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Prof. Guntae KimUlsan National Institute of Science and Technology (UNIST)
School of Energy and Chemical Engineering, S. Korea
Improving the Performance of Ceramic Anode by Exsolved Catalyst Nanoparticles in Solid
Oxide Fuel Cells
Curtin-UQ Workshop onNanostructured Electromaterials for Energy
2016. 1. 18.
Contents
1. Introduction
2. SOFC layered perovskite anode
3. Self decorated catalyst by Ex‐solution
4. Conclusions
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1. Introduction
Fuel Cell Choice
Fuel cells offer higher efficiency across a wide range of system size. Solid Oxide Fuel Cells (SOFCs) are well‐suited to large scale applications.
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Based on the electrolyte materials, each fuel cell has different operating conditions, power generating efficiency.
Type of Fuel Cells
1000 oC
500 oC
100 oC
700-1000 oCSolid oxide
type(SOFC)
Stabilizedzirconia
(Ceramic)45-65 %
Operating temperature
Type of Fuel cell Electrolyte
Power GenerationEfficiency
~650 oCMolten
carbonate type(MCFC)
Molten carbonate 45-50 %
~200 oCPhosphoric-acid type(PAFC)
Phosphoric acid 35-42%
Room Temp. to 90 oC
Polymer electrolyte
type(PEMFC)
Ion exchange membrane 35-40 %
Centralized power generation
Black out Social conflictHigh Cost and Danger
Industrial loss from black out
Industry fields Amount of loss
Mobile phone $41,000/hour
Credit card $2,580,00/hour
Financial business $6,480,000/hour
Ref. Journal of mechine
Substation Substation Pole transformer
77‐22 kV154‐77 kV765‐154 kV 220 V
Imbalance of Energy supply → high voltage, long distance transmission network
Risk regulatory cost
: $ 43 billion
Construction Cost (1GW)
: $ 3 billion
Radioactive waste cost
: $165 billion
Transmission and Distribution loss factor : 4.02 ~ 11.38 %
Why develop the fuel cell?
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Off the Grid Short period of construction Combined power generation
10
5
3
1
0 5 10
Construction period
Distributed power sources LNG Coal Nuclear
[unit : year]
Green energy
Direct Energy supply → Transmission network is not required → Cheap, Safe, and Eco‐friendly
Distributed power generation
Why develop the fuel cell?
Application of Fuel Cells
Bloom Energy, US
Simens, US
Kyocera, Japan Topsoe, Denmark
Hyundai Motors, Korea
AMI, US Sub‐battery for iphone
Delphi & BMW, US
Power generating type
Portable type
Mobile type
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2014. 7. 24GE Threatens to Enter Fuel Cell Market,
Compete With Bloom
General Electric(GE) announced that it is initiatingan entrepreneurial effort to commercialize its solidoxide fuel cell (SOFC) technology for megawatt-scale stationary power applications.
GE has claimed a recent fuel cell "breakthrough"with an efficiency of 65 percent and an overallefficiency of up to 95 percent when waste heat iscaptured.
GE plans to build a pilot plant and developmentfacility near Saratoga Springs, New York. GE will testa 50 kilowatt system at Hudson Valley CommunityCollege’s TEC-SMART facility next door.
The GE Conglomerate had $146 billion in revenuelast year.
Status of Fuel Cell market in USA
Status of Fuel Cell market in USA & Japan
Softbank-bloom energy Japan :$10M In Fukuoka, Softbank building, 200kw unit Efficiency: 52%, fuel: city gas
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Status of Fuel Cell market in Japan
2012.04
ENE-FARM
Operation tem.: 700-750oC, efficiency: 46.5%
Status of Fuel Cell market in Japan
Cell stack cartridge
2014.12
Price : 3 million dollars (including setting cost) 1.5 million dollars (only SOFC + turbine system,
excluding setting cost)
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Status of Fuel Cell market in Korea
2012. 06
LG buys controlling stake in Rolls-Royce fuel cell business.
