Jiali Wen

One-step synthesis of N- and F-codoped mesoporous TiO2 photocatalysts with high visible light activity

We report on a novel approach to the synthesis of N- and F-codoped mesoporous TiO2 photocatalysts via a reproducible, rapid and single-step combustion method. TiF4 was used as the precursor to provide the source of Ti and F, while urea was used as the fuel as well as the source of the N dopant. The as-synthesized samples were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS) and UV-vis spectroscopy. The specific surface areas of the samples were determined using a Quantachrome Nova 2200 for the N2 adsorption/desorption under liquid-nitrogen temperature. Our studies show that the fabricated N- and F-codoped TiO2 photocatalysts have mesoporous structure and a very large specific surface area (155.3 m(2) g(-1)) and that the codoping of N and F significantly narrows the TiO2 bandgap energy from 3.2 to 2.45 eV. We further studied the photocatalytic activity of the synthesized N- and F-codoped mesoporous TiO2 through the decomposition of acetic acid, showing that the N- and F-codoped mesoporous TiO2 catalyst fabricated in this study exhibits superb photocatalytic activity and visible light response compared to one of the best commercially available TiO2 photocatalysts, P25.

Facile synthesis of mesoporous carbon nitride and titanium dioxide nanocomposites with enhanced visible light photocatalytic activity

A facile and efficient solution combustion method was developed and employed in the fabrication of novel mesoporous carbon nitride and titanium dioxide (C3N4–TiO2) nanocomposites as advanced photocatalysts for wastewater remediation. Urea was used as the precursor of C3N4, while titanium tetra-isopropoxide served as the source of titanium. Yellow nanocomposites were produced as compared to the formed white TiO2 and C3N4 nanomaterials. Transmission electron microscopic images and N2 adsorption/desorption analysis revealed that the fabricated nanocomposites possessed a mesoporous structure and much larger surface areas as compared to the individual constituents. X-ray photoelectron spectroscopic measurements and thermogravimetric analysis were utilized to determine the composition and thermal stability of the C3N4–TiO2 nanocomposites. Tauc plots derived from the UV-vis absorption spectra revealed that the formation of the C3N4–TiO2 nanocomposites significantly narrowed the band gap energy, leading to a high visible light response in contrast to the individual TiO2 (∼3.2 eV) and C3N4 (∼2.8 eV) samples. The optimal composition of the C3N4–TiO2 nanocomposites was determined, and the new nanocomposite developed in this study exhibited high visible light activity in the photochemical oxidation of Rhodamine B, as compared to the mechanically mixed C3N4 and TiO2 sample. This significant improvement in photocatalytic activity may be attributed to the synergistic effects of the red shift in absorption and the large surface area.

Unique copper and reduced graphene oxide nanocomposite toward the efficient electrochemical reduction of carbon dioxide

The electrochemical reduction of CO2 to useful chemicals and fuels has garnered a keen and broad interest. Herein, we report a unique nanocomposite consisting of Cu nanoparticles (NPs) and reduced graphene oxide (rGO) supported on a Cu substrate with a high catalytic activity for CO2 reduction. The nanocomposite was optimized in terms of the composition of Cu NPs and rGO as well as the overall amount. A gas chromatograph was employed to analyze the gaseous products, whereas a chemical oxygen demand (COD) method was proposed and utilized to quantify the overall liquid products. The optimized nanocomposite could effectively reduce CO2 to CO, HCOOH and CH4 with a Faradaic efficiency (FE) of 76.6% at −0.4 V (vs. RHE) in a CO2 saturated NaHCO3 solution. The remarkable catalytic activity, high FE, and excellent stability make this Cu-rGO nanocomposite promising for the electrochemical reduction of CO2 to value-added products to address the pressing environmental and energy challenges.