Spectroscopic and diffractometric study of the V2O5/TiO2 system prepared via mechanochemical activation

Materials consisting of a vanadium oxide (VOx) phase dispersed on a TiO2 matrix and obtained by mechanochemical activation of the V2O5 and TiO2, are compared with materials obtained by high temperature solid state reaction between the same two oxides. As a consequence of grinding, a non-negligible formation of isolated VIV is evidenced by EPR, whose nature is typically vanadylic (VO2+). Diffuse reflectance UV-VIS spectroscopy indicates that the reduction of the dispersed phase also induces the formation of more reduced vanadium species like VIII. Various distinct VO2+ species are stabilized on the surface by thermal treatments, and their coordinative environment has been tested by adsorption of NH3 and H2O. The phase changes brought about in the TiO2 matrix by the grinding process as well as the presence of crystalline V2O5 have been monitored by XRD.