Photocatalyst Materials Discovery and Systems Development · Solar Water Splitting: Photocatalyst...
Transcript of Photocatalyst Materials Discovery and Systems Development · Solar Water Splitting: Photocatalyst...
Solar Water Splitting: Photocatalyst Materials Discovery and Systems
Development
Thomas F. McNultyGE Global Research
May 23, 2005
Project ID # PDP34This presentation does not contain any proprietary or confidential information
Overview
2GEThomas F McNultyMay 23, 2005ID # PDP34
• Anticipated July 1, 2005 start• December 31, 2007 completion
Usable semiconductor bandgap:Materials Development
• Materials Efficiency• Materials Durability• Bulk Materials Synthesis
Systems Development• Systems Design and Evaluation
• $3.75MM total – $3.0MM DoE– $750k GE/Caltech
• $1.25MM FY05
Budget
Barriers
CaltechPartners
Timeline
Objectives
Program Objectives:• Development of Photoelectrochemical system exhibiting:
– 9% Solar to hydrogen efficiency– > 10,000 hrs durability– < $5.00 gge hydrogen costs
Program Objectives:• Development of Photoelectrochemical system exhibiting:
– 9% Solar to hydrogen efficiency– > 10,000 hrs durability– < $5.00 gge hydrogen costs
3GEThomas F McNultyMay 23, 2005ID # PDP34
FY05 Objectives:• Increased materials efficiency through band-gap engineering
– Valence band modification through anionic doping of oxides– Optimization of composition through high-throughput screening (HTS)– Optimization of particle morphology for cell design/manufacture
• Development of robust membrane technology
FY05 Objectives:• Increased materials efficiency through band-gap engineering
– Valence band modification through anionic doping of oxides– Optimization of composition through high-throughput screening (HTS)– Optimization of particle morphology for cell design/manufacture
• Development of robust membrane technology
Background
173
1% 5% 10% 15%
$66.48
$5.54
$5.54 $5.54$5.54$6.65$13.30
$4.43
1091 / 1110185 / 188Singapore
1305 / 1620221 / 275Honolulu
Production rate* kg/day
Average insolation in Jan / Jul (W/m2/hr)
Location
1369 / 1898229 / 317Phoenix
1148 / 1748195 / 296L.A.
634 / 1500112.5 / 254Albany
247.5 / 113242 / 192Ankorage
1091 / 1110185 / 188Singapore
1305 / 1620221 / 275Honolulu
Production rate* kg/day
Average insolation in Jan / Jul (W/m2/hr)
Location
1369 / 1898229 / 317Phoenix
1148 / 1748195 / 296L.A.
634 / 1500112.5 / 254Albany
247.5 / 113242 / 192Ankorage
*assumes 10% efficiency
PanelsBOS
1734.5 11.515 acres22 acres46 acres
229 acres
• System cost / efficiency critical technology drivers• Performance regional
• System cost / efficiency critical technology drivers• Performance regional
Example: 1000 kg/day remote refueling station in Albany, NY
4GEThomas F McNultyMay 23, 2005ID # PDP34
Concept
Photoelectrochemical element
O2 H2
Photoelectrochemical element
O2 H2
Advantages:• reduced cost• greater materials flexibility• H2 formed separately from O2
Advantages:• reduced cost• greater materials flexibility• H2 formed separately from O2
5GEThomas F McNultyMay 23, 2005ID # PDP34
Approach
H+/H2
H2O/O2
TiO
2, E g=
3.2
eV
KT a
O3,
E g= 3
. 5 e
V
S rT i
O3,
Eg=
3.7
eV
4.0
5.0
6.0
7.0
8.0
Ener
gy (r
el. v
ac. L
evel
)
Bi 2O
3, E g=
2.9
eV
P bO
, Eg=
2.8
eV
WO
3, E g=
2.7
eV
Valence band energy level attributed to O2p Mxdtransition
Position of valence/conduction bands vs. H2O redox
• Solar efficiency of oxides limited by VB position• Anionic substitution offers potential of reducing VB energy level
• Solar efficiency of oxides limited by VB position• Anionic substitution offers potential of reducing VB energy level
6GEThomas F McNultyMay 23, 2005ID # PDP34
Approach
• Anionic doping of TiO2 shown to reduce overall band-gap
• Conduction band effects not reported
• TiO2-xNx and TiO2-xCx not optimized
• Other systems (e.g. SrTiO3, KTaO3 not reported
• Long-term stability unknown
• Anionic doping of TiO2 shown to reduce overall band-gap
• Conduction band effects not reported
• TiO2-xNx and TiO2-xCx not optimized
• Other systems (e.g. SrTiO3, KTaO3 not reported
• Long-term stability unknown
Asahi et.al., Science, 293 (2001) 269-271
Kung et.al., Science, 297 (2002) 2243-2245
7GEThomas F McNultyMay 23, 2005ID # PDP34
Approach
• HTS demonstrated as useful technique to measure effects of compositional perturbation
• HTS coupled with reactive sputtering deposition to optimize concentration of nitrogen/carbon substitution
• HTS demonstrated as useful technique to measure effects of compositional perturbation
• HTS coupled with reactive sputtering deposition to optimize concentration of nitrogen/carbon substitution
8GEThomas F McNultyMay 23, 2005ID # PDP34
Technical ProgressCompositional optimization by HTS:
X
Y
• X-Y stage allows 48 samples to be sputtered sequentially
• Each sample can be sputtered at different N/Ar flow ratio varying from 0 to 20 vol%.
• Electronic circuitry fabricated directly on top of each sample
• Direct photoelectrochemicalmeasurement.
• X-Y stage allows 48 samples to be sputtered sequentially
• Each sample can be sputtered at different N/Ar flow ratio varying from 0 to 20 vol%.
• Electronic circuitry fabricated directly on top of each sample
• Direct photoelectrochemicalmeasurement.
Sputter ControlInterface
9GEThomas F McNultyMay 23, 2005ID # PDP34
Technical Progress
10GEThomas F McNultyMay 23, 2005ID # PDP34
Absorption vs. Wavelength
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
200 300 400 500 600 700 800
wavelength (nm)
abso
rptio
n (a
rb. u
nits
)
SrTiO3-xNx As-synthesized SrTiO3
SrTiO3-xNx As-synthesized SrTiO3
• Nitrogen substitution leads to absorbance state at lower energy
• Nitrogen substitution leads to absorbance state at lower energy
Valence band modification:
C as aXPS (This s tr ing can be edit ed in Cas aXP S.DEF/Pr in tF oot Not e. txt )
N1 1
N1
x 101
225
230
235
240
402 400 398 396 394 392 390Binding Energy (eV)
Technical Progress
11GEThomas F McNultyMay 23, 2005ID # PDP34
Photoanode O2
Quartz window
NorylGasket
Ag/AgCl Reference
Pt Cathode H2
hv
Photoelectrochemical cell:
• Modular• Split-cell, membrane cell, particulate capability• Upgradeable
• Modular• Split-cell, membrane cell, particulate capability• Upgradeable
Future Work
12GEThomas F McNultyMay 23, 2005ID # PDP34
• High throughput screening:– 48 sample thin-film array with individually-addressable cells for dopant optimization– nitrogen, carbon doping of oxides
• Powder optimization:– Optimization of powder morphology for incorporation into membranes– Bulk synthesis of powders identified in HTS– VB, CB measurements by UPS
• Membrane development:– Processing optimization– Characterization / optimization of surface morphology– Membrane-based photoelectrochemical testing