Contatto di riferimento: Marta Tessarolo
Partecipanti: Dr. Alberto Piccioni
TiO2, especially in the form of nanoparticles (NPs) or nanostructured thin films (NTFs), has become one of the most studied wide band gap oxide semiconductors due to its photocatalytic properties, opening the way to various applications such as hydrogen production from water, environmental cleaning (air and water), fabrication of dye sensitized solar cells and others. However, because of its wide band gap (3.2 eV), only a small fraction of the solar spectrum, i.e. UV light (3-5% of total), can be used for photocatalytic processes.
A widely investigated strategy to shift the optical absorption of TiO2 towards the visible region is doping with ionic species. The absorption red-shift arise from creation of
intra-gap localized dopant levels. However, the enhanced optical absorption does not necessarily correspond to the achievement of photocatalytic activity in a previously inactive spectral range.
Although several theoretical and experimental studies on doped photocatalysts have been published, a clear mechanistic view of the dopant role on photocatalytic behavior is far from being established.
Here I will remark that Vanadium doping can influence TiO2 photocatalysis by enhancing the optical absorption in the visible range, and generating photoexcited reactive species that possess suitable redox potentials for water splitting and other photocatalytic reaction.
The technique employed to study the charge carrier dynamic is transient absorption spectroscopy with sub 100 fs time resolution. The peculiar TA features of undoped and V-doped TiO2 NPs are correlated to their photoactivity at different excitation wavelengths. I will show that V-doped TiO2 NPs exhibit a clear photoactivity, both for nitro group reduction and for photoelectrochemical water splitting, in the visible spectral range (450 nm) where undoped TiO2 is completely inactive.