Síntese e avaliação da atividade fotocatalítica de compósitos nanoestruturados de TiO2/SiO2

Abstract

In the presente work, silicone dioxide (SiO2) covered by a layer of titanium dioxide(TiO2) was synthesized by sol-gel process, with the aim of developing semiconductive oxides with the improved photocatalytic activity, for the application in photocatalytic process. Silica (SiO2) coating was proven by scanning electron microscopy and infrared measurements. X-ray diffraction meansurements revealed that the TiO2 nanoparticles was predominantly formed by anatase phase. The photocatalytic efficiancy of the material was proven by the degradation of the dye Ponceau 4R. About 100% of the dye was discolored in 140 minutes of reaction, at a kinetic degradation constant (K) of 2,2 x 10-2 min-1, within the first 80 minutes of reaction, and K = 5,2 x 10-2 min-1, within the last 60 minutes of reaction, suggesting that in this second stage the fragments are more easily descolored. Bench scale photocatalytics tests were also performed, in the presence of platinum, aiming to evaluate the hydrogen production capacity, resulting in the production of 5,463 mmol of H2 in 5 hours of reaction. A very significant value when compared to other photocatalysts presented in the literature, and coherent with the surface area of 70 m2 g-1, estimated by N2 adsorption / desorption measurements by the BET method, and porosity of 15%. On the other hand, band gap energy (Eg) estimated for this material, equal to 3,34 eV, may be related to the association between electronic states of SiO2 and TiO2 in the composite. Thus, the TiO2/SiO2 nanocomposite presents high potential for application in photocatalytic processes, especially in the production of hydrogen.