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

Abstract

Materials consisting of a vanadium oxide (VO_x) 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 V^IV 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 V^III . 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 V₂O₅have been monitored by XRD.