designed nanostructured materials for energy conversion and … · 2008-12-16 · -shia. 0 200 400...
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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
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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
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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
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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
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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
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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%
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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
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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
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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
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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
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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
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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
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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
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-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
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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)
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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)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
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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-
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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