1

グラフェンから成る多孔体とその酸化特性

西原 洋知

Institute of Multidisciplinary Research for Advanced Materials, Tohoku University

第4回酸化グラフェン研究会, 熊本大学, 熊本,2015年6月26日, 招待講演

東北大学多元物質科学研究所

Hirotomo Nishiharanisihara@tagen.tohoku.ac.jp

C6

12.01

Carbon blackCarbon blackFullereneFullerene

Carbon nanotubeCarbon nanotube

GrapheneGraphene

・Very light, unlike metal.・Electrically conductive like metal.

・Durable against acid and base, unlike metal.・Very high tensile strength.・Structure variety.

Carbon materials

Structure variety of graphene enables various forms of carbon materials.Structure variety of graphene enables various forms of carbon materials.

GraphiteGraphite

Activated carbonsActivated carbons Carbon fibersCarbon fibers

Carbon materials for energy applications

Lithium-ion batteries (LIBs)Lithium-ion batteries (LIBs)

・Graphite・Graphite・Hard carbons・Hard carbons

Electric double-layer capacitors (EDLCs)Electric double-layer capacitors (EDLCs)

・Activated carbons・Activated carbons

Polymer electrolyte fuel cells (PEFCs)Polymer electrolyte fuel cells (PEFCs)

Hydrogen storageHydrogen storage

・Carbon black (Pt support)・Carbon black (Pt support)

CNT?Activated carbon?Graphene?

CNT?Activated carbon?Graphene?

・Carbon cloth (GDL)・Carbon cloth (GDL)Nanostructure control is a key to achieve high performance in these applications.Nanostructure control is a key to achieve high performance in these applications.

Activated carbonGraphite Carbon black

Specific surface area ≒0 m2/g 300～700 m2/g ～3000 m2/g

Crystallinity High Low

Oxidation resistance High LowConductivity High Low

Carbon materials used as electrodesCarbon materials used as electrodes

SupercapacitorsBulk reaction, LIBs PEFCs

応用を考える際、比表面積と酸化特性は極めて重要応用を考える際、比表面積と酸化特性は極めて重要

2

カーボン材料の比表面積と酸化特性

活性炭の構造

構成単位はグラフェン

両側の面積 ＝ 2627 m2/g

・活性炭の比表面積の上限・グラフェンの比表面積（と、よく言われる）

n枚積層すると、

・グラフェンの積層が少ないほど高比表面積・グラフェンの積層が少ないほど高比表面積

水処理用活性炭： ～1500 m2/gキャパシタ用活性炭：～2000 m2/g高性能活性炭：～3000 m2/g

エッジ：酸化や化学反応の起点

n2627

m2/g

ベーサル面：化学的に不活性

・酸化特性はエッジ面の量に依存・酸化特性はエッジ面の量に依存

フレーレン C60 グラフェン

0D

カーボンナノチューブ

2D

理論比表面積2625 m2/g 2627 m2/g直径約 1 nm 直径 1 ～ 3 nm

1460 ～1760 m2/g(外側のみ) (両側)(外側のみ)

実際の比表面積 ～0 m2/g ～700 m2/g～1000 m2/gD. N. Futaba, et al., Nat. Mater. 5 (2006) 987

M. D. Stoller, et al., Nano Lett. 8 (2008) 3498

1D分子構造

グラフェン構造体はファンデアワールス力により極めて凝集し易いため、理論比表面積を実現するのは至難

グラフェン構造体はファンデアワールス力により極めて凝集し易いため、理論比表面積を実現するのは至難

fcc結晶 バンドル 積層

実際の材料の構造

グラフェン構造体の比表面積

高表面積化の方法①グラフェンベーサル面の露出

Schwartz P surfaceT. Lenosky Nature, (1992)S. J. Townsend Phys. Rev. Lett., (1992)

Pillared graphiteK. Georgios, Nano Lett., (2008)

グラフェン

？

高比表面積化のためには、グラフェンの両面を露出させる3次元骨格が必要高比表面積化のためには、グラフェンの両面を露出させる3次元骨格が必要

空想上のグラフェン3次元構造体

・グラフェンサイズが小さくなるとエッジ面の寄与が増大し、比表面積が増加する

・エッジの量が増えるため、（良くも悪くも）化学的活性が高くなる

・グラフェンサイズが小さくなるとエッジ面の寄与が増大し、比表面積が増加する

・エッジの量が増えるため、（良くも悪くも）化学的活性が高くなる

高表面積化の方法②エッジ面の利用

Novel Carbon Adsorbents,J.M.D. Tascon, ed.Elsevier, 2012.

