Transcript The Clean Energy Challenge Prashant V. Kamat Radiation Laboratory and Dept Of Chemistry and Biochemistry Dept.

The Clean Energy Challenge
Prashant V. Kamat
Radiation Laboratory and
Dept Of Chemistry and Biochemistry
Dept. of Chemical & Biomolecular Engineering
University of Notre Dame, Notre Dame, Indiana 46556-0579
Support: US DOE, US Army & Indiana 21st Century
After Oil
Beyond Fossil Fuels
Farming Solar
I The Energy Challenge
II Nanotechonolgy to the rescue (?)
Catalysis with Nanoparticles
Solar Cells and
Fuel Cells
Humanity’s Top Ten Problems
for next 50 years
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
ENERGY
WATER
FOOD
ENVIRONMENT
POVERTY
TERRORISM &
WAR
DISEASE
EDUCATION
DEMOCRACY
POPULATION
2004
2050
6.5
~ 10
Billion People
Billion People
….. R. Smalley, Rice Univ.
Energy
Chemical
Nuclear
Mechanical
Energy sources
The first derives from chemical or photophysical energy that
relies on oxidizing some reduced substance, usually a
hydrocarbon, or absorbing sunlight to generate either heat or
electricity. The energy involved is that of a chemical bond or
fractions of an electron volt (eV).
The second involves nuclear reactions that release energy
either by splitting heavy nuclei or by fusing light nuclei. The
energy involved in nuclear reactions is in the region of 106
electron volts (MeV) per nuclear reaction.
The third is thermomechanical in the form of wind, water, or
geological sources of steam or hot water. The energy involved
is in the milli-electron-volt (meV) region from, for example,
water falling several tens of meters.
Energy Flow Diagram for the US
Energy flow diagram for the United States for 1999, in quads (1 quad = 1015 British thermal units =
2.92x1011 kWh). The average energy consumption in the United States is 0.42x10–6 quads per person per
year, and the US population is about 5% of that on planet Earth. Energy consumption is large compared
with food consumption (1.22x104 kJ per day per person , which translates to only 0.42x10–8 quads per
person per year). Some corresponding numbers for world energy consumption for 1999, in quads, are:
petroleum 149.7; natural gas 87.3; coal 84.9; nuclear 25.2; hydro, geothermal, solar, wind and other
renewables 29.9; total world energy production is 377.1 quads.
Energy Information Administration Office of Energy Markets and End Use. Annual Energy Review 1999 <http://www.eia.doe.gov/aer> (US
Department of Energy, Washington DC, 2000); Dresselhaus, M. S. and Thomas, I. L., Alternative energy technologies. Nature, 2001, 414,
332-337
Uppsala Hydrocarbon Depletion Study
Group
OIL AND GAS LIQUIDS 2004 Scenario
http://ww.peakpoil.net
Source: New York Times, Feb 18, 2005
Increasing demand is driving oil prices higher
Light Crude Oil (CL, NYMEX)
Monthly Price Chart
http://politicalhumor.about.com
News Quotes from April 01, 2005**
9am
U.S. used an average of 8.9 million barrels of gasoline a day this year,
up 2.2 percent from the same period in 2004, Energy Department data
shows.
Goldman Sachs predicted a "super spike" in oil prices, to $105 a barrel
by 2007. The forecast helped push oil futures prices sharply higher.
"With OPEC capacity only a million barrels a day away from their limits
and demand rising, add a major outage somewhere and sure it's
possible," said Tom Bentz, an analyst at BNP Paribas Commodity
Futures.
Gasoline prices would have to reach $4 a gallon to stop American
consumers from driving gas-guzzling vehicles, Goldman Sachs
concludes.
5pm
Oil prices rallied to a record close above $57 a barrel Friday, sparked by
a surge in gasoline futures that could send the average retail cost of
gasoline above $2.25 a gallon within a few weeks.
** Note: These are not April Fool Jokes! These are real news clips of the day
THE END OF
CHEAP
Oil
After Oil
The U.S. tax code offers a $2,000
consumer credit for hybrid car owners and a
deduction of up to $100,000 for people who
buy the largest SUVs for business use!
