Frank S. C. Lee

Fabrication of Bi-Doped TiO 2 Spheres with Ultrasonic Spray Pyrolysis and Investigation of Their Visible-Light Photocatalytic Properties

Bismuth-doped TiO2 submicrospheres were synthesized by ultrasonic spray pyrolysis. The prepared bismuth-doped titania was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (UV-vis DRS), and X-ray photoelectron spectroscopy (XPS). Aqueous photocatalytic activity was evaluated by the decomposition of methyl orange under visible-light irradiation. The results indicate that doping of bismuth remarkably affects the phase composition, crystal structure, and the photocatalytic activity. The sample with 2% Bi exhibits the optimum photocatalytic activity.

Template-free synthesis of ternary sulfides submicrospheres as visible light photocatalysts by ultrasonic spray pyrolysis

CdIn2s4, ZnIn2S4 and AgIn5S8 were prepared by ultrasonic spray pyrolysis method without using templates which demonstrated a general route for the synthesis of ternary sulfides submicrospheres.

Advances in the Fine Scale Simulation of Urban Wind Environment

This work gives a review of studies on the air flow and pollutant dispersion in the fine scale environment of the urban street canyon. The affecting factors on the air flow and pollutant dispersions in urban street canyons are illustrated by analyzing the street canyon physical model and boundary conditions. The building layouts along the street and the variations in the ambient wind velocities and directions could contribute an impact on the basic air flow within urban street canyons, while the atmospheric instabilities inside the street canyons, the vehicle induced turbulence, and tree plantings could affect the turbulence and pollutant distributions inside the street canyons, especially under weak-wind conditions. In the case of the street canyons with high aspect ratio (building height H over street width W), Reynolds number would be related to the vortex structure. The current empirical or semi-empirical models are lacking of careful description of the street canyon’s real geometries and atmospheric conditions, which had often resulted in large errors in the simulated or forecasted results. Based on the computational fluid dynamic (CFD) method, further development of numerical models should focus on the integrated model, taking account of canyon’s real geometries and the real atmospheric conditions.

Efficient visible light photocatalytic oxidation of NO on F- and N-codoped spherical TiO 2 synthesized via ultrasonic spray pyrolysis

The fluorine- and nitrogen-codoped TiO2 was synthesized by ultrasonic spray pyrolysis method with titanium tetrafluoride and urea as precursor. The codoped TiO2 was characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS). Nitric oxide (NO) photocatalytic oxidation in gas-phase medium was employed as a probe reaction to evaluate the photocatalytic reactivity of the catalysts. The results indicated that spherical codoped TiO2 photocatalysts with unique puckered surface were obtained by this method. The codoped catalysts have solely anatase crystalline structure. The optical characterization of the codoped catalysts showed that the codoped samples could be excited by visible light photons in the 400-550nm and could efficiently oxidize NO under visible light irradiation. The mechanism of special morphology formation of prepared codoped TiO2 structure is also discussed.