3

FAU zeolite(template)

Zeoliteremoval

Carbonfilling

Nanographene

Carbon, 47 (2009) 1220.

Nanopore: 1.2 nm

3D nanographene-network

Zeolite-templated carbon (ZTC)

ZTC

Surface area is 3000~4000 m2/g!Surface area is 3000~4000 m2/g!

0.74～1.2 nm

Novel Carbon Adsorbents,J.M.D. Tascon, ed.Elsevier, 2012.

T. Kyotani, et al., Chem. Commun. (2000) 2365.

O: 17.1 wt%

Graphenegrowth

Templateremoval

3D graphene network

Supercage: 1.3 nmWindow: 0.74 nm

OH

+ H+, +e–

– H+, – e–

O

O: 8.4 wt%

Zeolite-templated carbon (ZTC)T. Kyotani, et al., Chem. Commun. (2000) 2365.

酸化グラフェンの仲間

Preparation method of ZTC①

stirrer

oil bath

N2 gas outlet

vacuumpump

N2 gas inlet

manometer

zeolite

furfurylalcohol

zeolite drying

furfuryl alcohol impregnation under vacuum

stirring for 8 h and filtration

washing with mesitylene

polymerization of FAat 150 ºC for 8 h

1st step:Furfuryl alcohol impregnation

OHO

quartz filter

thermocouple

temp. controller

quartz reactor

furnacegas cylinder

mass flow meter

N2 C3H6

sample

heat treatment of the composite up to 700 °C

propylene CVD at 700 °C for 1 h

further heat treatment at 900 °C for 3 h

2nd step:Propylene CVD

carbon liberation from the zeolite by HF washing

Preparation method of ZTC②

4

SEM images

ZTC

The bulk shape of zeolite template is replicated by ZTC.The bulk shape of zeolite template is replicated by ZTC.

Zeolite YCarbon/zeolite composite

10 nm

TEM images

Zeolite Y ZTC

The ordered structure of zeolite template is also replicated by ZTC.The ordered structure of zeolite template is also replicated by ZTC.

Due to space hindrance, single-layer nanographeneis formed inside the zeolite.

Carbon, 47 (2009) 1220.XRD patterns of zeolite Y and ZTC

2 (degree, Cu K)0 10 20 30 40 50

zeolite Y

(111)(111)

zeolite Y

ZTC

No (002) peak at 26°d-spacing = 1.4 nm

(111)

No (10) peak at 44°

5

250 200 150 100 50 0Chemical shift (ppm)

CP/MAS, delay: 10 s

SPE/MAS, delay: 10 s

SPE/MAS, delay: 100 s

ZTC is mainly comprised of sp2 carbon atoms.ZTC is mainly comprised of sp2 carbon atoms.

13C solid-state NMR spectra of ZTC

0 500 1000 1500 2000

Ramanshift (cm-1)

Raman spectra and XRD patterns

Raman spectra of ZTC and zeolite Y

Sharp G-band Graphene sheets

A broad peak in the low frequency region

ZTC

zeolite YSingle graphene without stacking

XRDno (002)

Curved nanographeneCarbon, 47 (2009) 1220.

Porous properties of ZTC

Very large surface area (4000 m2/g) and micropore volume (1.8 cc/g)Very large surface area (4000 m2/g) and micropore volume (1.8 cc/g)

SampleBET-SSA Vmicro Vmeso

(m2/g) (cm3/g) (cm3/g)ZTC 4080 1.8 0.2MSC-30 2770 1.1 0.4M-30 2410 1.0 0.8ACF-20 1930 0.7 0.5

ZTC

MSC-30

M-30

ACF-20

T. Kyotani, et al., Carbon, 43 (2005) 876.

N2 @ 77 K

MSC-30 : KOH-activated carbonM-30 : KOH-activated carbonACF-20 :activated carbon fiber

Pore size distribution of ZTC

ZTC has very uniform pores of 1.2 nm,compared to general activated carbons.ZTC has very uniform pores of 1.2 nm,compared to general activated carbons.