…..It's inevitable. But just how soon will the vital fuel
become so scarce and expensive that we're forced to make
hard choices about how we live?
…Some experts, in fact, think the world production peak is
already here. The timing rests largely on the actions of
Middle East producers and on moves to conserve and to
develop unconventional sources.
Graph: World Oil Production 1950-2050
Source: Dr. C.J. Campbell
"Understanding depletion is simple. Think of an Irish pub. The glass
starts full and ends empty. There are only so many more drinks to
closing time. It’s the same with oil. We have to find the bar before we can
drink what is in it."
Campbell
The old way to address the problem …….
New York Times April 25, 2005
But will it work this time?
Saudis are already pumping oil at rates closer to their
maximum sustainable capacity than during previous price
spikes, leaving them less leeway to increase the supply on the
global market.
In 2002 Saudi Aramco, the state owned oil company, says it
produced 6.8 million barrels of oil per day. The Saudis now
produce about 9.5 million barrels a day.
The spare capacity available to the Saudis is estimated to be
down to about 1.2 million barrels a day.
Global warming over
the past millennium
Very rapidly we have entered
uncharted territory -– what some call
the anthropocene climate regime.
Over the 20th century, human
population quadrupled and energy
consumption increased sixteenfold.
Near the end of the last century, we
crossed a critical threshold, and
global warming from the fossil fuel
greenhouse became a major, and
increasingly dominant, factor in
climate change. Global mean surface
temperature is higher today than it’s
been for at least a millennium.
…… Marty Hoffert NYU
This shift is hard to explain without attributing it in part to humancaused global warming
….. National Snow and Ice Data Center in Boulder, CO.
(NY Times, Sept 29, 2005 )
Environmental Impact of Rise in Global Temperature
Oceans getting warmer.
A measure of regional storm activity.
Annual mean SST anomalies relative to 1961
to 1990 ( 23) for 1870 to 2004, averaged over
the tropical Atlantic (10°N to 20°N, excluding
the Caribbean west of 80°W) (top) and the
extratropical North Atlantic (30°N to 65°N)
(bottom). Heavy lines are 10-year running
means.
The ACE index reflects the collective intensity and
duration of tropical storms and hurricanes during a
given hurricane season. Values are given as
percentage of the median from 1951 to 2000; the white
band indicates normal conditions, the blue is below
normal, and the pink is above normal, according to
NOAA.
Kevin Trenberth. Science 38, 1753 (17 Jun 2005)
Forecasters could run out of names from the list of 21 for
tropical storms and hurricanes before the 2005 season
ends November 30. Only four names left for the year!
2005
Beyond 2010 new carbon-free primary
power technologies will increasingly be
needed (~10TW by 2050)
The United Nations Framework Convention on
Climate Change calls for ‘‘stabilization of
greenhouse-gas concentrations in the
atmosphere at a level that would prevent
dangerous anthropogenic interference with the
climate system . . .’’. A standard baseline
scenario that assumes no policy intervention to
limit greenhouse-gas emissions has 10 TW (10 x
1012 watts) of carbon-emission-free power being
produced by the year 2050, equivalent to the
power provided by all today’s energy sources
combined.
…………….NATURE, VOL 395, 881,1998
Decarbonization, CO2 sequestering ….
Improved energy efficiency in motor vehicles, buildings and
electrical appliances
Three possible options for meeting the 10 TW- Challenge by 2050
Carbon Neutral Energy (fossil fuel inconjunction with carbon
sequestration)
-Need to find secure storage for 25 billion metric tons of CO2 produced
annually (equal to the volume of 12500 km3 or volume of lake superior!)
Nuclear Power
-Requires construction of a new one-gigawatt-electric (1-GW) nuclear
fission plant everyday for the next 50 years
Renewable Energy Sources
- hydroelectric resource 0.5 TW
- from all tides & ocean currents 2 TW
- geothermal integrated over all the land area 12 TW
- globally extractable wind power 2-4 TW
- solar energy striking the earth 120,000 TW !!!
