nano-engineering strategies toward advanced …2019/04/22 · promising non-precious metal oxide...

국제수소포럼 2019 (2019. 5. 9 ~ 10)

Nano-engineering Strategies toward Advanced Material

Architectures for Efficient Energy Conversion and Storage(고효율 에너지변환시스템 구현을 위한 신소재 나노에지니어링 전략)

전북대학교

남 기 석 (Kee Suk Nahm )

Chonbuk National University

Jeonju 54896, Republic of Korea

Tel: +82-63-270-2311/Fax: +82-63-270-2311

E-mail: [email protected]

mailto:[email protected]

서론- Why hydrogen energy?

- Why nano-engineering strategy in energy conversion system?

- What electrochemical reactions in energy conversion system?

연구동기- Why Lithium air battery for energy conversion system?

- What issues for commercialization?

연구전략- 3D nanostructures Synthesis -> electrochemical characterization

-> system performance evaluation

연구결과- MnO2 : promising non-precious metal oxide catalysts in air electrode

- MnO2/RuO2 bifunctional catalyst

- Perovskite La0.6 Sr0.4 CoO3-8(LSC) oxide

결과Effective catalyst materials

2

수소경제 활성화 로드맵 비전

2018 2022 2040

수소차 1,800 81,000 6,200,000

연료전지발전용 307MW 1.5GW 15GW

가정•건물용 7MW 50MW 2.1GW

수소공급(Ton/년)

130,000 470,000 >5,260,000

수소가격(원/kg)

- 6,000 3000

산업통상자원부 보도자료 (2019. 1. 17)

6

- Hydrogen exists on Earth in the form of compounds (hydrocarbons, H2O etc.).

- Reforming of Fossil Fuels => generate Global warming

- Thermochemical water-splitting using Nuclear energy, Photolysis & etc(electrolysis) using Renewable energy => low economic feasibility

※ Electrolysis: three times higher expensive than reforming

Energy (Entalphy, Entrophy, & Gibbs Free energies) necessary to decompose 1 mole of water molecueinto 1 mole of H2 and ½ mole of O2) at 25oC and standard conditionj

7

수소생산

[1] 남기석, “수소에너지개론”, 도서출판 어화 (2007) [2] 남기석,”수소연료전지 HANDBOOK”, 성안당 (2011)

물의 전기분해

재생에너지로부터 수소생산

Electrodes Catalyst could greatly improve the performance of

hydrogen production (electrolysis, photolysis, etc.) using renewable

energy, resulting in the decrease of H2 production cost

H2O + electricity → H2 + 1/2O2

물의 광분해

H2O + h+/e- → H2 + 1/2O2

( )

CdS, TiO2, SiC etc.

Decoration of TiO2 photocatalyst

with Noble metal (Pt, Au, Pd, Rh, Ni,

Cu and Ag) and transitional metal

ions (Cr, Mn, Fe, Co, Ni, and Cu)

8

[1] Ke Wang et. al, ACS Appl. Mater. Interfaces, 2016, 8 (5), pp 2910–2916

[2] Jiaguo Yu, J. Phys. Chem. C 2010, 114, 13118–13125

[3] Taehwan Hyeon et. al., Nature Materials, 22 April 2019.

촉매 미세구조가 수소생산에 미치는 영향

CoTe2 NDs/CoTe2 NTs CoTe NSs/CoTe2 NTs

(nanodendrite/NT) (nanosheet/NT)

전기분해 [1]

* Taeghwan Hyeon et al., , Nature Materials, 22 April 2019 [3]

Photocatalytic Water Splitting over NS4: Pt/F/TiO2 Nanosheets & NP: Pt/TiO2 Nanoparticle

광분해 [2]

9

https://www.nature.com/articles/s41563-019-0344-1#auth-13https://www.nature.com/articles/s41563-019-0344-1#article-info

수소저장

FuelsVolumetric Energy Density Weight Energy Density

H2 gas

Natural gas

H2 liquid

Gasoline

[Comparison of caloric value between hydrogen and other fuels]

- Hydrogen has a greater weight energy

density than other fuels.

