Estudo da influência do tratamento térmico na atividade fotocatalítica de semicondutores baseados nos óxidos de Titânio (IV) e Tungstênio (VI).

Abstract

This work had the aim to study the influence of thermal treatment in the morphological and photocatalytic properties of TiO2 and WO3-TiO2, in molar ratios of 1:4 and 1:40 (W:Ti). It is known that thermal treatment influences directly in parameters such as crystallinity phase and grade, porosity and surface area, which are directly related with the photocatalytic efficiency of these materials. The oxides where obtained by the sol-gel method, followed by hydrothermal treatment. After, the oxides where calcinated in an oven in different temperatures and times of calcination. The conditions of the thermal treatment for the WO3-TiO2 where stablished after the results with TiO2 where obtained. The materials where characterized by Xray diffractometry, surface area by the B.E.T. method and scanning electron microscopy. Methanol photo-oxidation tests under UV-A irradiation (315-380 nm) where run to evaluate the photocatalytic activity. The formation of formaldehyde over irradiation time was monitored using the Nash method. The oxide which had the best photonic efficiency was the TiO2 calcinated in 600 °C for 30 minutes (7,55 ± 0,36 %). Among the WO3-TiO2, the best result was obtained with the composite 1:40 calcinated in 700 °C (1,50 ± 0,15 %). It was observed that for TiO2 the mixed crystal phases anatase-broquite and anatase-rutile contributed to a good material’s performance, as well as the increase in calcination temperature till 600 ºC. The increase in calcination time, however, decreased the photonic efficiency. For WO3-TiO2, the increase in calcination temperature was prejudicial for material’s performance.