Photocatalytic Materials Based on F-doped or codoped TiO2

The photocatalytic activity of an extended series of singly doped or co-doped TiO2 photocatalysts prepared by the sol-gel method starting from different amounts of N, F, S and B dopants and calcined at different temperatures in the 500-700 °C range, was investigated, also as a function of the irradiation wavelength, in both thermodynamically down-hill reactions (formic and acetic acid degradation in aqueous suspension, gas phase mineralization of acetaldehyde) and up-hill reactions for solar fuels production (H2 production from methanol-water vapor mixtures). By comparing the absorption spectra of the materials with their action spectra in acetic acid oxidation, inactive light absorption, i.e. not leading to any photocatalytic reaction, could be clearly distinguished from effective photoactivity. An in depth HRTEM analysis provided novel information on the peculiar effects that fluorine doping has on the bulk structure of these materials. Time resolved photo-luminescence (PL) analysis in the pico-second range revealed that both PL spectral shapes and lifetimes are strongly affected by the presence of dopants and by the calcination temperature, and that a correlation exists between the longer-living luminescence component and the photocatalytic activity of the materials.