- But volumetric energy density is lower

than other fuels. (~1/3 of natural gas and

1/3000 of gasoline.)

- So, how to store and transport H2 while

maintaining higher volumetric energy

density is a big technical challenge.

[3] K.S.Nahm et. al, Int. J. Hydrogen Energy, 17(5), 333-338(1992).


[3]

[4]

10

수소 저장 방법과 저장밀도의 비교


[6] K.S.Nahm et. al, Chemical Physics Letter, 441(4-6), 261-267(2007).

[7] K.S.Nahm et. al, Carbon, 47(6), 1585-1591(2009)

20.08554 148.41316 1096.633160

1

2

3

Hy

dro

gen

sto

rag

e (w

t%)

Time (s)

40atm, 25o

C, 2.70wt%

40atm, 30o

C, 2.95wt%

40atm, 35o

C, 2.90wt%

Pt-CNT (10mA x 50s)

1 20.08554 403.42879 8103.083930

1

2

3

Hy

dro

gen

Sto

ra

ge (

wt%

)

3.2 wt%

3.1wt%

3.2wt%

Pt-Pd CNT (5nm, 3nm) 33 ~ 34atm, 25oC

Time (s)

[5]

[6]

[7]

cata

lyst

s

H2 R

evers

ibility &

acc

ess

ibility

11

지속가능사회를 위한 수소도입 시나리오

[1] 남기석, “수소에너지개론”, 도서출판 어화 (2007) [2] 남기석,”수소연료전지 HANDBOOK”, 성안당 (2011) 12

PHOTOLYSIS

Fuel Cell ELECTRICITY STORAGE

e-

H2 Energy conversion systems: water electrolysis and photolysis, H2 storage, fuel cells, metal–air batteries, etc.

[1] Zu.tte et al., “Hydrogen as a Future Energy Carrier, Wiley-VCH, Weinheim,

Germany, 2008 13

수소에너지변환 사이클

∼ 일연의 전기화학반응 (electrochemical reactions)• oxygen reduction reaction (ORR)• hydrogen oxidation reaction (HOR)• hydrogen evolution reaction (HER)• oxygen evolution reaction (OER)

The polarization curves for two pairs of the key energy-relatedelectrochemical reactions and their overall reaction equations. [1]

[1] Yan Jiao et al., Chem. Soc. Rev., 2015, 44, 2060--2086

Therefore,

these reactions are

generally catalyzed by

precious metals (Pt, Ir and

Ru-based catalysts) to

achieve favorable reaction

kinetics for practical

applications.

The kinetics of two-electron

transfer in the hydrogen-

involving reactions, HER and

HOR, is facile.

A multistep proton-coupled

electron transfer in oxygen-involving reactions, ORR and OER, is kinetically sluggish.

14

Transition metal oxide

catalysts (MnO2,

RuO2, Perovskite..)

에너지변환시스템

Discharg 𝐎𝐑𝐑 :𝑶𝟐 + 𝟐𝑳𝒊+ + 𝟐𝒆− → 𝑳𝒊𝟐𝑶𝟐(s)

Charge (OER): 𝑳𝒊𝟐𝑶𝟐(𝒔) → 𝑶𝟐 + 𝟐𝑳𝒊+ + 𝟐𝒆−

Difference?

𝑳𝒊𝑴𝒏𝑶𝟐 ↔ 𝑳𝒊𝑴 𝟏 − 𝒙𝑶𝟐 + 𝒙𝟐𝑳𝒊

+ + 𝒙𝟐𝒆−𝑪 + 𝒙𝑳𝒊+ + 𝒙𝒆− ↔ 𝑳𝒊𝒙𝑪

charge

discharge

Similarity?

