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: elena.selli@unimi.it

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.