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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 TiO 2 M NH 3 h + h + N 2 NO 2 - NO 3 - h + e - h + hn (NH 2 ) ox NH 3 aq Solar energy conversion e-mail: [email protected] Semiconductor photocatalysts IR 300 400 500 600 700 800 900 Wavelenght / nm IR UV 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 - + E g A D +• Energy 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 TiO 2 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) Absorption 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 TiO 2 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 WO 3 -TiO 2 systems Preparation of TiO 2 films for H 2 production Pt TiO 2 NT Ti e - CB h + VB H 2 O O 2 2H + H 2 h n n TiO 2 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 H 2 production [mL] 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 ) TiO 2 doping with metal or non-metal elements Organic pollutants oxidation O H 2 CO 2 O 2 COOH CH 2 2 2 3 O H 2 CO 2 O 2 5 CHO CH 2 2 2 3 Up-hill reactions (ΔG° > 0 ) Water splitting H 2 production from photo-steam reforming H 2 ½ O 2 CO 2 photoreduction to CH 4 or CH 3 OH Detoxification processes Poisoning metals reduction Solar fuels production Solar Energy into Chemical Energy Super hydrophilicity Photovoltaic devices Applications of TiO 2 based materials Self-cleaning F. Riboni, L.G. Bettini, D.W. Bahnemann, E. Selli, Catal. Today, 2013, 209, 28.
