Abstract
V-TiO2 photocatalyst with 0 ≤ V ≤ 20 mol% was prepared via the sol–gel method based on mixed oxide titanium–vanadium nanoparticles with size and composition control. The mixed oxide vanadium–titanium oxo-alkoxy nanonoparticles were generated in a chemical micromixing reactor, coated on glass beads via liquid colloid deposition method and underwent to an appropriate thermal treatment forming crystallized nanocoatings. X-ray diffraction, Raman, thermogravimetric and differential thermal analyses confirmed anatase crystalline structure at vanadium content ≤ 10 mol%, with the cell parameters identical to those of pure TiO2. At a higher vanadium content of ~20 mol%, the material segregation began and orthorhombic phase of V2O5 appeared. The crystallization onset temperature of V-TiO2 smoothly changed with an increase in vanadium content. The best photocatalytic performance towards methylene blue decomposition in aqueous solutions under UVA and visible light illuminations was observed in V-TiO2 nanocoatings with, respectively, 2 mol% and 10 mol% vanadium.
Highlights
The current high level of environmental pollution by toxic contaminants requires the development of an effective decontamination processes, a field in which photocatalysis has attracted particular interest [1,2,3]
As we showed recently [37], at a relatively low V content of ≤20 mol%, the vanadium–titanium oxo-alkoxy (VTOA) nanoparticles are formed via condensation of titanium oxo-alkoxy (TOA) species, which attract hydrolyzed vanadium species at the surface
In order to keep the material in the most photocatalytically efficient anatase crystalline phase, the vanadium content in these studies was limited to 20 mol%
Summary
The current high level of environmental pollution by toxic contaminants requires the development of an effective decontamination processes, a field in which photocatalysis has attracted particular interest [1,2,3]. Hair dye [4], leather and paper industries [5] and luminescent solar concentrator (LSC) technologies [6] use a large amount of organic dyes potentially associated with water pollution In this context, titanium dioxide (TiO2) became the key material [7,8] showing high effectiveness in the pollutants’ decomposition, whose activation is, limited by the ultraviolet (UV) spectral range hν > Eg = 3.2 eV of anatase crystalline phase. Liu et al [30] have drawn attention to the problem of the composition homogeneity of V-TiO2 materials; they suggested that the photocatalysts doped by vanadium unevenly with a p–n junction semiconductor structure have much higher photocatalytic activity than pristine and evenly doped TiO2 and ascribed this result to the electrostatic-field-driven electron-hole separation These authors have observed the activity enhancement at a very low level of ~0.002 mol% V. We notice that this low value of optimal doping can be connected to the compositional homogeneity; it is characteristic of the materials with different mobilities of photoexcited electron and hole and can be explained by a competition between charge localisation and annihilation processes on the inserted cations [31]
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