Introduction of peroxo groups into titania: preparation, characterization and properties of the new peroxo-containing phase
A new phase, where peroxo groups are incorporated into titania particles, along with anatase and hydrated η-TiO2 with peroxo groups on the surface of titania nanoparticles were prepared by introduction of H2O2 into reaction mixtures while synthesizing TiO2 from TiOSO4 or by cold impregnation of pre-synthesized TiO2. The samples were studied by a range of methods (classical and synchrotron-radiation X-ray powder diffraction, small-angle X-ray scattering, high-resolution scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray absorption spectroscopy, IR and Raman spectroscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance and absorption spectroscopy, DSC). The [TiOx(O2)2−x(H2O)m] phase was first structurally characterized and compared to η-TiO2. Most samples of H2O2-sensitized TiO2 discolor methyl orange under visible light irradiation faster than commercial Hombikat UV100 treated with H2O2. The activity of the samples strongly relating to their phase composition was associated with the existence of a large amount of titanium peroxo complexes along with formation of mixed-phase samples.