The Silver Lining …….
The earth receives more energy from the sun in just one hour
than the world uses in a whole year.
Cumulative solar energy production accounts for less than
0.01% of total Global Primary Energy demand.
Solar Energy demand has grown at about 25% per annum over the past
15 years (hydrocarbon energy demand typically grows between 0-2%
per annum). Worldwide photovoltaic installations increased by 927 MW
in 2004, up from 574 MW installed during the previous year.
An average crystalline silicon cell solar module has an
efficiency of 15%, an average thin film cell solar module has an
efficiency of 6%. (Thin film manufacturing costs potentially are lower,
though.)
Solar Energy (photovoltaic) prices have declined on average
4% per annum over the past 15 years.
For the Fiscal Year 2002, the Japanese solar roof top program received
applications from 42,838 households.
Without incentive programs, solar energy costs (in an average sunny
climate) range between 22-40 cents/kWh for very large PV systems.
(installation costs $8-$10 with no government incentives)
Japan has taken over from the United States as the largest net
exporter of PV cells and modules. Around 50 % of the world's
solar cell production was manufactured in Japan in 2003.
United States accounted for 12%.
www.solarbuzz.com
Solar Energy Cycle
Reflection 30%
173, 000 TW
Long
Wavelength
Radiation
Winds Waves
Convection
<1% (370 TW)
Conversion to
Heat 47%
Evaporation
Storage in
water/ice 23%
Tidal
Volcanic
3 TW
Storage in
plants <1%
(40TW)
EARTH
30TW
Fossil Fuels
Thermal, Nuclear
PV Land Area Requirements
Six boxes showing land area requirements to produce
20 TW of photovoltaic energy at 10% efficiency.
Boxes showing land area requirements to produce 3 TW
or 20 TW of photovoltaic energy at 10% efficiency.
Hoffert et al., Advanced
Technology Paths to Global
Climate Stability: Energy for a
Greenhouse Planet. 2002,
298, 981-987.
Mass-produced widely distributed PV arrays and wind turbines making electrolytic H2 or electricity may
eventually generate 10 to 30 TW emission-free. The global grid proposed by R. Buckminster Fuller with
modern computerized load management and high-temperature superconducting (HTS) cables could transmit
electricity from day to night locations
Energy Conversion Strategies
Fuel
Need for alternative energy
sources –Solar Energy
Light
Electricity
Fuels
Electricity
CO2
O2
H2
e
e
Sugar
M
SC
SC
H 2O
M
H 2O
O2
Photosynthesis
Semiconductor / Liquid
Junctions
Photovoltaics
Efficiency of Photovoltaic Devices
Efficiency (%)
25
20
15
10
crystallline SI
amorphous SI
nano TiO2
CIS/CIGS
CdTe
5
1950
1960
1970
Year
1980
1900
2000
Margolis, Science 285, 690, 1999)
Overcome the
environmental issues –
Greenhouse effect
Decrease the cost per watt
by improving the efficiency
–solar paint, flexible
cells
Photoelectrochemical Cell
Low surface area
Higher cost
Higher efficiency
e–
SrTiO3
KTaO3
TiO2
e–
–
O2
e
H2
metal
SnO2
H2O
Fe2O3
H2O
h+
Solid
Single Crystal Semiconductor
Liquid
Light is Converted to Electrical + Chemical Energy
Solar-Driven Photoelectrochemical Water Splitting
H2
g
O2
Glass or
plexiglass
Aqueous
electrolyte
H2
Porous
Photoelectrochemical cells
membrane
O2
High surface area
Low cost
Low efficiency
Stainless steel or
conducting plastic
Polycrystalline or nanostructured films
1. Semiconductor Assisted Catalysis
Single Crystal versus Nanoparticle
ECB
e
EF
EVB
h
–
CB
–
et
+
h
+
hn
VB
Red
t
Ox
Issues: Charge separation and charge transport
Semiconductor (e.g., TiO2) nanoparticles for hydrogen production
Hydrogen Evolution
rates for various
Photocatalysts (ml/hr)
H2
2H+
Pt
2H+
–
CB
–
et
ht
+
hn
+
VB
4OH2H2O+ O2
Issues:
Pt/TiO2
Pd/TiO2
Rh/TiO2
Ru/TiO2
Sn/TiO2
Ni/TiO2
TiO2
7.7
6.7
2.8
0.2
0.2
0.1
<0.1
Toshima, J. Phys. Chem. 1985, 89, 1902
What about gold and other noble metals?
