Designed Nanostructured Materials for

Energy Conversion and Storage Devices

Jinwoo Lee, Ph. D.

Department of Chemical Engineering/School of Env. Sci. &EngPOSTECH

Outline

• Motivation

• Soft-Hard Integrated Assembly

• Fuel Cells

• Solar Cell

• Lithium ion battery

Soft-Hard Integrated method

Motivation

Alternative Energy Sources needed

Better Energy Conversion & Storage Devices

GISS Surface Temperature Analysis.http://data.giss.nasa.gov/gistemp/graphs/

Energy and Environmental Concerns

Synthesis of Mesoporous Silica Materialsusing Surfactant-Self-Assembly as Template

Soft-template method

Various Surfactant Self-Assemblies TEM of Mesoporous Silicaswith Uniform Pore Size

Kresge et al. Nature 1992, 359, 710.

Toward Ordered Mesoporous Crystalline Transition Metal Oxides

Non-siliceous mesoporous metal oxides (TiO2, Nb2O5….):Important for electrode materials and catalysis

Many Research Groups have pursued after discovery of MCM-41:Limited Success (Through Soft-Template Method)

Structure collapse occurs during the crystallization of the walls and removal of soft-template

Very recently, hard template was employed to make crystalline mesoporous metal oxides

Soft-template method

Stucky et al Nature 1998

Low-crystallinity

Not easy to preserve the porous strcutreafter heat-treatment

Maximum heating temperature: 400 oCfor 30 min Low-crystallinity

crystals

Hard template method

Mesoporous silicaMesoporous silica

/Metal oxideMetal Oxide

Fully crystalline

Tedious synthetic step

Bruce et al JACS 2006

600 oC

Soft Template

MCM-41 type synthesis

Hard template

Recently developed technique to make crystalline mesoporous metal oxides

Mesoporous silica Mesoporous silica/Metal oxide

Metal Oxide

Advantage: Simple Synthetic Method

Disadvantage: Low-crystallinity

Advantage: Fully Crystalline Materials

Stucky et al Nature 1998, 396, 152

Disadvantage: Very tedious Multi-Step Method

ZrO2

P. G. Bruce et al. J. Am. Chem. Soc. 2006, 128, 5468

We need a new efficient way

Li cyclohexane Li+ n

n

PI-b-PEO synthesis

L i +O

O HL i

nO H O+n

n-butyl lithium isoprene

ethylene oxide

nOH +

Kn

O +K

HTHF

Poly(isoprene)

Poly(isoprene)-b-poly(ethyleneoxide)

Kn

O +O n

Hm

Om

OH

Wiesner Research Group: Route to Mesoporous MaterialsPolymers as structure-directing agents for inorganics

TEM

F

100 nm

D

100 nm

E

Science (1997), JACS (1999, 2003), Angew. Chem. (2001, 2005), Chem. Mater. (2001)

Increasing the amount of inorganic material

CH3

OOHR

X Y

PI-b-PEOGoes intoPEO only+ + Al(OsBu)3

Si

MeOOMe

OMe

O

O

Hybrid Silica

Hexagonally arranged polymer-metal oxide hybrid

Highly crystalline mesoporous metal oxide with carbon

Fully crystalline meso-porous metal oxide

Soft and Hard Integrated Assembly (SHIA) Method

CH3

OOHR

X Y

PI-PEO

J. Lee et al 2007 Nature Materials revised version

Metal Oxide Nanoparticles

M(OR)x+MClx

700 oC 450 oC

20~30 nm

Mn~27,220, PEO~ 16.7wt%

1h 30 min

Argon

700 oC

Air

450 oC

J. Lee et al 2007 Nature Materials revised version

100 nm

2

10 20 30 40 50 60 70 80 90

Inte

nsity

0

200

400

600

800

d101

10 nm

2

10 20 30 40 50 60 70 80 90

Inte

nsity

0

200

400

600

800

Example: Mesoporous Anatase TiO2

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Iq2 (

a.u.

