Abstract
In this research, highly thermal stable and phase-pure anatase titanium dioxide was synthesized by a microwave-assisted hydrothermal method (MAH method). Titanium ion (IV) in aqueous sulfuric acid solution was used as precursor for sample preparation. After sufficient ultrasonic treatment and stirring, the solution was heated to 200OC for 20 minutes by a microwave reactor. The as-prepared sample was washed by D.I. water for several times to remove residual impurities and then calcined at various temperatures in the air for 2 hours. Finally, the sample was ground to powder and white titanium dioxide nanoparticles (TiO2-NPS) were obtained. The material analysis such as structures, phases, crystalline sizes, band gaps, band structures, electron-hole recombinations, morphologies, and pore structures were characterized by means of X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), photoluminescence (PL), scanning electron microscopy (SEM), transmission electron microscope (TEM), and N2 adsorption- desorption analysis. Moreover, the photoelectrochemical behavior such as photocurrent density, electron transport time and electron lifetime were studied via linear sweep IV voltammetry (LSV), intensity modulated photocurrent spectroscopy (IMPS), and intensity modulated photovoltage spectroscopy (IMVS). In order to investigate the photocatalytic activity of the as-prepared and calcined TiO2-NPS at various temperatures. The samples were suspended directly and also by coating on the graphite electrode under methylene blue which was used as pollutant. The photodegradation system was operated under simulated sun light. The result shows that phase-pure anatase titanium dioxide can be synthesized by a simple, time and energy saving MAH method. Besides, the photocatalytic activity was enhanced with an increase of calcined temperature. The sample calcined at 800OC exhibits faster degradation rate compared with commercially available Degussa P25 when the suspension was applied. On the other hand, the sample coated on the graphite electrode lost some effective surface area, but still possesses comparable photocatalytic activity with Degussa P25. The higher photocatalytic activity was obtained due to the better crystallinity, lower recombination of electron-hole pair and larger photocurrent density. Keywords: TiO2; Microwave-assisted hydrothermal method; Thermal stability; Photocatalysis