ZTC

Activated carbon

MSC-30 (Kansai Coke and Chemicals), KOH-activated carbonM-30 (Osaka Gas): KOH-activated carbonACF-20 (Osaka Gas):activated carbon fiber

T. Kyotani, et al., Carbon, 43 (2005) 876.

6

Electrochemical Capacitors (ECs)

10000

1000

100

100.01 0.1 1 10 100 1000

Aluminum condenserECs

Secondary battery

Energy density (Wh / kg)

Pow

er d

ensi

ty (W

/ kg

)

• Rare-metal free• Long cycle life

Backup power supply

Startup power supply for automobiles

Support for secondary battery

• High power density

Hybrid excavatorBus (Shanghai) Copy machine

Advantages of ECs

Electrochemical capacitance of ZTC

10 nm10 nm

Activated carbonCharge

Discharge

Battery

SeparatorCurrent collector Electrolyte

Random pore structure

Electrode

ZTC

10 nm10 nm

1.2 nmEt4N+

Ion-transfer resistance

Chem.－Eur. J., 15 (2009) 5355.

ZTC shows a good rate capability despite its small pore size (1.2 nm).ZTC shows a good rate capability despite its small pore size (1.2 nm).

Cap

acita

nce

/ F g

-1

-100

-200

0.40-0.4-0.8-1.2-1.6

0

100

200

1 mV/s, 25 ºC1M ‐ Et4NBF4 / PC

OCP

Potential / V vs. Ag/AgClO4

High rate-performance + high volumetric capacitance

Pore size : larger

0 5 10 15 200

20

40

60

Current density / A g–1

Volu

met

ricca

paci

tanc

e/F

cm–3

AC (0.71 g/cm3)

80

100

Micro/meso/macro porous carbon

ZTC (0.55 g/cm3)

Ion

Volumetric capacitance :Rate-performance :

ZTC

1.2 nmEt4N+ Ordered microporous structure

Carbon

Low ion-transfer resistanceReasonably high density

(0.36 g/cm3)

High rate-performanceHigh volumetric capacitance

Low density

J. Mater. Chem. 2008

1M Et4NBF4 / PC

JACS, 2011

J. Am. Chem. Soc., 133 (2011) 1165.Active materials for puseudocapacitors

polyaniline

polypyrrole

poly(3,4-ethylene-dioxythiophene)

Metal oxides

RuO2

NiOCo3O4

MnO2

V2O5

Conductive polymers

Large pseudocapacitance based on redox reactions

Limited rate capability and cyclability

Advantage

Disadvantages

7

Carbon materials for pseudocapacitorsComposites

Porous carbonsCarbon blacks

Carbon nanotubes

Pseudocapacitive materials

Grafting molecules

G. Pognen, et al., Carbon, 49 (2011) 1340Activated carbon

Functionalized carbonsOxidized carbons

N-doped carbons

B-doped carbons

C. H. Hsieh, et al., Carbon (2002)

D. W. Wang, et al., Chem. Mater. (2008)T. Kwon, et al., Langmuir (2009)X. C. Zhao, et al., Chem. Mater. (2010)

S. Shiraishi et al., Appl. Phys. A (2006)

C. O. Ania et al., Adv. Funct. Mater. (2007)

K. Jurewicz et al., Fuel Process. Technol. (2002)M. Kodama et al., Mater. Sci. Eng. B (2004)D. Hulicova et al., Chem. Mater. (2005)

E. Frackowiak et al., Electrochim. Acta (2006)G. Lota et al., Chem. Phys. Lett. (2005)

K. Jurewicz et al., Electrochim. Acta (2002)

E. Frackowiak et al., Carbon (2001)

K. Kinoshita, Carbon: electrochemical and physicochemical properties (1988)

G. Pognen, et al., J. Power Sources, 196 (2011) 4117

D. Bélanger, et al., Chem. Soc. Rev., 40 (2011) 3995

Electrochemical oxidation of ZTC

R. Berenguer, Carbon, 54 (2013) 94.

A large amount of oxygen-functional groups can be introduced in ZTC.A large amount of oxygen-functional groups can be introduced in ZTC.