)

q (nm-1)

A q*=0.20

B q*=0.23

C q*=0.26

3 4

3 4

3 4

0.0 0.2 0.4 0.6 0.8

3

3

4

4

943

C q*=0.24

A q*=0.21

Iq2 (

a.u.

)

q (nm-1)

B q*=0.23

0 10 20 30 40 50 60 70

B

AInte

nsi

ty (

a.u

.)

2

SAXS-TiO2SAXS-Nb2O5

As-syn

TiO2-C

TiO2-SHIA

As-syn

Nb2O5-C

Nb2O5-SHIA

10 20 30 40 50 60 70 80

Inte

nsi

ty (

a.u

.)

2

TiO2-XRD Nb2O5-XRD

TiO2-C

TiO2-SHIA

Nb2O5-C

Nb2O5-SHIA

J. Lee et al 2007 Nature Materials revised version

TEM images of Fully Crystalline Mesoporous Transition Metal Oxides

100 nm

TiO2-as syn

100 nm

TiO2-SHIA

10 nm

d101

TiO2-SHIA

Nb2O5 as-syn Nb2O5-SHIA Nb2O5-SHIA

1000 1200 1400 1600 1800 2000

10000

20000

30000

40000

50000C

ou

nts

Wave number (cm-1)

D-Band

G-Band

TiO2-C

TiO2-SHIA

0 200 400 600 80090

92

94

96

98

100

Wt

%

Temperature ( 0C)

Raman Spectroscopy

Thermogravimetric Analysis

TiO2-C

TiO2-SHIA

0 10 20 30 40 50 60 70 80 900

200

400

600

800

1000

Inte

nsi

ty (

a.u

.)

2

Nb2O5-Air-400

Nb2O5-SHIA

X-ray Diffraction

The Mesoporous Nb2O5 via conventional way has nearly amorphous walls

+0.5

+100+100

+0.5

0.0 0.2 0.4 0.6 0.8 1.0

Vol

ume

Ado

srbe

d (c

m3 /

g)

0

50

100

150

200

250

300

Pore Diameter (nm)0 20 40 60 80 100

dV/d

log

D (

cm3 /

g)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Relative Pressure (P/P0)0.0 0.2 0.4 0.6 0.8 1.0

Vol

ume

Ads

orbe

d (c

m3 /

g)

0

50

100

150

200

250

300

Pore Diameter (nm)

0 20 40 60 80 100 120 140 160

dV/d

log

D (

cm3 /

g)

0.0

0.2

0.4

0.6

0.8

1.0

Relative Pressure (P/P0)

Nitrogen Sorption Experiment

TiO2-C

TiO2-SHIA

TiO2-C

TiO2-SHIA

Nb2O5-C

Nb2O5-SHIA

Nb2O5-C

Nb2O5-SHIA

BET surface area of TiO2 SHIA: 89 m2/g BET surface area of Nb2O5 SHIA: 54 m2/g

The normally heat-treated sample under air at 700 oC: BET surface area ~0.2 m2/g

Relative Pressure (P/P0)

0.0 0.2 0.4 0.6 0.8 1.0

Vol

ume

ados

rbed

(cm

3 /g)

0

10

20

30

40

50

60

70

80

AdsorptionDesorption

Pore Diameter (nm)

0 20 40 60 80 100 120

Por

e V

olum

e (c

m3/

g)

0.00

0.05

0.10

0.15

0.20

0.25

2 theta

10 20 30 40 50 60 70 80 90

Inte

nsity

0

200

400

600

800

1000

1200

1400

R

R

R

R

R

R

RR

RR

A

A

The mesopores was preserved even after heat-treatment at 1000 oC!!!

