Effect of Vacuum-Sealed Annealing and Ice-Water Quenching on the Structure and Photocatalytic Acetone Oxidations of Nano-TiO2 Materials.

Abstract

In the current research, P25 TiO2 materials sealed in quartz vacuum tubes were subject to annealing and ice-water post-quenching, with the effects on TiO2 structures, morphology, and photocatalytic activity being studied. It is shown that the vacuum-sealed annealing can lead to a decrease in the crystallinity and temperature of anatase-to-rutile phase transition. A disorder layer is formed over TiO2 nanoparticles, and the TiO2 lattices are distorted between the disorder layer and crystalline core. The ice-water post-quenching almost has no effect on the crystalline structure and morphology of TiO2. It can be seen that the vacuum-sealed annealing can generate more defects, and the electrons are mainly localized at lattice Ti sites, as well as the percentage of bulk oxygen defects is also increased. Although further ice-water post-quenching can introduce more defects in TiO2, it does not affect the electron localization and defect distribution. The vacuum-sealed annealing process can increase the photocatalytic acetone oxidations of the anatase phase TiO2 to some extent, possibly because of the defect generation and Ti3+ site formation; the further ice-water quenching leads to a decrease in the photocatalytic activity because more defects are introduced.