Unique CV pattern of ZTC

ZTC is very easily oxidized compared to activated carbon.ZTC is very easily oxidized compared to activated carbon.

–0.2 0 0.2 0.4 0.6 0.8 1.0–1000

–500

0

500

10001500

2000

Potential (V vs Ag/Ag+)

Cur

rent

(mA

/g)

2500

–0.2 0 0.2 0.4 0.6 0.8 1.0–1000

–500

0

500

10001500

2000

Potential (V vs Ag/Ag+)

Cur

rent

(mA

/g)

2500ZTC

Activated carbon (MSC30)1st

2nd3rd4th

1st2nd3rd4th

A large anodic current !!Pseudocapacitance is small in the 1st cycle

(1M H2SO4)

After the oxidation, ZTC exhibits large pseudocapacitance.After the oxidation, ZTC exhibits large pseudocapacitance.

0

1.5

0.5

1.0

2.0

2.5

3.0

3.5

4.0

Temperature (ºC)

200 1000400 1400 16000 600 800 1200 1800

CO CO2 After CV + GCCO CO2 Pristine

0

1.5

0.5

1.0

2.0

2.5

3.0

3.5

4.0

0

1.5

0.5

1.0

2.0

2.5

3.0

3.5

4.0

Temperature (ºC)

200 1000400 1400 16000 600 800 1200 1800200 1000400 1400 16000 600 800 1200 1800

CO CO2 After CV + GCCO CO2 PristineCO CO2 After CV + GCCO CO2 After CV + GCCO CO2 PristineCO CO2 Pristine

Temperature (ºC)

200 1000400 1400 16000 600 800 1200 18000

1.5

0.5

1.0

2.0

2.5

3.0

3.5

4.0

CO CO2 After CV + GCCO CO2 Pristine

Temperature (ºC)

200 1000400 1400 16000 600 800 1200 1800200 1000400 1400 16000 600 800 1200 18000

1.5

0.5

1.0

2.0

2.5

3.0

3.5

4.0

0

1.5

0.5

1.0

2.0

2.5

3.0

3.5

4.0

CO CO2 After CV + GCCO CO2 PristineCO CO2 After CV + GCCO CO2 After CV + GCCO CO2 PristineCO CO2 Pristine

Change of TPD patterns (CO and CO2)

Des

orpt

ion

rate

(m

ol m

in–1

g–1 )

Des

orpt

ion

rate

(m

ol m

in–1

g–1 )

ZTC

In ZTC, CO-evolution groups are greatly increased !!

QuinonesPhenols

Ethers

Acid anhydrides

Activated carbon (MSC30)

8

Change of FT-IR spectrum

Phenols EthersQuinones

CxO + H+ + e– CxOH

Quinone/hydropuinone redox couple

Increasing scan potential range

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80–0.1–0.2 0.9–800

–400

0

400

800

1200 –0.1~0.4 V–0.1~0.5 V–0.1~0.6 V–0.1~0.7 V–0.1~0.8 V

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80–0.1–0.2 0.9–800

–400

0

400

800

1200

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80–0.1–0.2 0.9–800

–400

0

400

800

1200 –0.1~0.4 V–0.1~0.5 V–0.1~0.6 V–0.1~0.7 V–0.1~0.8 V

–0.1~0.4 V–0.1~0.4 V–0.1~0.5 V–0.1~0.5 V–0.1~0.6 V–0.1~0.6 V–0.1~0.7 V–0.1~0.7 V–0.1~0.8 V–0.1~0.8 V

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80–0.1–0.2 0.9–800

–400

0

400

800

1200 –0.1~0.4 V–0.1~0.5 V–0.1~0.6 V–0.1~0.7 V–0.1~0.8 V

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80–0.1–0.2 0.9–800

–400

0

400

800

1200

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80–0.1–0.2 0.9–800

–400

0

400

800

1200 –0.1~0.4 V–0.1~0.5 V–0.1~0.6 V–0.1~0.7 V–0.1~0.8 V

–0.1~0.4 V–0.1~0.4 V–0.1~0.5 V–0.1~0.5 V–0.1~0.6 V–0.1~0.6 V–0.1~0.7 V–0.1~0.7 V–0.1~0.8 V–0.1~0.8 V

ZTC

(1M H2SO4)(1st cycle)