Anatase-Rutile mixture

200 nm

Fuel Cells

Fuel Cell Basics

Direct energy conversion device of fuel to electricity

H2

H+

e-

Load

e-

O2

H2O

cathodeanodemembrane

Here: electrode materials only

Anode: H2

Cathode: O2+2e-+2H+

2H++2e-

H2O

Issues with Current Electrode Materials

Carbon: Corrosion

Complicated synthetic method

PtRu Alloy: Poisoning & low mass activity

Intermetallic Nanoparticles on Mesoporous Metal Oxides

Solution

Claim to fame: Intermetallic catalyst

Pt-Pt distance:2.77 Å

The long Pt-Pt distance in intermetallic compounds precludes the adsorption of CO

Random geometry

Pt-Pt distance:4.32 Å

Only One Geometry

Integrating intermetallic catalyst in mesoporous TiO2

+

700 oC,Ar/H2

PtPb

PtPb

PtPb

PtPb

PtPb

PtPb

PtPb

PtPb

Wavenumber (cm-1)

1000 1200 1400 1600 1800 2000

Inte

nsity

8000

10000

12000

14000

16000

18000

Presence of carbon

GD

CH3

OOHR

X Y

PI-b-PEO TiO2Nanoparticles

Ti(OR)4+TiCl4

THF

Evaporation

PI +Pt

PEO+TiO2+Pb(MOEEAA)2

Pb(MOEEAA)2

J. Lee et al 2007, to be submitted

Pt

(2-[2-{2-methoxy}ethoxy]ethoxy)aceticacid (MOEEAA)

+

Metal Precursor

q (nm-1)

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Inte

nsity

1e+2

1e+3

1e+4

1e+5

Small-Angle X-ray scattering of As-syn material

Short-range ordered hexagonal

200 nm

Pore Diameter (nm)

0 50 100 150 200 250 300

Por

e V

olum

e (c

m3 /

g)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

q (nm-1)

0.000.020.040.060.080.100.120.140.160.18

Inte

nsity

0.001

0.01

0.1

1

10

100

1000

Nanoparticles dispersed in Uniform Large Mesoporous TiO2

17.6 nm, 144.3 m2/g

2

20 30 40 50 60 70

Inte

nsity

0

100

200

300

400

500

600

Carbon/silica matrix

Only PtPbIntermetallic

SAXS

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

-0.3 -0.2 -0.1 0 0.1 0.2 0.3

E (V vs. Ag/AgCl)

MA

(m

A/

g-P

t)FA (formic acid) oxidation

PtPb on TiO2/C-Intermetallic

Pt-Ru on Vulcan (E-TEK)-Alloy

(On-set potential:-0.18V)

(On-set potential:+0.10V)

Electrochemical testing of novel materials

A high mass activityMuch lower onset potential

CO stripping oxidation

-10

-8

-6

-4

-2

0

2

4

6

8

10

-0.3 -0.1 0.1 0.3 0.5 0.7

i (A

)

E (V) vs. Ag/AgCl (NaCl sat.)

: After CO bubbling: Before CO bubbling

-0.08

0

0.08

0.16

-0.3 -0.1 0.1 0.3 0.5 0.7

E (V) vs. Ag/AgCl (NaCl sat.)

i/A

PtPb in TiO2-Intermetallic

PtRu/Vulcan-Alloy

Much less CO poisoning

160

80

-80

Photovoltaics

Dye-sensitized solar cells

External circuit

Top electrodeI- / I3 basedelectrolyteFTO coated

glass

NanocrystallineTiO2 film

I3-

I-

Sensitizer dye

Current performance: =11%O’Regan, B. & Grätzel, M. - Nature 353, 737-740 (1991)

Solid state dye-sensitized solar cell

Top electrode

Solid hole transporter (Spiro)

FTO coated glass

NanocrystallineTiO2 film

Sensitizer dye

NN

NN

O O

OO

O

O

CH3CH3

O

O

CH3CH3

CH3 CH3

CH3 CH3

Spiro-MeOTAD2,2,7,7-tetrakis-(N,N-di-p-methnanoparoxyphenylamine)-9,9-spirobifluorene

