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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