unimi.it - detoxification processes m hydrophilicity ......e-mail: [email protected]...
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ANATASE
RUTILE
Ti
O
ANATASE
RUTILE
Ti
O
Development of efficient and sensitive photocatalysts
for solar energy conversion and environmental
applications
Group of Prof. ELENA SELLI
M. Altomare, G.L. Chiarello, A. Costa, M. Guarino, E. Selli, Chem. Eng. J., 2012, 191, 394.
M. Altomare, E. Selli, Catal. Today, 2013, 209, 127.
Livestock manure detoxification
h+
e-
DEg
TiO2
M
NH3
h+ h+
N2
NO2-
NO3-
h+
e-
h+
hn
(NH2)oxNH3 aq
Solar energy conversion
e-mail: [email protected]
Semiconductor photocatalysts
UV VISIBLE IR
300 400 500 600 700 800 900
Wavelenght / nm
UV VISIBLE IRUV VISIBLE IR
300 400 500 600 700 800 900
Wavelenght / nm
Solar light spectrum
UV < 400 nm (> 3 eV)
Vis 400-800 nm (1.5 – 3 eV)
IR > 800 nm (< 1.5 eV)
A-•
D
Conduction band
Valence band
-
+
Eg
A
D+•
En
erg
y
hn
Reduction
Oxidation
Metal Oxide
Advantages …
Drawbacks …
• High oxidation ability
• Biologically/chemically inert
• Photo-stable
• Cheap
• High energy band gap
• Fast electron-hole recombination
• Industrial applications:
powders or films ?
Decrease of electron-hole recombination
TiO2
main crystal phases
Synthesis methods
• Sol-gel technique: FLEXIBLE
• Flame-spray pyrolisis: VERSATILE
• Hydro(solvo)thermal way: SELECTIVE
• Microwave assisted process: FAST
Photocatalyst characterisation
• X.R.P.D.
• X.P.S.
• B.E.T.
• UV-vis D.R.S.
• E.P.R.
• H.R.T.E.M.
Sensitisation to visible light
0.0
0.2
0.4
0.6
0.8
1.0
250 300 350 400 450 500 550
l (nm)
Ab
so
rpti
on
D_25_500
D_25_600
D_25_700
DRS spectra
M.V. Dozzi, S. Livraghi, E. Giamello, E. Selli, Photochem. Photobiol. Sci., 2010, 10, 334.
M.V. Dozzi, B. Ohtani, E. Selli, Phys. Chem. Chem. Phys., 2011, 13, 18217.
M.V. Dozzi, E. Selli, J. Photochem. Photobiol. C: Rev., 2013, 14, 13.
Preparation of noble metal (Au, Pt, Pd) modified TiO2
M.V. Dozzi, L. Prati, P. Canton, E. Selli, Phys. Chem. Chem. Phys., 2009, 11, 7171.
M.V. Dozzi, G. L. Chiarello, E. Selli, J. Adv. Oxid. Technol., 2010, 13, 305
M.V. Dozzi, A. Saccomanni, E. Selli, J. Hazard. Mater., 2012, 211, 188.
Synthesis
Photo-reduction Deposition-Precipitation
DP with UREA Surfactant-stabilized systems
Preparation of mixed oxide
WO3-TiO
2 systems
Preparation of TiO2 films for H
2 production
Pt
TiO2 NT
Ti
e-CB
h+VB
H2O
O2
2H+
HH22
hhnn
TiO2 nanotube (NT) arrays: anodization method
2.7µm 3.2µm
0
2
4
6
8
10
12
0 2 4 6 8 10 12 14 16 18
H2
pro
duction [m
L]
Irradiation time [h]
NT1
NT2
NT3
NT4
NT5
I run II run III run
M. Altomare, M. Allieta, L.G. Bettini, M. Pozzi, E. Selli, Appl. Catal. B, 2013, 136, 81.
Anodization time Effects of …
Electrolytic solution
Applied potential
Annealing temperature
G.L. Chiarello, E.Selli, L. Forni, Appl. Catal. B, 2008, 84, 332.
G.L. Chiarello, M.H. Aguirre, E. Selli, J. Catal., 2010, 273, 182.
G.L. Chiarello, D. Ferri, E. Selli, J. Catal., 2011, 280, 168.
Down-hill reactions
(ΔG° < 0 )
TiO2 doping with metal or non-metal elements
Organic pollutants oxidation
OH 2 CO 2 O 2 COOHCH2223
OH 2 CO 2 O 2
5 CHOCH
2223
Up-hill reactions
(ΔG° > 0 )
Water splitting H
2 production from photo-steam reforming
H2
½ O2
CO2 photoreduction to CH
4 or CH
3OH
Detoxification processes
Poisoning metals reduction
Solar fuels production
Solar Energy into Chemical Energy
Super hydrophilicity
Photovoltaic devices
Applications of TiO2 based materials
Self-cleaning
F. Riboni, L.G. Bettini, D.W. Bahnemann, E. Selli, Catal. Today, 2013, 209, 28.