Recent Progress of Photocatalytic Water Splitting and Preliminary Work

1
Recent Progress of Photocatalytic Water Splitting
and Preliminary Work
Zhibin Lei Supervisor Prof. Can Li Jan. 13, 2003
State Key laboratory of Catalysis, Dalian
Institute of Chemical Physics
2
Content

• ? Significance of hydrogen energy
• ? Mechanism of photocatalytic water
• splitting
• ? Recent development of water splitting
• ? My preliminary work and next plan

3
Significance of hydrogen energy
The concentration change of CO2 in air during the
past one thousand years
4
The funds used for the hydrogen project of USA in
the past six years
5
????????????(??)
6
Predict hydrogen source in the next fifty years
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?????????????1.051018kWh,???1.3106?????
H2 ½ O2
H2O
Photocatalyst
Energy source Environment Economy
8
Mechanism of photocatalytic water splitting
TiO2 2 hv 2 e2 h (1)
(at the TiO2 electrode) 2 H 2 e
H2 (2) (at
the Pt electrode) H2O 2 h 1/2 O2
2 H (3) (at the TiO2 electrode) H2O 2
hv 1/2 O2 H2 (4)
(overall reaction)
A.Fijishima and K.Honda. Nature. 1972, 238, 37.
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hv
Pt
H H2
e-
CB
VB
h
RuO2
Schematic Water oxidation and reduction process
over photocatalyst
10
E vs NHE(pH0)
-1
e-
0 V
CB
H/H2
0
badgap
1.23 V
1
VB
O2/H2O
h
2
The relationship between the redox potential of
H2O and the VB-CB of the semiconductor
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hv
e-
CB
hv
VB
h
h
e-
H2O O2
H H2
h
e-
e-h
Schematic photoexicitation process in
semiconductor
12
Solar energy distribution detected at PM 12 in
Japan
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IR ?gt700nm
UV ?lt400nm
Vis 400-700nm
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Energy level diagram of transition metal oxide,
nitride and sulfide
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Recent development of water splitting
UV-Vis diffuse reflection spectra for Sm2Ti2O7
and Sm2Ti2S2O5
A. Ishikawa et al, J. Am. Chem. Soc., 2002, 124,
13547.
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Time course of O2 evolution from Sm2Ti2S2O5 and
CdS under visible light irridiation (Condition
catalyst 0.2g, La2O3, 0.2g, 0.01M AgNO3 solution
200ml)
A. Ishikawa et al, J. Am. Chem. Soc., 2002, 124,
13547.
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0.01M Na2SO3 0.01M Na2S
20ml CH3OH 180ml H2O
Time course of H2 evolution from 1.0 wt Pt-
Sm2Ti2S2O5 under visible light irradiation(? gt
440nm, catalyst, 0.2g solution volume, 200ml)
A. Ishikawa et al, J. Am. Chem. Soc., 2002, 124,
13547.
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Estimated band position of Sm2Ti2S2O5 at pH 0
and 8
A. Ishikawa et al, J. Am. Chem. Soc., 2002, 124,
13547.
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AgInS2
AgInZn7S9
ZnS
Diffuse reflection spectra of AgInZn7S9 (a), ZnS
(b) and AgInS2 (c).
A. Kudo et al, Chem. Comm., 2002, 1958.
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Photocatalytic H2 evolution over AgInZn7S9(a) and
3wt-Pt /AgInZn7S9 under visible light
irradiation(?gt420nm, catalyst, 0.3g 0.25 M
K2SO3- 0.35 M Na2S solution 300 ml.
A. Kudo et al, Chem. Comm., 2002, 1958.
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My preliminary work and next plan
The set up for photocatalytic water splitting
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Y 2.60E-4X0. 29 R 0.99676
Low yield part (Slt9120) hydrogen evolution
standard curve for System-1 and System-2(S-1, S-2)
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Y 1.92-4X2.31 R 0.99978
Middle yield part (9120ltSlt1400000) hydrogen
evolution standard curve for S-1 and S-2
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Y 3.18E-4X-159.6 R 0.99787
High yield part (Sgt1400000) hydrogen evolution
standard curve for S-1 and S-2
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Y 1.92E-3X-2.63 R 0.99951
Oxygen evolution standard curve for S-1 and S-2
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Y 2.56E-3X-3.50 R 0.99951
Nitrogen evolution standard curve for S-1 and S-2
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CH3OH 30ml, H2O 170ml
0.01M AgNO3 200ml, ?gt420nm
Time course of H2(A) and O2(B) evolution over
CdO-360 (condition catalyst, 0.5g 300W xenon
lamp)
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Photocatalytic O2 evolution over CdO calcinated
at varying temperature(Condition catalyst 0.5g,
0.01M AgNO3 200ml)
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Effect of La2O3 on the activity of the CdO
calcinated at 400C
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CdO-500-la2O3
CdO-400-la2O3
Photocatalytic O2 evolution over CdO calcinated
at 400 and 500?C(Condition catalyst 0.5g 0.01M
AgNO3 200ml la2O3, 0.2g)
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Photocatalytic O2 evolution over CdO-400 and 1
RuO2 loaded CdO-400(Condition catalyst 0.5g
0.01M AgNO3 200ml La2O3, 0.2g)
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R 11.2?mol/h
Photocatalytic O2 evolution over CdO calcinated
at 400C (Condition catalyst 0.5g, 0.01M AgNO3
200ml, La2O3 0.2g)
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Photocatalytic O2 evolution over CdO-500 and RuO2
loaded CdO-500(Condition catalyst 0.5g 0.01M
AgNO3 200ml La2O3, 0.2g)
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360 400 500
Uv-Vis diffuse reflection spectra for CdO
prepared at different temperature
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XRD pattern of CdO calcinated at 360?C
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1.0
CdIn2S4
CdS
0.8
Intensity(a.u.)
0.6
0.4
0.2
0.0
200
300
400
500
600
700
800
wavelengthen / nm
UV-Vis diffuse reflection spectra for CdS and
CdIn2S4 prepared by the solvothermal method.
37
XRD pattern of CdIn2S4 prepared by solvothermal
method
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Next Plans

1. To investigate the influence of other electron
   acceptor such as Fe3 and its concentration on
   the activity of CdO system.
2. To explore how the different loading species with
   varying amount will influence the O2 evolution.
3. To synthesize Cr or Ni doped CdO to enhance the
   position of VB of CdO.
4. To synthesize other sulfide with better activity.