Effective Inclusion of Sizable Amounts of Mo within TiO2 Nanoparticles Can Be Obtained by Reverse Micelle Sol-Gel Synthesis.

Abstract

Six Mo/TiO2 samples (with 0, 1.0, 2.5, 5.0, 7.5, and 10 wt % Mo nominal contents) were obtained by reverse micelle sol–gel synthesis, followed by calcination at 500 °C. The samples were characterized by means of powder X-ray Diffraction (PXRD), quantitative phase analysis as obtained by Rietveld refinement, field-emission scanning electron microscopy (FE-SEM) coupled with energy-dispersive X-ray analysis, N2 adsorption/desorption at −196 °C, X-ray photoelectron spectroscopy, and diffuse reflectance (DR) UV–vis spectroscopy. As a whole, the adopted characterization techniques showed the inclusion of a sizeable Mo amount, without the segregation of any MoOx phase. Specifically, PXRD showed the occurrence of anatase and brookite with all the studied samples; notwithstanding the mild calcination temperature, the formation of rutile occurred at Mo wt % ≥2.5 likely due to the presence of brookite favoring, in turn, anatase to rutile transition. DR UV–vis and XP spectroscopies allowed determining the samples’ band gap energy (Eg) and valence band energy, respectively, from which the conduction band energy was calculated; and the observed Eg value increase at 10 wt % Mo was ascribed to the Moss–Burstein effect.