- Explore size dependent properties of nanometals and alloys
How to extend the response into the visible?
- Design new photocatalysts and composites
How to improve the photocatalytic efficiency?
-Understand the charge transfer processes at the interface
Band Edge and Energetic Considerations
Bandgap
Band edge overlap
Fast charge transfer
All three energetic conditions
must be satisfied
SIMULTANEOUSLY + Stability
H2O / H2
V vs. NHE
-2.0
CdSe
+3.0
1.7
3.0
VB
+2.0
TiO2
1.4
2.4
+1.0
Counter
Electrode
H2O / H2
GaAsCdS
3.0
1.23 eV
p-type
semiconductor
SIC
CB
-1.0
0.0
Eg > 1.7 eV
MoS2Fe O
H+/H2
2 2
In2O3 WO
3
1.2
CdO
2.2
2.7
2.8
2.1 eV Eg
2. SOLAR CELLS
Efficiency Compared with Cost Per Unit Area of PV Devices (The diagonal lines show installed
2001 price of modules per peak-watt. The theoretical limit for Shockley-Queisser devices
[present limit] is 32
Third generation devices [shown in red] may exceed this limit by using multiple absorbers, hot
carrier effects, or photocurrent doubling via impact ionization. The latter two phenomena are
associated with quantum size effects in semiconductors and are being studied in semiconductor
nanocrystals).
L. Kazmerski, Solar-Electric Power: A 2001 Device Overview, National Center for Photovoltaics, National Renewable Energy
Laboratory, Golden, CO (2001).
M. Green, Annual Report, Third Generation Photovoltaics, University of New South Wales, Sydney, Australia (2000).
A grand Challenge for Solar Cells
Innovative technology is essential to bridge the gap
between existing photovoltaic devices and the
efficiency limits
100
Efficiency %
80
60
40
Thermodynamic limit
(Maximum concentration)
Thermodynamic limit
(One Sun)
How to bridge
these gaps
Existing tandems
(concentrator)
20
0
One-sun Si cell
efficiency
Now
Time
http://www.er.doe.gov/production/bes/reports/list.html
Can we address the clean energy
challenge with advances in
Nanotechnology?
Nanoworld
Nature Materials, February 2005
Commentary
To be nano or not to be nano?
CHRISTIAN JOACHIM
Nanomaterials, nanostructures, nanostructured materials,
nanoimprint, nanobiotechnology, nanophysics, nanochemistry,
radical nanotechnology, nanosciences, nanooptics, nanoelectronics,
nanorobotics, nanosoldiers, nanomedecine, nanoeconomy,
nanobusiness, nanolawyer, nanoethics to name a few of the nanos.
We need a clear definition of all these burgeoning fields for the sake
of the grant attribution, for the sake of research program definition,
and to avoid everyone being lost in so many nanos.
Galatée aux Sphères
(Salvador Dali, 1952).
Nanoscience is the study of phenomena and manipulation of materials at
atomic, molecular and macromolecular scales, where properties differ
significantly from those at a larger scale.
