UV and visible photoactivity of titania:nature of reduced and doped TiO2 from first principle calculations

24 June 2010 (Thu) 16:15 - 17:00

4F seminar room (#431-2), MANA Bldg. Namiki site / 並木地区MANA棟4Fセミナー室

Prof. Gianfranco Pacchioni

Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca

UV and visible photoactivity of titania:nature of reduced and doped TiO2 from first principle calculations

Titania is an essential component of new generation devices for photocatalysis and solar energy conversion. Its special behavior under illumination is at the basis of several practical applications like self-cleaning and self-sterilizing surfaces, superhydrophilicity, corrosion protection, etc. Most of these effects are observed under UV light and efforts are now oriented to the preparation of visible light photoactive titania. In this talk we will review the most recent advances in this field, and we will discuss in more detail the nature of doped TiO2 and of the interplay of intrinsic defects (like oxygen vacancies resulting in the formation of “Ti3+” ions) and states induced by transition and non-transition metal dopants like Cr, Sb, B, C, N, and F. The addition of heteroatoms, of crucial importance to improve the photactivity of the material, results in new states in the gap of titania and in paramagnetic centers. These centers may contribute to improve the photoactivity of the material under visible light but can also act as recombination centers for electrons and holes, thus resulting in a reduced activity. The description of these systems with advanced theoretical methods presents problems connected to the need to correctly reproduce the band gap of the material and the localized nature of the defects created by doping.

Dr. Yoshitaka Tateyama(館山佳尚)