Positron annihilation study of structural effect on photocatalytic activity of mesoporous TiO2 thin films

Mesoporous TiO2 films were synthesized by using triblock copolymers via a sol-gel process in aqueous solution. It was found that a film calcined at 600 °C has the highest photocatalytic activity. By application of positron annihilation Doppler broadening spectroscopy combined with XRD, SEM, and N2 adsorption desorption techniques, the film structural properties were examined systematically. It is revealed that an excellent photocatalytic activity could be achieved only if a film maintains a suitable TiO2 grain size, i.e. ∼7.5 nm in the present study, a median specific surface area and a high crystallinity in anatase state.