Synthesis, characterization and evaluation of the photocatalytic properties of WO₃ obtained through the polyol method

ABSTRACT

This work shows a synthetic route mediated by tetraethylene glycol (P. E. 325 ° C) in which tungstic acid is used as the starting material. The formation of a stable blue suspension was observed during the course of the reaction. The size of the particles depends on the synthesis time, and particles of size around 400 nm were obtained after 15 minutes of reaction in tetraethylene glycol. The particulate materials were then annealed at different temperatures: 150 °, 350 ° C, 500 ° C and 800 ° C, and characterized by TGA / DSC, DRX, FT-RAMAN, MEV, UV-VIS optical spectroscopy and N₂ adsorption at 77K. It was observed that the synthesis provided WO3 under orthorhombic phase that evolved to monoclinic after heat treatment at a temperature equal to or greater than 350 ° C. The morphological characterization indicated the formation of ovoids particles when treated at temperatures around 500 ° C, a temperature from which the surface area decreases dramatically. The photocatalytic activity for the degradation of rhodamine B (rhB, 10 mg.L^-1) was evaluated under ultraviolet irradiation (6 Watts). Greater activity was found for the material treated at 500 ° C, with total discoloration after 180 minutes in the presence of 10 mg of this catalyst.

Keywords
Tungsten trioxide; Rhodamine B; Photocalysis; Polyol method