리튬-공기전지(Lithium Air Battery)의 작동 원리

𝟏

𝟐𝑶𝟐 + 𝟐𝑯

+ + 𝟐𝒆− → 𝑯𝟐𝑶Cathode:

Cathode:

15

※ 전형적인 ORR과 OER 반응으로작동하는 에너지변환시스템

LiCoO2 (1)

[8]. Kee Suk Nahm et. all., Solid State Ionics, 109(3-4), 285-294 (1998).

[9]. Kee Suk Nahm et. all., Journal of the Electrochemical Society, 153(2), A390-A395 (2006).

[10]. Kee Suk Nahm et. all., J Solid State Electrochemistry, 19, 1501–150 (2015)

Li[Li1/5Ni1/10Co1/5Mn1/2]O2 (2)

Li-air (3)

Charge/Discharge curves 전기에너지 저장기술 발전 방향

[8]

[9]

[10]

16

𝑶𝑹𝑹: 𝑶𝟐 + 𝟐𝑳𝒊+ + 𝟐𝒆− → 𝑳𝒊𝟐𝑶𝟐(s)

𝑶𝑬𝑹: 𝑳𝒊𝟐𝑶𝟐 𝒔 → 𝑶𝟐 + 𝟐𝑳𝒊+ + 𝟐𝒆−

charge

연구동기: 리튬-공기전지에서 해결해야 할 기술

Main Issue

17

Our work …. Nano-engineering technology to control 3D-nanostructuresTo find effective bifunctional catalysts for ORR&OER.

Effect of nitrogen doping & ballmilling techniques of Carbon materials

on ORR electrocatalytic activity [11]

3D-MnO2 nanostructures

- Different phases (α & δ) of MnO2 nanostructures

- Pd/α- MnO2 [12]

- MnO2/N-GNF [13]

α- MnO2/RuO2 Bifuctional electrocatalyt

Perovskite La0.6 Sr0.4 CoO3-8 oxides

~ excellent catalyst for OER

- Surface modifications such as ball milling,

- Three dimensional techniques

- Pd/ Perovskite oxides

- Synthesis and electrocatalytic activity -

[11]. Kee Suk Nahm et. al., Applied Catalysis B: Environmental 147 (2014) 633–641

[12] Kee Suk Nahm et. al., Journal of Solid State Electrochem (2015) 19:1501–1509

[13]. Kee Suk Nahm et.al., Electrochimica Acta, 157, (2015) 299–306 18

1. Structural and chemical composition characterization :

XRD, FESEM, HRTEM, BET, XPS, IR, Raman,,,,,

-> morphology &crystal structures, surface states, chemical composition, etc.

2. Electrochemical characterization : - electrochemical reaction identification, onset potential, limiting current, kinetic

current, ESA, half wave potential, Tafel plot, impedance = electrocatalytic activity

Glove box Cell testSwagelok™ type cell

3. Battery characterization: Discharge and Charge capacities, potential gap, cyclibility,,,

- Working electrode (WE) : (Catalysts/C))

- Reference electrode (RE) : Hg/HgO

- Counter electrode (CE) : Pt

- Electrolyte : 0.1M KOH saturated with O2

Three electrode cell

- Chronoamperometry- Cyclic Voltammetry

- Linear Sweep Voltammetry

- Chronopotentiometry

- Impedance

potentiostat

- chathode : (Catalysts/C))

- Anode : Li metal

- Electrolyte : Li+ organic solvent(LiTFSI/ TEGDME)

전극재료 스크린 전략

19

Our work 1….

17

Effect of nitrogen doping of Carbon materials on ORR electrocatalytic activity

3D-MnO2 nanostructures


- Pd/α- MnO2- MnO2/N-GNF

α- MnO2/RuO2 bifunctional electrocatalyst






Figure. SEM images of MnO2 (temperature dependent morphology after 12 hours of reaction).

1. Nano-engineering Application in Synthesis of 3D-MnO2Nanostructure Catalyst

18

Figure. XRD patterns of MnO2 grown as a

function of reaction temperature for 12 hours.

Figure. XRD peak position analysis of

temperature dependent samples.