…….Royal Society of London report Nanoscience, and Nanotechnology: Opportunities and Uncertainties, 2004
Unique Aspects of nanostructures
• Organization of molecular-
Energy
Unoccupied
particle composites
• 2- and 3-D assemblies
• Control of electronic and
EF
Occupied
surface properties
Atom
Applications
• Optoelectronics, photonics, displays
• Chemical and biosensors
• Catalysis, photovoltaics and fuel cells
Bulk
Particles Semiconductor
Density of States
Quantized double layer charging
effects
Murray et al. Science, 1998, 280, 2098 and
Anal. Chem. 1999, 71, 3703
e
Quantized conductance through individual
rows of suspended gold atoms
H. Ohnishi, Y. Kondo & K. Takayanagi
Nature, 395, 780 (1998)
DV= [e/CCLU]
Au
where e is the electronic charge
and CCLU is capacitance (aF)
……...metal core potentials change by
>0.1V increments for single electron
transfers at the electrode
electrolyte interface
2 mA
DPV
5 mA
CV
0.8
0.4
0.0
-0.4
P o ten tial vs A g -Q R E
-0.8
unit conductance G0= 2e2/h.
Molecular Engineering of Inorganic-Organic Hybrid Assemblies
Achieving organized assembly
of inorganic-organic hybrids
may be the key of exploiting the
strength of nanomaterials
e
Molecular linker
GoldPt
TiO
TiO22
Inorganic-Organic Hybrid Assemblies for Solar Cells
hn
e
e
-OOCTiO2
Conducting
electrode
Au
Fluorophore
Electron
Donor
e
Can a hierarchial organization provide vectorial charge transport?
Ways to assemble elementary nanoobjects
Wire connected to Metal
or SC Nanoparticle
Particles
connected
by small
molecules
Metal capped
Particles
SC
particle
Au S
-S
SS
C
O
O-
S
S-
Au
-S
COO
TiO2
-
OOC
S
S-
-S
S Au
S
Scheme 2
Metal,
Catalyst
Strategies to match the sensitizer response with the solar spectrum
Characterization Standard:
• power density of 1000 W/m2
• spectral power distribution
corresponding to AM1.5 ≡ 1Sun
Nanostructured Hybrid Assemblies
hn
e
e
e
Ag
h
h
h
TiO2
Our Approach
•
reactant
products
Photocatalysis using semiconductor-metal
composites
S
S
S
S
S
S
S
A u
S
S
S
S
S
S
S
•
Quantum dot solar cells
•
SWCNT as the support architecture to improve
charge collection efficiency
S
S
e
CdSe
TiO2
hn
Electrode
Example 1
Charge Distribution in TiO2-Metal System
e e e e
EF
e e e
hn
EF
Au
h
TiO2
C2H5OH
Jakob, M.; Levanon, H.; Kamat, P.V., Charge
Distribution between UV-Irradiated TiO2 and Gold
Nanoparticles.
Determination of Shift in Fermi
Level,. Nano Lett. 2003, 3, 353-358.
Subramanian, V., Wolf, E. E. and Kamat, P. V.,
Catalysis with TiO2/Au Nanocomposites. Effect of
Metal Particle Size on the Fermi Level Equilibration.
J. Am. Chem. Soc., 2004, 126, 4943-4950.
Hirakawa and Kamat J. Am. Chem.
Soc., 2005, 127, 3928-3934
Sequential Electron Transfer
0.5
e
a
0.4
C60-
Absorbance
0.3
a
b
c
d
e
f
0.2
0.1
0.0
TiO2,UV120
Au8,0.2mM
[C60]-5.9mM
[C60]-11.7mM
[C60]-17.5mM
[C60]-23.2mM
c
e
e
Au
hn
e
C60
h
C2H5OH
TiO2
b
-0.1
-0.2
f
e
400
600
800
Wavelength,nm
1000
1200
TiO2
TiO2(e)
TiO2(e) + Au
TiO2/Au(e) + C60
….(a)
TiO2/Au(e) (b)
TiO2/Au+ C60-
..(c-f)
Reduction Efficiency (%)
Effect of Gold Particle Size on the Catalytic
Reduction Efficiency of TiO2 particles
(a)
15
10 nm
(b)
10
5
10 nm
0
1
2
3
4
(c)
a
Vaidyanathan, Wolf, Kamat J. Am. Chem. Soc., 2004, 126, 4943-4950
b
5 nm
Charging and Discharging
of Electrons in the Metal
Core
480
440
460
420
Ag @SiO2
440
400
Ag @TiO2
420
380
0
10
20
Time, min
30
40
2
After irradiation.
