Optical and photocatalytic properties of titanium–manganese mixed oxides

Nanocrystalline titanium–manganese mixed oxides (TMMO) with Mn content of 13–16 at.% were first synthesized by manganese hydroxide precipitation on anatase or rutile particles. The structure, morphology and chemical composition of the samples were characterized using XRD, SEM, EDS and XRF methods showing that the synthesized mixed oxides are polydisperse materials of different phase compositions containing TiO2, Mn2O3 and MnTiO3. The defect structure and phase formation of the prepared compounds were characterized by FTIR, FT-FIR, FT-Raman spectroscopies. UV–vis absorption spectra were investigated in 2.4–6.0 eV region and revealed that compared with pure TiO2 the presence of manganese oxides results in an increase of the absorption intensity and significant red shift of the TMMO absorption edge. Photocatalytic activity of pure TiO2, Mn2+-doped TiO2 and TMMO during the photocatalytic decomposition of the safranine dye under UV irradiation was studied. A great improvement of photocatalytic activity is registered for Mn2+-doped TiO2 (anatase and rutile), and rutile-based TMMO sample.