Preparation Of Titanium Oxide With Different Phase Composition And Enhanced Visible Light Catalytic Properties By Assembly

In this paper we use tetrabutyl titanate as precursor, with ethanol as the solvent, tosynthesize TiO₂crystals from neutral and alkaline systems, respectively. Throughchanging the volume of nitric acid solution, the phase composition of TiO₂could besuccessfully controlled. As a result, four samples with different phase compositionwere obtained, such as pure rutile phase, rutile-dominant composite,anatase-dominant composite and pure anatase phase. On this basis, we assembled theindividual TiO₂crystals from neutral and alkaline systems via an ethanol evaporationinduced self-assembly （EISA） processs. Such dopant-free assemblies formed byinterfacial Ti–Ti electronic bonding have a narrower bandgap than individualnanocrystals, which improved the photocatalytic property of pure TiO₂under visiblelight.For the TiO₂samples obtained from neutral and alkaline systems as well as thesamples after surface self-assembling, we used XRD, TEM, SEM, UV-Vis, EDS,FTIR, Raman techniques to characterize and analyze the phase composition, the size,the morphology before and after assembly, the change in energy band gap, thechange in element proportion, the changes in structure and phase composition. In thispaper, the visible light photocatalytic activities of assemblied TiO₂samples wereevaluated and compared using methylene blue solution as target pollutant undervisible light irradiation for4h. Finally, we introduced EPR technique to detect thehydroxyl radical during photocatalytic reaction and the change in amount with theirradiation time.For the neutral system, we studied the influence of the phase composition of TiO₂,the number of rotary evaporation, and the self-assembly time at100°C on the visiblelight photocatalytic activity of crystals after surface modification. In addition, SnOcrystals were incorporated into pure anatase TiO₂to the formation of compositephotocatalyst. The recombination rate of electrons and holes as well as the hydroxylradicals were investigated by PL and EPR techniques. Thus the influence of SnOincorporation on the photocatalytic property of pure anatase TiO₂was studied.Meanwhile, the TiO₂crystals from alkaline system were assembled together viaEISA processs. We studied the influence of the phase composition of TiO₂, thenumber of rotary evaporation, and the self-assembly time at100°C on the visiblelight photocatalytic activity of assembled crystals after surface modification.