Peak position, nm
450
Off
Abs.
Irradiation On
Peak position of plasmon, nm
Peak position of plasmon, nm
(A)
3
440
430
420
0
1
1
2
3
4
Concentration of TH, mM
5
After addition of TH
0
300
400
500
600
700
800
Wavelength, nm
Hirakawa, T. and Kamat, P. V., Electron Storage and Surface Plasmon Modulation in Ag@TiO2 Clusters.
Langmuir, 2004, 20, 5645-5647
Example 2
Dye Sensitized Photochemical Solar Cells
Development of SC nanocluster
based cells with more than 10%
power conversion efficiency.
Photon-to-photocurrent efficiency
up to 100% has been claimed!
Source: http://dcwww.epfl.ch/icp/ICP-2/icp-2.html
Principle of Dye-sensitized Photochemical Solar Cell
Photovoltaic versus Dye sensitization
M. Grätzel, Nature 2001, 414, 338−344.
B. O’Regan, M. Grätzel, Nature 1991, 353, 737−740
Example 3.
Photochemical Solar Cells based on Molecular Assemblies
(Mimicking photosynthesis using porphyrins and chlorophyll)
2.0
0.75 mM (H 2P)n
in MeCN : toluene = 9 : 1
NH
N
H
H
N
HN
Absorbance
1.5
18mM H 2 P in MeCN
1.0
0.5
H2P
0
300
400
500
600
700
800
Wavelength, nm
Molecular clusters formed in mixed solvents exhibit broader absorption bands
Designing chromophore assemblies that can harvest visible light
(Mimicking photosynthesis with donor-acceptor assemblies
e
N
CH3
O
hn
e
N
CH3
Photoinduced electron transfer in a donor
acceptor dyad
Photoinduced electron transfer between
excited donor and acceptor molecules in a
cluster assembly near the electrode surface
Issues
How to harvest photons from a wide spectral range?
- Develop new photochemical systems that respond in IR
How to improve the efficiency beyond the limit of 10-12%?
- Design ordered assemblies of molecules and particles
- Improve photoinduced charge separation
Preparing Self Assembled Molecular Clusters
Hasobe, Fukuzumi, KamatJ. Mater. Chem., 2003, 13, 2515 – 2520;
and J. Phys. Chem. B, 2003, 107, 12105 – 12112
H2P
C60
+
NH N
N HN
toluene
H2 P-ref
Nanoclusters
Electrodeposition
(H2P+C60)n
H
CH2)n SH
Zn
n = 5, 11, 15)
n = 11, 15)
Formation of microcrystallites by Slow
evaporation of solvent
Charge Seperation and Charge Propagation in Cluster Films
hn
Red
Ox
(A)
8
0.4
20
40
60
Time, s
80
100
(B)
100 mV
Photoinduced charge
separation in H2P-C60
clusters results in
photocurrent
generation
IPCE, %
6
0
4
0.2
2
0.1
0
0
90
180
270
Time, s
360
450
540
0.3
400
600
500
Wavelength, nm
0
700
Absorbance
100 m/cm
2
Porphyrin-Gold-C60 as Light Harvesting Assembly
(A)
30
0.5 mA cm-2
d
S
S
S
S
IPCE, %
S
S
A u
S
20
0
S
S
S
S
40
S
S
A u
On
160
200
S
S
Off
S
S
Off
On
S
S
e-
10
a
NH N
N0 HN
NHCO
400
(n = 5, 11)
+
600
700
OTE/SnO2
0
220
Wavelength, nm
d
40
c
S S S
440
S S S
S
S
S
S
S S S
S
S
S
S
S
S S S
e-
S
S
S
S
S
S
S
S S S
S
S
S
S
S S S
S S S
S
S
S
S
S S S
e
S
-
I- / I3-
Pt
S
S
S
S
S
660
S
S
S
S
S
S S S
S
S
S
S
S S S
S
Time, s
[C60]
50
S
S
S
S
S
OTE
(B)
60
S
S
S
S
S
mV
(H2P-Au+C60)200
n
(CH2)n SH
500
hn
e-
c
SH
b
Porphyrin
(C)
400
C60
Gold Nanoparticle
OTE: Optically Transparent Electrode
H2Pc-Au-C60
0.3 mM
300
30
, mV
a
200
V
b
oc
IPCE, %
120
Time, s
S
S
(B)
