ABSTRACT
A series of TiO2 with different crystal phases and morphologies was synthesized via a facile hydrothermal process using titanium n-butoxide and concentrated hydrochloric acid as raw materials. The photocatalytic activity of the samples was evaluated by degradation of Methyl Orange in aqueous solution under UV-Visible light irradiation. On the basis of detailed analysis of the characterizing results of high-resolution transmission electron microscopy, X-ray powder diffraction measurements, X-ray photoelectron spectroscopy and Brunauer-Emmett-Teller measurement, it was concluded that the photo-activity of the catalyst is related directly to the 3D morphology and the crystal phase composition. An excellent catalyst should have both a rutile 3D flower-like structure and anatase granulous particles. The 3D flower-like structure could enhance light harvesting, as well as the transfer of reactant molecules from bulk solution to the reactive sites on TiO2. In addition, the optimum anatase/rutile phase ratio was found to be 80:20, which is beneficial to the effective separation of the photogenerated electron-hole pairs.
Subject(s)
Nanoparticles/chemistry , Nanotubes/chemistry , Photolysis , Titanium/chemistry , Azo Compounds , Catalysis , Microscopy, Electron, Transmission , Nanoparticles/radiation effects , Nanotubes/radiation effects , Photoelectron Spectroscopy , Sunlight , Titanium/radiation effects , X-Ray DiffractionABSTRACT
Semiconducting silver iodate (AgIO(3)) was used to modify the visible light response of an AgI/TiO(2) (AIT) catalyst by a facile method. The uncalcined AIT (AITun) and AIT calcined at 200°C (AIT200) consisted of AgIO(3), AgI, and TiO(2) semiconductors, while that calcined at 450 °C (AIT450) was composed of AgI and TiO(2). The activity in p-chlorophenol (PCP) degradation under visible light irradiation using either AITun or AIT200 was much higher than that with AIT450, which was mainly attributed to the fact that the presence of AgIO(3) provided a new matching band potential. AIT200 exhibited better photocatalytic properties than AITun due to its higher crystallinity after calcination. Moreover, the high catalytic activity of AIT200 was maintained after five successive cyclic experiments under visible irradiation. Considering the effect of radical scavengers and N(2) purging on the photocatalysis process, we deduced that the probable pathway of PCP degradation was mainly a surface charge process, caused by valence band holes.