19

Formation mechanism of MnO2 nanostructures

[14] Kee Suk Nahm et. al., Science of Advanced

Materials, Vol. 6, pp. 2712–2723, 201420

Charge-discharge capacities of urchin shaped α–MnO2 and δ–MnO2layered birnessite

Charge/Discharge curves for LiCoO2

Figure. Charge discharge profiles of urchin shaped α–MnO2 and δ–MnO2 layered birnessite.

21

1.2 V

Mass activity

Crystallographic form Size/Å

α (1X1) (2X2) 1.89, 4.6

0.73nm

O

Mn

δ–MnO2α–MnO2

Crystallographic structure study of urchin shaped α–MnO2 and δ–MnO2layered birnessite

Figure. Crystallographic structure of δ-MnO2.

Figure. Crystallographic structure of α-MnO2.

22

[15] Kee Suk Nahm et. al., RSC Adv., 2

014, 4, 8973

Volcano plots for different metal surfaces

ORR activity for a range of pure metals plotted against O* adsorption energy

Activity trends for OER as a function of DGO* DGOH* for rutile and anatase oxides

[1] Yan Jiao et al., Chem. Soc. Rev., 2015, 44, 2060-2086

Discharg 𝐎𝐑𝐑 :𝑶𝟐 + 𝟐𝑳𝒊+ + 𝟐𝒆− → 𝑳𝒊𝟐𝑶𝟐(s)

Charge (OER) : 𝑳𝒊𝟐𝑶𝟐(𝒔) → 𝑶𝟐 + 𝟐𝑳𝒊+ + 𝟐𝒆−

Lithium-Air Batteryα-MnO2RuO2

Bifunctional Electrocatalytic activity for ORR and OER

23

Our work 2….

24


MnO2 nanostructures



α- MnO2/RuO2 Bifunctional electrocatalyst






2. Nano-engineering Application in Synthesis of α-MnO2/RuO2(82:18) Mixed

Oxide Nanostructure Catalyst

Figure. The α–MnO2/RuO2 mixed oxides are formed in the shape of sea urchin nanostructures as we observed from α–

MnO2 sea urchin nanostructures.

25

[16] Kee Suk Nahm et.al., Journal of The Electrochemical Society, 163 (2) A244-A250 (2016)

BET analysisEDX analysisXRD analysis

26

TEM image and EDS mapping

Figure. The TEM–EDS mapping exhibits a uniform distribution of Mn, Ru, and O elements throughout the sea urchin nanostructures.

27

음극(Anode) LSV - OER Curves

α–MnO2/RuO2

Linear Sweep Voltammetry

Figure. OER curves measured in the cathodic reduction region (−0.8∼0.3V vs. Hg/HgO) and anodic potential up to 1.0 V vs. Hg/HgO in O2 saturated 0.1 M KOH at a scan rate of 5 mV s−1 and 1600 rpm.

280.4 0.6 0.8 1.00.0

-0.5

-1.0

-1.5

-2.0

-2.5

-3.0

-3.5

-4.0

Cu

rre

nt(

mA

)

Voltage(V vs. Hg/HgO)

KB

Pt/C

a-MnO2

MnO2 only

양극(Cathode) LSV - ORR Curves

Linear Sweep Voltammetry

α–MnO2/RuO2

Figure. ORR curves measured in the cathodic reduction region (−0.8∼0.3V vs. Hg/HgO) and anodic potential up to 1.0 V vs. Hg/HgO in O2 saturated 0.1 M KOH at a scan rate of 5 mV s−1 and 1600 rpm.

29-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

-0.2

Voltage(V vs. Hg/HgO)

Curr

ent(

mA

)

KB

Pt/C

a-MnO2

MnO2 only

Figure 4. LSV curves measured in the cathodic reduction region (−0.8∼0.3V vs. Hg/HgO) and anodic potential up to 1.0 V vs. Hg/HgO in O2 saturated 0.1 M KOH at a scan rate of 5 mV s−1 and 1600 rpm for ORR and OER.