Current performance: =4%Bach, U. et al. – Nature 395, 583-585, (1998)

h+

Collaboration with Cavendish Laboratory, University of Cambridge, UK

OE Group-Cambridge

Financial SupportPolyFilm EU-RTN

Prof. Ulrich Steiner

Nanoscience Centre

Prof. Sir Richard Friend

Cornell University USAProf. Ulrich Wiesner

Problem with Previous TiO2

Heat-treatment at low temperature: amorphous region still present

Nano Lett 2005, 5, 1791

350 oC~450 oC for 30 minutes

Soft-template

100 nm d101

10 nm

Argon

700 oC

Air

450 oC

J. Lee et al 2007 Nature Materials revised

2

10 20 30 40 50 60 70 80 90

Inte

nsity

0

200

400

600

800

2

10 20 30 40 50 60 70 80 90

Inte

nsity

0

200

400

600

800

Recap Mesoporous TiO2

Cross-section of mesoporous TiO2

X-ray of mesoporous TiO2

Angle (o)

Inte

nsity

(u.

a.)

Thickness of 1.1 m

Highly Crystalline Anatase

Dye sensitized solar-cell

Light absorption in dye, electron transfer to TiO2, hole transfer to Spiro-MeOTAD. NN

NN

O O

OO

O

O

CH3CH3

O

O

CH3CH3

CH3 CH3

CH3 CH3

C

CS

S

OH

O

NaO O

Ru

N

N

N

N

N

N

Dye Z907 Spiro-MeOTAD

1 m

Device results Performance parametersJ-V data as a function of temperature annealing

600oC 550oC 500oC 450oC

1.09

0.70

0.35

0.46

Jsc

(mAcm2)

2.0 2.54 0.71

Voc (V) 0.81 0.76 0.65

(%) 0.56 1.17 0.25

FF 0.35 0.61 0.54

As the temperature increased, the amorphous regions were converted

to crystalline materials

Composition Variations

MW = 15.5 K

MW = 33.5 K

MW = 84.4 K

250nm

250nm

250nm

Results

0

5

10

15

20

25

400 450 500 550 600 650 700 750

6.6 %16.5 %25 %33%

Ext

erna

l Qua

ntum

Effi

cien

cy (

%)

Wavelength (nm)

Another approach: Patent application being written

VERY EXCITING !!

Liquid electrolyte- 3.5 m

Facile synthesis of well-organized crystalline TiO2/carbon composites

for use as anode in Lithium ion batteries

Heat-treatment at 700 oC

AmorphousTiO2+PEO

Poly(furfuryl alcohol) or Resol

Conductive CarbonCrystalline TiO2(anatase)

One-pot assembly of PI-PEO, Ti(iOPr)4,TiCl4 and furfuryl alcohol /or Resol

Aging(polymerization)

Mesopores (~20 nm)PI part

200 nm

(a)

Temperature (oC)

0 200 400 600 800 1000

Inte

nsity

80

85

90

95

100

105

0.00 0.03 0.06 0.090.01

0.1

Iq2

q (A-1)

q=33.8 nm

q=26.6 nm

16wt% decrease

100 nm

As-syn

Mn=27,220 g/mol

As-syn

Meso-TiO2-carbon

Meso-TiO2-carbon

Wormhole structure:very good for diffusion of electrolyte and ion

Relative Pressure (P/P0)

0.0 0.2 0.4 0.6 0.8 1.0

Vol

ume

Ads

orbe

d (c

m3/

g)

0

50

100

150

200

250

AdsorptionDesorption

Pore Diameter (nm)

1 10 100

dV/d

log

D

0.0

0.2

0.4

0.6

0.8

1.0

2

20 40 60 80

Inte

nsity

0

5

10

15

20

25

30

Anatase (7.4 nm crystal)

Wave number (cm-1)

800 1000 1200 1400 1600 1800 2000 2200

Inte

nsity

4000

6000

8000

10000

12000

14000

16000

18000

20000

22000

G

D

154 m2/g, 0.3 cm3/g

9.4x10-3 S/cm

Meso-TiO2-carbon

Wall is composed of TiO2 nanoparticles

Shows crystalline wall

20 nm

TEM image

d101

Electrode was made without adding conducting carbon

0.65 Li/Ti for C-T700 and 0.60 Li/Ti for T450

0.55 Li/Ti for C-T700 and 0.30 Li/Ti for T450

Insertion capacity

Desertion capacity

Added small amount of conducting agent(to obtain best result)