Status of Fuel Cell market in Korea
5kW SOFC‐Engine Hybrid System
Status of performance, key characterizations
Technology : Solid Oxide Fuel Cell
Basic concepts (type of cell, stack configuration, core components)
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Basic principle of Solid Oxide Fuel Cells (SOFCs)
Direct conversion of fuel into electricity High efficiency Environmentally friendly Fuel flexibility (any hydrocarbon)
Advantages
Electrochemical Reactor which converts chemical energy directly into electrical energy
Cathode: Oxygen from the air is reducedO2 + 4e
‐ 2O2‐
Anode: Oxidation of fuelH2 + O
2‐ H2O + 2e‐
Conventional SOFCs use H2 or mixtures of H2 and CO
• Internal steam reforming of CH4
• External reforming of higher
hydrocarbons
Oxy‐reforming reduces
efficiency by ~30% Fuels : H2, CH4, C3H8, JP8, diesel etc.
2. SOFC layered perovksite anode:PrBaMn2O5+d
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Disadvantage of H2 fuel
1. Expensive & dependence on fossil fuels 2. Storage
4. Highly Flammable3. Not easy to replace existing infrastructure
Super‐light hydrogen is hard to transport in a reasonable fashion.
Hydrogen in itself is a very powerful source of fuel. It’s highly inflammable.
There is no existing infrastructure in place to accommodate hydrogen as a fuel source for the average motorist.
While widely available, hydrogen is expensive. Other non‐renewable sources such as coal, oil and natural gas are needed to separate it from oxygen.
Need to using direct hydrocarbon
for SOFC
What issue? Conventional Anode Material
1. Low carbon coking tolerance
2. Sensitive to sulfur in the fuel3. Anodes cannot tolerate re‐oxidation (Ni NiO Ni)
Traditional SOFC use Ni‐based anodes:
Conventional anode material : Ni‐YSZ cermet
High electronic conductivity Excellent activity for clean reformed fuels Chemically and physically compatible with YSZ electrolyte
(X)
Developing new anode materials instead of Ni‐based anode
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Requirements of Anode Material
+Good Tolerance Carbon coking Sulfur poisoning
Electrical ConductivityHigh electrical
conductivity in reducing condition
Good SOFCAnode
Material
Catalytic Activity Operation at lower temperature Enhance active site density
“For Direct Hydrocarbon Fuels”
Materials Compatibility Thermal expansion Solid State Reaction
Properties of layered PrBaMn2O5+d (PBMO)
Oxygen Deficient Layered
Perovskite as Efficient and
Stable Anode :
PBMO
S. Sengodan, G. Kim*, Nature Materials (2015) 14, 205
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Layered perovskite structure
Simple perovskite oxide (ABO3‐d)
A : La, Sr, Ca, and Ba, etc. Coordinated to twelve oxygen atoms
B : Ti, Cr, Ni, Fe, Co, and Mn, etc. Coordinated to six oxygen atoms.
A : La, Pr, Nd, Sm, Gd
A’ : Ba, Sr
B : Co, Fe, Mn, Cu
Double structure Significant size difference between
the large Ba and the smaller Ln.
A
B
O
A
A'
BOO
Double perovskite oxide (AA’B2O5+d)
Recently, new cathode materials have gotten an attention.Ordered perovskite structure, PrBaCo2O5+
Ordered perovskite is faster oxygen kinetics than disorder perovskite
Comparison of diffusion coefficient
G. Kim, J. Mater. Chem., v.17, p2500‐2505 (2007)
Comparison of surface exchange coefficient
Cation ordered perovskite structure?