30

Four different compositions of α-MnO2/RuO2 Mixed Oxides Nanostructure

α–MnO2/RuO2(82:18) α–MnO2/RuO2(75:25)

α–MnO2/RuO2(69:31)α–MnO2/RuO2(50:50)

Figure. Four different a–MnO2/RuO2 hybrids with (82, 18),(75:25), (69:31) and (50:50).

31[17] Kee Suk Nahm et.al., Electrochimica Acta, 212, 701–709 (2016)

Figure. (a) The first cycle charge–discharge capacities, (b) cycling profiles of a–MnO2/RuO2 hybrids catalyzed Li–

O2 battery measured at 0.1 mAcm2, (c) Charge–discharge potentials as a function of cycle number and (d) limited

capacity cycling as a function of cycle number. The battery performance test is well coincided with the electrochemical characterization (ORR & OER) results.

0.7 V

32

Figure. (a) XRD patterns and (b) SEM images of a–MnO2/RuO2 hybrids catalyzed air

cathodes measured (i) pristine, (ii) after discharge and (iii) after charge for post characterization.

Post Characterization

The α–MnO2/RuO2 exhibits rather stable specific capacities with low overpotential after

cyclings. a–MnO2/RuO2 (75:25) is the most efficient catalyst compared to other

investigated catalysts. (discharge capacity: 8250 mAh/g, overpotential: 0.7V). 33

Our work 3….

34


MnO2 nanostructures



α- MnO2/RuO2 Bifunctional electrocatalyt






Figure. FESEM images of LSC and TEM image of LSC & ball milled LSC.

[18] Kee Suk Nahm et. al., RSC Advances, 5, 19190-19198(2015)

[19] Kee Suk Nahm et. al., Journal of The Electrochemical Society, 163 (2) A244-A250

(2016)

3. Synthesis of Perovskite La0.6 Sr0.4 CoO3-8(LSC) & and its Ball

Milling Effect on Electrocatalytic Activity for Lithium Air Battery

35

Figure. Oxygen electrode activities with the oxygen reduction and evolution reaction potential windows of the La0.6Sr0.4CoO3-δ perovskite catalysts in oxygen-saturated 0.1 M KOH solution at 1600 rpm with a scan rate of 5 mV s-1

Figure. Cyclic voltammogram of La0.6Sr0.4CoO3-δperovskite catalysts in O2 saturated 0.1 M KOH solution at 50 mV s-1.

Electrochemical Characterization

36

Figure. Mass and specific activities of the La0.6Sr0.4CoO3-δ perovskite catalysts obtained at 0.2,

0.25 and 0.3 V (vs. Hg/HgO; 0.1 M KOH) from ORR data.

37

Figure. First charge–discharge profiles of LSC catalyzed Li–O2 battery in comparison without catalyst. The 1st discharge curve of LSC1000 reached a maximum capacity of 4208 mA h/g with a flat discharge plateau at 2.75 V. BM LSC1000 showed a maximum first capacity of 4701 mA h/g.

This indicates Battery performance could be predicted only by electrochemical characterization in aqueous

electrolyte

The observation from battery performance test is well coincided with the electrochemical characterization (ORR & OER) results.

38

Figure. Cycle life efficiency of the lithium–air battery at a constant discharge capacity of

500 mAh/g for La0.6Sr0.4CoO3-δ perovskite catalysts, (a) discharge and (b) charge. Insets in

the figure shows the cycle number cells start to fade. As you can see, LSC1000 and ball

milled LSC1000 show higher cycle performance.

Surface area = 0.2 m2/g

39

Figure. SEM images of 3DOM La0.6Sr0.4CoO3d perovskites: (a) Powder LSC1000, (b) Pellet LSC650, (c) Pellet LSC1000, (d) Centrifuge LSC650, (e) Centrifuge LSC1000 and (f) PMMA template.