One of best electrode materials:Excellent Cyclability and High Rate Capability

0.75 Li/Ti for insertion and 0.60 Li/Ti for de-insertion

From MPI, Chem.Commun, 2006, 2783

Nano-structured graphitic carbon/titanium dioxide composite by microphase

separation of PEO-PAN and titanium dioxide sol toward functional electrode material

PEO: Anionic polymerization PAN: ATRP

PEO-b-PAN TiO2 nanoparticles (generated from nonhydrolytic sol-gel)

Microphase separatedstructure

PAN

Amorphous TiO2+PEO

Carbon

Crystalline TiO2+PEO

Schematic representation

Self-assemblyat 70 oC or 90 oC

2. 700 oCUnder Ar

PEO-PAN:TiO2=1:2 (w:w)

1. Crosslinking

Background

Transition metal oxide/carbon composite materials have been synthesized to use as electrode materials

Typical method to make carbon/transition metal oxide compositeLoading of transition metal oxide in carbon materials

To make homogeneously mixed nanocomposite of carbon and metal oxide, ordered mesoporous carbon was used

Tin and phosphate source incorporation

Crystallize

Ordered mesoporous carbon with amoprphous framework

Zhao et al, Adv. Mater. 2004, 16, 1432

conducting Li ion insertion

TEM of microphase separated As-syn composite

The dark part is titanium oxide part

TEM image of carbon/crystalline TiO2 samples

Around 10 nm sized TiO2 anatase nanocrystals

2 theta

20 30 40 50 60 70 80

Inte

nsity

0

100

200

300

400

500

Anatase12 nm sized crystal

Carbon content ~10 wt% from TGA under air

F11C

Specific Capacity (mA h gTiO2

-1)

0 50 100 150 200 250

Vol

tage

(

1.0

1.5

2.0

2.5

3.0

Carbon/Titania composite, but, mesopores are needed to improve performance

After removal of carbon

Pore Diameter (nm)

0 20 40 60 80 100

dV/d

log

D

0.0

0.1

0.2

0.3

0.4

0.5

After removal of carbonCarbon/Titania composite

7.4 nm sized pores are generated by removal of carbon

Pore size distribution

Evidence of microphase seperation

PEO-b-PAN:a structure-directing agent for fully crystallinemesoporous transition metal oxides

BET surface area (m2/g)

Carbon/TiO2 52

TiO2 115

0.00 0.02 0.04 0.06 0.08 0.10

0.1

1

Iq2

q (A-1)

JL6 PEObPAN TiO2 250C-700C-carbon

JL7 PEObPAN TiO2 250C-700C-450C-TiO

2 only

Carbon/TiO2

TiO2-only

SAXS

Broad Pattern

)exp(BB

om Tk

KV

Magnetite/PSPI Nanofibers exhibit superparamagnetic properties.

• SQUID (Superconducting quantum interference device) data

10 wt% Magnetite NP (4nm)/IS53-143,annealed at 180oC for 48 hrs

Blocking temperature=13 K

Hierarchical carbon nanofiber

1 m1 m1 m

Hollow graphite is known to be good electrode material

100 nm

Wave number (cm-1)

800 1000 1200 1400 1600 1800 2000 22000

1000

2000

3000

4000

5000

6000

7000

8000

PAN-C

Fe-PAN-C

D

G

Raman Spectroscopy

More Graphitic

Magnetically Separable Electrode Materials

Magnet

MHCN/GOx

Au electrodeSwitch OFF

Switch ON

Magnet

Glucose Gluconolactone

e-

Summary

Intermetallic nanoparticles on mesoporous metal oxide were highly active fuel cell catalysts

Highly crystalline mesoporous TiO2 materials were successfully used as anode materials for high efficiency solid-state photovoltaics

High efficiency solar cell electrode was fabircated using soft-hard integrated self-assembly