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Mobileoxygen
Ln
Ba
Co
Lattice Oxygen
Layered perovskite structure (AA’B2O5+)
Size difference between the large Ba
cation and the smaller Ln cation
Layered perovskite structure
Simple perovskite (ABO3‐Layered perovskite (AA’B2O5+
2. SOFC ‐ Layered perovskite papers since 2006
Layered perovskite papers
La: G.Kim, Solid State Ionics, 177, 1461 (2006), G. Kim, Electrochem. Solid‐State Lett., 11, B16 (2008), G. Kim, Chem.Mater., 22, 776 (2010), S. Choi, G. Kim Electrochem. Commun., 32, 5 (2013)
Pr: G.Kim, Appl. Phys. Lett., 88, 024103 (2006), G. Kim, Appl. Phys. Lett., 90, 212111 (2007), G. Kim, J. Mater. Chem., 17,2500 (2007), S. Park, G. Kim, ECS Electrochemistry Letters, 1 (5), F29 (2012), S. Choi, G. Kim J. Power Sources 2011, 10(2012), S. Park, G. Kim RSC Advances, 4, 1775 (2014) S. Park, G. Kim Electrochim. Acta, 125, 683 (2014), S. Choi, G. KimJ. Mater. Chem. A, 3, 6088 (2015)
Nd: S. Yoo, G. Kim J. Mater. Chem., 21, 439 (2011), S. Yoo, G. Kim J. Electrochem. Soc., 158 (6) B632 (2011), S. Yoo, G.Kim Electrochimica Acta, 100, 44 (2013), J. Kim, G. Kim J. Mater. Chem. A, 1, 515 (2013), J. Kim, G. Kim Electrochim.Acta, 112, 712 (2013), C. Kim, G. Kim Int. J. Hydrogen Energy, 39, 20812 (2014), J. Kim, G. Kim ChemSusChem, 7, 1669(2014)
Sm: A. Jun, G. Kim Int. J. Hydrogen Energy, 27, 18381 (2012), A. Jun, G. Kim Phys.Chem.Chem.Phys., 15, 19906 (2013),Y‐W. Ju, G. Kim, J. Electrochem. Soc., 161 (5) F668 (2014), A. Jun, G. Kim Int. J. Hydrogen Energy, 39, 20791 (2014)
Gd: J. Kim, G. Kim J. Am. Ceram. Soc., 97, 651 (2014)
O. Kwon, G. Kim*, Angewandte chemie Int. Ed on press (2015) S. Sengodan, G. Kim*, Nature Materials 14, 205 (2015) S. Yoo, G. Kim*, Angewandte chemie Int. Ed. 53, 13064 (2014) ‐ Cover page S. Choi, G. Kim*, Scientific Reports 3, 2426 (2013)
Search the number of publication for DP: ~ 400Including the application of SOFC, SOE, H+‐SOFC
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Fabrication of fuel cell
LSGM based electrolyte supported cell
PBMO anode
LDC buffer layer
LSGM electrolyte
Fuel cell test conditions
LSGM : La0.9Sr0.1Ga0.8Mg0.2O3‐δ
Anode : PrBaMn2O5+ (PBMO)
Cathode : NdBa0.5Sr0.5Co1.5Fe0.5O5+ (NBSCF)
Structural Property – A site ordering synthesis concept
Exothermic peak (*) Phase change occurs upon heating at 400 oC in reducing condition.
Air synthesis PBMO
Layered PBMO
Air synthesis PBMO
Layered PBMO
Phase changes from Simple to
Layered Perovskite
Principle of the approach to prepare A‐site layered perovskite PBMO
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Structure Property – TEM analysis
Surface area 2.42 m2/g
Surface area 5.32 m2/g
S. Sengodan, G. Kim*, Nature Materials 14, 205 (2015)
2. SOFC Electrode‐Anode (PrBaMn2O5+)
Cell performance is almost constant without degradation for 500 hours in C3H8
PBMO anode High electrical conductivity in H2
Excellent redox property Good carbon coking tolerance
Highly efficient and stable anode material
S. Sengodan, G. Kim*, Nature Materials 14, 205 (2015)
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3. Self decorated catalyst by Ex‐solution
Ex‐solution
Metal nanoparticles ex‐solution from the perovskite oxide host in a reducing environment.
The ex‐solved metal nanoparticles with small size may act as high active sites for oxidation reaction of hydrocarbon during the cell operation
3. Ex‐solution
Y. Nishihata, et al. Nature. 2002, 418, 164.D. Neagu, et al. Nat. Chem. 2013, 5, 916–23.D. Neagu, et al. Nat. Commun. 2015, 6, 8120
DAIHATSU‐TOYOTA COLLABORATIVE RESEARCH
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3. Ex‐solution – layered perovskite_PBM??
Thickness of LSGM : 250 m Qualitative analysis : XRD, SEM, TEM
Quantitative analysis : DFT
Electrochemical performance : Impedance, Power density
PLD : PBMO and PBMCO samples deposit on the Al2O3 film.