Potential (V vs Ag/AgCl) Potential (V vs Ag/AgCl)

Cap

acita

nce

(F/g

)

Cap

acita

nce

(F/g

)

Activated carbon (MSC30)

CxO + H+ + e– CxOH

Quinone/hydropuinone redox couple

Structures before/after oxidationRaman XRD

Oxidation does not destroy graphene-based framework.Oxidation does not destroy graphene-based framework.

d-spacing = 1.4 nm

(111)

Pristine After oxidation

Edge sites are mainly oxidized.Edge sites are mainly oxidized.

OH

Graphenegrowth

Templateremoval

3D graphene network

Supercage: 1.3 nmWindow: 0.74 nm

+ H+, +e–

– H+, – e–

O

O: 8.4 wt%O: 17.1 wt%

9

Redox reaction in ZTC is very fast.Redox reaction in ZTC is very fast.

1M H2SO425 ºCRate performance0～0.8 V –0.1～0.8 V vs Ag/Ag+

Three-electrode cell Two-electrode cell

BCSJ, 87 (2014) 250.(BCSJ Award)

Cyclability

0 500 1000 1500 2000Cycle number

0

100

200

300

400

500

Cap

acita

nce

(F/g

)

1 A/g, 25 ºC, –0.1～0.8 V vs Ag/Ag+

Redox reaction is fully reversible.Redox reaction is fully reversible.

ZTC

MSC30

(1M H2SO4)

Asymmetric capacitor using ZTC

negative electrodeAC sheet

Au current collector

Vac. Impregnation+ 1 day impregnation

positive electrodeZTC sheet

Drying, IR-lamp, 1 h

Vac. Impregnation+ 1 day impregnation

Au current collector

Conducting adhesive(Colloidal graphite suspension)

AC ZTC

auxiliary ref.(Ag/AgCl in sat. KCl)

Oxidized in 1M H2SO4, 3 electrode cellexperimental set-up

mm

CC 2

1

max

Mass ratio

G.A. Snook, et al, J. Power Sources. 186, 216 (2009).

Carbon, 67 (2014) 792.Cyclability of the asymmetric capacitor

Capacitance of ZTC/AC is higher than…

• AC/AC(1.6 V) Benefit from the pseudocapacitive ZTC• ZTC/ZTC(1.4 V) The degradation of the negative electrode

Cell voltage of 1.4 V offers reasonable stability upon 5000 cycles of durability test.

Cell voltage of 1.4 V offers reasonable stability upon 5000 cycles of durability test.

more than 80 % retention

10

AcknowledgementsThis work was partially supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for young scientists (A), 23685041, by Grant-in-Aid for Scientific Research on the Innovative Areas: “Fusion Materials” (Area no. 2206), 23107507, and also by JST PRESTO.

Gunma Univ. Prof. S. Siraishi

Members of Kyotani’s group

Nissan Motor Co. Mr. M. Ito, Dr. M. Uchiyama

Aichi Inst. Technol. Dr. H. ItoiHokkaido Univ. Dr. S. Iwamura Kyoto Univ. Prof. M. Miyahara

Kyoto Univ. Dr. H. Tanaka

Tohoku Univ. Dr. K. NueangnorajTsinghua Univ. Prof. Q. H. Yang

Joint project membersUniversity of Malaga University of Alicante

Prof. José Rodríguez MirasolProf. Tomás Cordero AlcántaraDr. Raúl BerenguerDr. Juana María Rosas

Prof. Diego Cazorla-AmorósProf. Emilia MorallónDr. Ramiro Ruiz-RosasDr. Ángel Berenguer-MurciaDr. Dolores Lozano-Castelló