anodes for direct electrochemical oxidation of hydrocarbons, Journal of
catalysis, 216, pp. 477-86.
[4] Gorte, R. J., Park, S., Vohs, J. M. and Wang, C. (2000) Anodes for direct oxidation of dry hydrocarbons in solid oxide fuel
cells, Advanced Material, 12, pp.1465-69.
[5] Zhu, H., Wang, W., Ran, R., Su, C., Shi, H. and Shao, Z. (2012) Iron incorporated Ni-ZrO2 catalysts for electric
power generation from methane, International Journal of Hydrogen Energy, 37, pp. 9801-9808.
[6] Gordes, P., Christiansen, N., Jensen, E. J. and Villadsen, J. (1995) Synthesis of perovskite-type compounds by drip
Pyrolysis, Journal of Material Science, 30, pp.1053-58.
[7] Mitterdorfer, A. and Gauckler, L.G. (1998) La2Zr2O7 formation and oxygen reduction kinetics
of La0.85Sr0.15MnYO3,O2(g) YSZ system, Solid State Ionics, 111, pp. 185-218.
[8] Turchanin, M. A., Agraval, P. G. and Nikolaenko I. V. (2003) Thermodynamics of alloys and phase equilibria in the
copper iron system, Journal of Phase Equilibria, 24, pp. 307-309.
[9] Kameoka, S., Tanabe, T. and Tsai, A. P. (2005) Spinel CuFe2O4: a precursor for copper catalyst with high thermal
stability and activity, Catalysis Letters, 100, pp. 89-93.
[10] Lv, H., Tu, H., Zhao, B., Wu, Y. and Hu, K. (2007) Synthesis and electrochemical behavior of Ce1-xFex02-δ as a
possible SOFC anode materials, Solid State Ionics, 177, pp. 3467-3472.
[11] Xing, Z., Hua, W., Honggang, W., Kongzhai, L. and Xianming C. (2010) Hydrogen and syngas production from
two-step steam reforming of methane over CeO2-Fe2O3 oxygen carrier, Journal of Rare Earth, 28, pp. 907-913.
[12] Buccheri, M. A., Singh, A. and Hill, J. M. (2011) Anode- versus electrolyte-supported Ni-YSZ/YSZ/Pt SOFCs:
Effect of cell design on OCV, performance and carbon formation for the direct utilization of dry methane, Journal
of Power Sources, 196, pp. 968-976
Department of Chemical Engineering
Indian Institute of Technology-Delhi, New Delhi 110 016, India
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22. Thank You
Department of Chemical Engineering
Indian Institute of Technology-Delhi, New Delhi 110 016, India

23. Department of Chemical Engineering
Indian Institute of Technology-Delhi, New Delhi 110 016, India

24. Nernst Potential calculation for multiple reactions
E
1.15
G / nF
1.1
CH 4
OCV (V)
1.05
2O2
CO2
 CH 4 3 / 2O2
1
C O2
CO 1/ 2O2
0.9
CO 2 H 2 O
CO2
C 1/ 2O2
0.95
2 H 2O
 CH 4 O2
CO
CO2
C 2 H 2O
Experimental
0.85
850
900
950
1000
1050
1100
Temperature ( K)
An observed OCV is less than Nernst potential suggesting that complete oxidation
of methane is not taking place.
Multiple anode reactions may occur simultaneously with dominating contribution
from one reaction.
Department of Chemical Engineering
Indian Institute of Technology-Delhi, New Delhi 110 016, India