S
80
S
S
S
S
S
S
S
S
S
S
20
0
100
b
10
a
0
0
400
H2Pc-C60
600
800
Wavelength, nm
1000
0
0.2
0.4 0.6 0.8
Isc, mA cm -2
1.0
1.2
Power Conversion
Efficiency ~2%
J. Am. Chem. Soc. 2003, 125, 14962-14963; J. Am. Chem. Soc, 2005, 127, 1216-1228.
Example 4
Quantum Dot Solar Cells
Tunable band edge
Offers the possibility to harvest light energy over
a wide range of visible-ir light with selectivity
Hot carrier injection from higher excited state
(minimizing energy loss during thermalization of
excited state)
Multiple exciton generation solar cells.
Impact ionization allows single high energy
photons to multiple electron-hole pairs
Robel, Bunker, Kamat J. Am. Chem. Soc. 2006,128, 2385-2393
Quantum Dot Solar Cells
e
CdSe
a
TiO2
hn
Electrode
HOOC
OOC
SH
SH
HOOC
OOC
SH
SH
HOOC
OOC
SH
OTE
Bifunctional
linker molecule
TiO2
SH
Chemically Modified
TiO2 film
OOC
OOC
SSH
OOC
SH
OOC
OOC
S-
OOC
SSH
CdSe
OTE/TiO2/CdSe
Electrode
b c
d
e
Photocurrent Generation
200
20
d
TiO2
TiO2/TAA/CdSe
TiO2/MDA/CdSe
TiO2/MPA/CdSe
c
10
b
a -TiO2
b -TiO2/CdSe
150
-ISC, mA
IPCE, %
15
a
b
c
d
b
100
50
5
0
400
a
0
a
500
600
Wavelength, nm
700
0
100
200
300
Time, min
Robel, Bunker, Kamat J. Am. Chem. Soc. 2006,128, 2385-2393
Example 5
Charge Injection from Excited CdS into SWCNT
0.0
C
-0.4
a
b
CdS + hn  CdS (e…h)
-0.8
-1.6
CdS(e) + SWCNT  CdS + SWCNT(e)
0.01 OD
a
-1.2
DA
DAx10
2
b
CdS
CdS-CNT
450nm
0
400
800
550nm
1200
1600
Delay time, ps
B
Photocurrent generation
e
0.2
0.0
DAbsorbance
IPCE, %
B
200nm
0.4
400
500
600
Wavelength, nm
400
500
Wavelength, nm
600
Summary

Opportunities exist for Nanotechnology to promote
revolutionary and important breakthroughs in energy
conversion technology.

Unique properties of quantum dots need to be exploited
for developing low-cost and high efficiency solar cells

SWCNT based hybrid assemblies are useful for
designing next generation solar cells and fuel cells.
Researchers/Collaborators
Ravi Subramanian (2004)
Roxana Nicolaescu (2004)
Istvan Robel (Physics)
Brian Seger (Chem. Eng.)
Ben Merritt (Chemistry)
Said Barazzouk, U. of Quebec, 2005 Anusorn Kongakanand
T. Hasobe, Osaka University, 2004
P. K. Sudeep
Kensuke Takechi
Yochiro Matsunaga
Dr. K. George Thomas (RRL, India)
Prof. Fukuzumi (Osaka U.)
Prof. T. Ebbesen
Prof. K. Vinodgopal (IUN)
For more information see …. http://www.nd.edu/~pkamat