Qizhe Fan

Sonochemical fabrication of novel square-shaped F doped TiO2 nanocrystals with enhanced performance in photocatalytic degradation of phenol

A sonochemical method was developed for the fabrication of novel square-shaped TiO(2) nanocrystals doped with different F contents. The prepared samples were characterized by some physicochemical characterizations like X-ray diffraction (XRD), N(2) physical adsorption, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrum (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy and UV-vis diffuse reflectance spectra (DRS). Phenol, as a hazardous chemical in water, was chosen to evaluate the photocatalytic degradation performance of the prepared TiO(2) nanocrystals under UV light irradiation. Results show that under ultrasonic irradiation conditions, F can easily be doped into TiO(2) and the obtained pure and F doped TiO(2) nanocrystals show mesoporous structures which were formed by the role of ultrasound-induced aggregation. Moreover, the doping of optimal content of F (1.3 mol%) gives 5.3 times increase in the phenol degradation rate. The high photocatalytic degradation activity of the doped TiO(2) could be attributed to the factor that F doping increases the surface hydroxyl groups over TiO(2) and effectively reduces the recombination rate of photo-generated electron/hole pairs, then producing more OH radicals to decompose the phenol molecules.

Ultrasonic fabrication of N-doped TiO2 nanocrystals with mesoporous structure and enhanced visible light photocatalytic activity

An ultrasonic method was developed to fabricate novel mesoporous TiO2 nanocrystals doped with a high concentration of N (N/TiO2). The nanocrystals were characterized by physicochemical methods including N2 physical adsorption/desorption, X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, transmission electron microscopy, and UV-Vis diffuse reflectance spectroscopy. The photocatalytic degradation of dimethyl phthalate, a hazardous chemical in water, by the prepared N/TiO2 nanocrystals under visible light irradiation (400–660 nm) was investigated. The results show that N-doping efficiency under ultrasonic irradiation is 3.2 times higher than under typical conditions, and the produced TiO2 nanocrystals have mesoporous structure. N/TiO2 fabricated under ultrasound exhibited much higher efficiency for the degradation of dimethyl phthalate than that prepared under typical conditions. The high photocatalytic degradation activity of N/TiO2 fabricated under ultrasound is mainly attributed to its high N content effectively increasing its ability to absorb visible light.

Novel Ni/CeO2-Al2O3 composite catalysts synthesized by one-step citric acid complex and their performance in catalytic partial oxidation of methane

Abstract A series of novel Ni/CeO 2 -Al 2 O 3 composite catalysts were synthesized by one-step citric acid complex method. The as-synthesized catalysts were characterized by N 2 physical adsorption/desorption, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, hydrogen temperature-programmed reduction (H 2 -TPR), X-ray photoelectron spectroscopy (XPS) and thermogravimetry analysis (TGA). The effects of nickel content, calcination and reaction temperatures, gas hourly space velocity (GHSV) and inert gas dilution of N 2 on their performance of catalytic partial oxidation of methane (CPOM) were investigated. Catalytic activity test results show that the highest methane conversion (>85%), the best selectivities to carbon monoxide (>87%) and to hydrogen (>95%), the excellent stability and perfect H 2 /CO ratio (2.0) can be obtained over Ni/CeO 2 -Al 2 O 3 with 8 wt% Ni content calcined at 700 °C under the reaction condition of 750 °C, CH 4 /O 2 ratio of 2 : 1 and gas hourly space velocity of 12000 mL·h −1 ·g −1 . Characterization results show that the good catalytic performance of this composite catalyst can be contributed to its large specific surface area (∼108 m 2 ·g −1 ), small crystallite size, easy reducibility and low coking rate.

Preparation, characterization and photocatalytic performance of heterostructured AgCl/Bi2WO6 microspheres

Bi2WO6 microspheres with a diameter of 1.5–2 μm were prepared by a hydrothermal method, and then coated with different contents of AgCl to form heterostructured AgCl/Bi2WO6 microspheres. The prepared Bi2WO6 and AgCl/Bi2WO6 photocatalysts were characterized by X-ray diffraction, N2 physical adsorption, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy. The photocatalytic activity of the catalysts was evaluated by photocatalytic degradation of rhodamine B under ultraviolet and visible light irradiation. Results showed that the deposition of AgCl had no obvious effect on the light absorption and surface properties of Bi2WO6. However, the heterostructured AgCl/Bi2WO6 photocatalysts exhibited considerably higher activity than the pure AgCl and Bi2WO6 catalysts. With the optimal AgCl content of 20 wt%, the photocatalytic activity of the heterostructured AgCl/Bi2WO6 catalyst was increased under both ultraviolet and visible light compared with that of Bi2WO6. The main reason for the enhanced photocatalytic activity is attributed to the formation of AgCl/Bi2WO6 heterostructures effectively suppressing the recombination of photogenerated electrons and holes.

La/Ce-codoped Bi2O3 composite photocatalysts with high photocatalytic performance in removal of high concentration dye

A series of La/Ce-codoped Bi2O3 composite photocatalysts were fabricated via hydrothermal-calcination process. The as-prepared products were intensively characterized by some physicochemical characterizations like N2 physical adsorption, X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), UV-Vis diffuse reflectance (UV-Vis DRS), Fourier transform infrared spectroscopy (FT-IR), photoelectrochemical measurements, and photoluminescence (PL) spectroscopy. The characterization results indicated that La and Ce doping induced obvious crystal phase transformation in Bi2O3, from monoclinic to tetragonal phase. La and Ce codoping also gave rise to the obvious synergetic effects, e.g., the lattice contraction of Bi2O3, the decrease of crystal size and the increase of surface area. The photocatalytic performance of the prepared catalysts was evaluated by removal of dye acid orange II with high concentration under visible light irradiation. Results showed that La/Ce-codoped Bi2O3 displayed much higher photocatalytic performance than that of bare Bi2O3, single La or Ce doped Bi2O3 samples. The superior photocatalytic activity was mainly attributed to the improved texture and surface properties and the synergistic effects of La and Ce codoping on suppressing the recombination of photo-generated electrons (e-) and holes (h+).