LSGM (electrolyte)
NBSCF50-GDC (cathode)
PBMO or PBMCO (anode)
LDC (buffer layer)
3. Ex‐solution – SEM of bulk electrode, Mn vs. Co
(a,b) the surface of the before reduced samples is smooth without any nanoparticles on the surface. (c,d) some small nanoparticles of 20~50 nm diameter are observed on the surface of reduced samples
Pr0.5Ba0.5MnO3 Pr0.5Ba0.5Mn0.85Co0.15O3
PrBaMn2O5+ PrBaMn1.7Co0.3O5+
After Reduction in H2
Co
MnO
PrBaMn2O5+
PrBaMn1.7Co0.3O5+
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3. PLD thin film_Ex‐solution – TEM
PBMO and PBMCO films on Al2O3 were reduced at 800 oC for 10 min
The lattice constants of the MnO and Co correspond to each XRD data
PBMO
PBMCO
MnO
Co
In situ growth of nanoparticles through control of non‐stoichiometry
PBMO
PBMCO
D. Neagu, et al. Nat. Chem. 2013, 5, 916–23.
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3. Ex‐solution – DFT Calculation
(a) Schematic of B‐metal segregation(b) Schematic of oxygen vacancy formation on the surfaces
The co‐segregation energies are ‐0.47 and ‐0.55eV for PBMO and PBMCO, respectively‐ Co is more favorable to segregate towards the surface than Mn
The oxygen vacancy formation energies are 2.97 eV and 2.46 eV for PBMO and PBMCO, respectively, in the surface.
2.97 eV 2.46 eV
PBMO PBMCO PBMO PBMCO
Pr
Ba
O
Mn Co
Collaboration with Prof. J. Hahn, University of Seoul
‐0.47 eV ‐0.55 eV
Segregation energy Oxygen vacancy formation energy
3. Ex‐solution – DFT Calculation
Side views of (a) PBMO and (b) PBMCO on the surface, respectively.
The most stable sites of oxygen vacancy formation in PBMO and PBMCO are both near the surfaces. Thus, oxygen vacancy formed in the bulk prefers to be segregated out to the surfaces.
The oxygen vacancy are more preferentially formed in PBMCO than in PBMO at each layer.‐ the principle of exsolution
PBMO PBMCO
1layer 2.97 2.46
3layer 3.08 2.95
4layer 3.72 3.55
5layer 3.45 3.35
Pr
Ba
O
Mn Co
PBMO PBMCO
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3. Ex‐solution – electrochemical properties
Ceramic anode Electrolyte Thickness (μm)
Temperature (oC)
Maximum Power density (W cm-2)
Layered PBMO 250 800 0.66
Layered PBMCO 250 800 1.15
Fabrication Technique : screen print on LSGM supportedAnode : Ceramic anodeCathode : NdBa0.5Sr0.5Co1.5Fe0.5O5+‐GDC composite
1.15 W cm‐2
@ 800oC in H2
No external Catalysts !!
0.66 W cm‐2
@ 800oC in H2
• A PrBaMn2O5+ demonstrates superior SOFC ceramic anodeperformance and stability in various fuels.
• Layered anodes exhibit high electrical conductivity,excellent redox and coking tolerance.
• On the basis of the number of good properties, layeredPBMO is an attractive anode material for SOFC applications.
Anode material
Conclusion
• The unique or exclusive structural phase transition inperovskite ceramic anode potentially offers a newapproach to produce nanoparticle decorated perovskitesurface for next generation electrodes for SOFCs.
• No need external catalysts
Ex‐solution
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Prof. Jeeyoung Shin (Dong‐Eui Univ.)
Dr. Seonyoung YooDr. Sivaprakash SengodanDr. Sihyuk ChoiAreum JunSeonhye ParkJunyoung KimOh‐hun GwonSeona KimChangmin KimOh‐hoon KwonChaehyun LimDongwhi JungSangwook JooChanseok Kim
Prof. Young‐wan Ju
Many thanks to…
http://gunslab.unist.ac.kr
Thank you for your attention