La 0.8 Sr 0.2 CoO 3 Coated Nickel Cathodes for Molten Carbonate Fuel Cells
22
Prabhu Ganesan, Hector Colon, Bala Haran, R. E. White and Branko Popov Department of Chemical Engineering University of South Carolina, Columbia, SC 29208. La 0.8 Sr 0.2 CoO 3 Coated Nickel Cathodes for Molten Carbonate Fuel Cells
description
La 0.8 Sr 0.2 CoO 3 Coated Nickel Cathodes for Molten Carbonate Fuel Cells. Prabhu Ganesan, Hector Colon, Bala Haran, R. E. White and Branko Popov Department of Chemical Engineering University of South Carolina, Columbia, SC 29208. Presentation Outline. Objectives - PowerPoint PPT Presentation
Transcript of La 0.8 Sr 0.2 CoO 3 Coated Nickel Cathodes for Molten Carbonate Fuel Cells
Prabhu Ganesan, Hector Colon, Bala Haran, R. E. White and Branko Popov Department of Chemical Engineering
University of South Carolina, Columbia, SC 29208.
La0.8Sr0.2CoO3 Coated Nickel Cathodes for Molten Carbonate
Fuel Cells
Presentation Outline
Objectives Prepare a stable cathode material with lower
solubility and comparable performance as NiO
Coating of La0.8Sr0.2CoO3 using sol-gel process
Characterization Studies Polarization performance AAS – Solubility measurements SEM – Microstructure analysis EIS Full cell studies
State-of-the Art Molten Carbonate Fuel Cells
Component Material / Properties Problem/Solution
Anode Material Ni+10wt% CrPore size 3 ~ 6 mPorosity 50~70%Thickness 0.5~1.5 mmSp. Area 0.1~1 m2/g
• Creep/Sintering - Ni-Al Alloy• Electrolyte retaining - Coating of Oxides
Cathode Material Lithiated NiOPore size 6 ~ 9 mPorosity 80~85% as NiThickness 0.5~0.8 mmSp. Area 0.5 m2/g
• NiO dissolution - Stabilized NiO - LiCoO2 cathode - Modified electrolyte
Matrix Material -LiAlO2
Pore size 0.2 ~ 0.5 mPorosity 50~60%Thickness 0.5 mmSp. Area 0.1~10 m2/g
• Sintering/Thermal Stability - Fiber or large particles• Phase stability - -LiAlO2
CurrentCollector
Material SS316 •Chromium Dissolution - Nickel Cladding (Anode) - Fe-Al alloys
Cathode Materials for Molten Carbonate Fuel Cells
• State-of-the-art NiO(Li)
Alternate Cathodes
• LiCoO2, LiNiO2
• LiCoO2 Coated Nickel Oxide
• Ni-Ce and Ni – La2O3
• Ni-Nb Surface Alloy
• Perovskites such as La0.8Sr0.2CoO3
• Cobalt Encapsulated Nickel
• Mixed Lithium Nickel Cobalt Oxides
USC Molten Carbonate Fuel Cell(Half Cell)
Porous Ni Cathode
Perforated SUS 304 Current Collector
USC Molten Carbonate Fuel Cell(Full Cell)
Flow chart for Ni electrode preparation
Ni Powder Dispersant + Water
Milling 24 h
Binder Milling 12 h
Plasticizer Milling 12 h
Filtering
Casting
De-airing
Drying Sintering
80
84
88
92
96
100
104
0 200 400 600 800
Temperature (oC)
wt
rem
ain
ing
(%
)
-70
-60
-50
-40
-30
-20
-10
0
10
dw
/dT
*10
00
(m
g/o
C)Nickel
r = 10 oC/min
TGA Behavior of Ni green tape
Sintering schedule for Ni electrodes
1 OC/min
RT
130 OC
1 OC/min
1 OC/min
1 OC/min
5 OC/min
230 OC
400 OC
800OC
130 OC
230 OC
400 OC
800 OC
RT
1 h
3 h
5 h
1 h
Nitrogen
Hydrogen
Flow chart for LSC Coated Ni electrode preparation
La, Sr, Co-Acetates Dist. Water
Stirring at 80o C
Ethylene Glycol
Stirring
Gel
Drying in Vacuum at 90o C
Sintering at 900o C in Air
Citric Acid
Ni Electrodes
XRD Patterns of La0.8Sr0.2CoO3 at different temperatures
0 20 40 60
Inte
nsit
y (a
.u)
2-T heta (deg.)