Enhanced electrocatalytic activity of three-dimensionally-ordered macroporous

La0.6Sr0.4CoO3_d perovskite oxide for Li–O2 battery application

[20] Kee Suk Nahm et. al., RSC Advances, 6, 32212–32219 (2016).

Three-dimensional perovskite La0.6Sr0.4CoO3d (3DOM LSC) structures show much higher surface area.

40

Figure. ORR and OER polarization curves of 3DOM La0.6Sr0.4CoO3-δ and KB in O2-saturated 0.1 M KOH solution at 5 mV/s.

Figure. Charge–discharge profiles of Powder LSC1000, Pellet LSC1000, Centrifuge LSC1000, and KB.

0.85V

41

Figure. Cycle performance of Powder LSC1000, Pellet LSC1000,

and Centrifuge LSC1000 catalysts under a specific capacity limit

of 500mA h g1 at 0.1 mA cm2 : (a) discharge and (b) charge.

[21] Kee Suk Nahm et. al., RSC Advances, 6, 32212–32219 (2016).

We found that the perovskite oxides show superior catalytic activities for both ORR and OER. The increase of

surface area and porosity by ball milling and 3D techniques is effective to enhance the Li-air battery performance.

42

The observation from battery performance test is well coincided with the electrochemical characterization (ORR

& OER) results.

This indicates Battery performance could be predicted only by

electrochemical characterization in aqueous electrolyte

결 과1. To show that nano-engineering strategy toward advanced material architectures is efficient to enhance the

efficiency of energy conversion and storage, non-precious 3D-nanostructure materials were fabricated and

characterized using various electrochemical techniques and battery performance tester.

2. It was identified that the electrode catalysts architecture using nano-engineering technology is efficient to

enhance the efficiency of ORR and OER bifunctional catalysts for energy conversion and storage.

3. It was found that Li-air battery performance could be predicted only by electrochemical characterization in

aqueous electrolyte.

4. We found that the bifunctional catalyst of α–MnO2/RuO2 (75:25) mixed oxides show the best battery

performance (highest discharge capacity, lower overpotential, and cycle capability).

CatalystDischarge Capacity

(mAh/g)

Charge Capacity

(mAh/g)V (V)=Ch.Pot-Dh. Pot

Dischrage cycle fading

(cycle) at 0.1 mAh/g

Charge cycle fading

(cycle) at 0.1 mAh/g

MnO2

α-MnO2 6125.5 6125.5 1.2 35cycle at 800 35cycle at 800

δ-MnO2 3674 3674 1.2 20cycle at 800 20cycle at 800

α-MnO2/N-GNF 2943 2907 1.5 50cycle at 500 50cycle at 500

Pd/ α-MnO2 8526 8526 1.035cycle at 500

20cycle at 800

35cycle at 500

20cycle at 800

Perovskite

La0.6Sr0.4CoO3

LSC1000 4208 3490 1.5 50cycle at 500 34cycle at 500

BM-LSC1000 4701 4000 1.1 53cycle at 500 38cycle at 500

Pellet 5316 4750 1.09 (at 1250 mA h g-1) 53cycle at 500 51cycle at 500

Centrifuge 6066 5530 0.85 (at 1250 mA h g-1) 60cycle at 500 54cycle at 500

α-MnO2/RuO2

82:18 5500 5000 1.2No fading to

50 cycle at 500

No fading to

50 cycle at 500

75:25 8250 7850 0.7 44cycle at 1000 40cycle at 1000

69:31 6150 6200 1.2 34cycle at 1000 40cycle at 1000

50:50 4650 4050 1.3 30cycle at 1000 40cycle at 1000 43

44

Question?

Thank you!

287쪽 975쪽

수소의 에너지로의 사용 가능성과 한계부터, 제조, 저장, 운송, 안전의 기술적인 정보와 수소경제 도입 시나리오에 이르기 까지 …..

대학 교육, 연구, 산업화에 이르기까지 필요한 수소연료전지 정보와 데이타 제공……

nano-engineering strategies toward advanced …2019/04/22 · promising non-precious metal oxide...

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