(110
)
(211
)
(208
)
400o C500o C
600o C700o C800o C900o C
300o C
(012
)
(202
)
(024
)
(214
)(0
18)
(220
)
(104
)
SEM Pictures of La0.8Sr0.2CoO3 coated Ni electrode After Sintering at 900°C
Bare Ni Electrode LSC Coated Ni ElectrodeSintered at 900o C
LSC Coated Ni Electrode after immersion in molten carbonate
Melt for 200 hours
Magnification X 2000
Dissolution Behavior La0.8Sr0.2CoO3
coated Ni electrode at 650o C
0 45 90 135 180 225
Time (Hours)
0
10
20
30
40N
i (m
ole
frac
tion
) X 1
06
Ni from LSC coated Ni
Ni from NiO
0.00 0.05 0.10 0.15 0.20
Applied Current (A/cm2)
-0.005
0.015
0.035
0.055
0.075
Pola
riza
tion
(,
V)
650 C700 C750 C
Effect of Temperature on Polarization Performance of NiO
Polarization Behavior of Ni
Polarization Behavior of La0.8Sr0.2CoO3 coated Ni electrode
30 80 130
Applied Current (mA/cm2)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
Ove
r P
oten
tial
(
)
650700750
0.75 1.55 2.35 3.15 3.95
Real Z
0.0
0.6
1.2
1.8
2.4-I
mag
inar
y Z
650 C700 C750 C
Comparison of Impedance response of NiO at different temperatures at
100 mV applied polarization potentials
Comparison of Impedance Behavior of Ni
EIS response for La0.8Sr0.2CoO3 coated Ni electrode at 650°C
1 2 3
Real Z' ( )
-0.1
0.4
0.9
1.4
1.9
2.4
2.9
-Im
agin
ary
Z"
()
0:60:162.5:60:1610:60:1620:60:1630:60:1645:60:1660:60:16
Increasing [CO2]
0.7 1.2 1.7 2.2 2.7
Real Z' ( )
-0.10
0.44
0.98
1.52
2.06
2.60
-Im
agin
ary
Z"
()
33:60:033:60:2.533:60:7.533:60:1533:60:22.533:60:30
Increasing [O2]
EIS response for La0.8Sr0.2CoO3 coated Ni electrode at 700°C
0.6 1.1 1.6 2.1Real Z' (
-0.1
0.4
0.9
1.4
1.9
-Im
agin
ary
Z"
(
33:60:033:60:2.533:60:7.533:60:1533:60:22.533:60:30
Incre asing [O 2]
0.5 1.0 1.5 2.0 2.5
Real Z'( )
-0.10
0.42
0.94
1.46
1.98
2.50
-Im
agin
ary
Z"(
)
Increasing [CO2]
0:60:162.5:60:1610:60:1620:60:1630:60:1645:60:1660:60:16
EIS response for La0.8Sr0.2CoO3 coated Ni electrode at 750°C
0.8 1.1 1.4Real Z' ()
-0.1
0.4
0.9
1.4
-Im
ag
ina
ry Z
" (
)
33:60:033:60:2.533:60:7.533:60:1533:60:22.533:60:30
Incre asing [O 2]
0.5 1.0 1.5 2.0 2.5
Real Z" ( )
-0.10
0.44
0.98
1.52
2.06
2.60
-Im
agin
ary
Z"
()
0:60:162.5:60:1610:60:1620:60:1630:60:1645:60:1660:60:16
Increasing [CO2]
0 1 2 3 4 5
Real Z' ()
-1
0
1
2
3
4
-Im
agin
ary
Z"
((
)
5:20:3216:20:3230:20:3240:20:3260:20:32
Increasing [O 2]
EIS response of La0.8Sr0.2CoO3 coated Ni electrode in Full Cell at 650°C
0 1 2 3Real Z' ()
-Im
agin
ary
Z"
()
Increasing [CO 2]
1.0
1.5
2.0
2.5
3.0
3.5
1.0
1.5
2.0
2.5
3.0
3.50:20:1616:20:1632:20:1664:20:16100:20:16
Conclusions
Rate of dissolution of Ni decreased significantly after La0.8Sr0.2CoO3 coating.The observed increase in polarization may be due to the decrease in porosity and change in surface morphology.La0.8Sr0.2CoO3 coated nickel oxides offer better
stability in MCFC cathode environment.
Financial sponsors - Dept of Energy,
National Energy Technology Laboratory
Acknowledgements
