Aijian Wang

Novel Bi2O2CO3/polypyrrole/g-C3N4 nanocomposites with efficient photocatalytic and nonlinear optical properties

Semiconductor nanostructures perform wide applications in light-driven physical and chemical processes; in particular, nanomaterials based on Bi2O2CO3 with tunable photophysical properties have attracted intense interest. However, the nonlinear optical properties and photocatalytic performances of the ternary system Bi2O2CO3/polypyrrole/g-C3N4 have not been reported. In this paper, a series of novel Bi2O2CO3/polypyrrole/g-C3N4 nanocomposites loaded with different g-C3N4 contents was prepared to maximize the photocatalytic activity and optical nonlinearity. The structure, composition and morphology of the as-prepared samples were characterized by Fourier-transform infrared spectroscopy, X-ray powder diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The wide absorption of the samples in the visible light region makes them suitable for photocatalytic and nonlinear transmission studies. Their photocatalytic performances were evaluated by degradation of rhodamine B. The associated photocatalytic activity of Bi2O2CO3/polypyrrole/g-C3N4 nanocomposites is shown to be dependent on the g-C3N4 loading. Compared to Bi2O2CO3, PPy, g-C3N4, BP and B/C0.5, the BP/C0.5 composite with 0.5 wt% g-C3N4 exhibits the highest photocatalytic activity. The nonlinear optical properties were investigated by open-aperture Z-scan measurements at 532 nm with 4 ns laser pulses. The results demonstrated that the BP/C0.5 composite exhibited improved properties for photocatalysis and optical nonlinearity, which is ascribed to a combination of mechanisms.

Facile synthesis and photocatalytic activity of a novel titanium dioxide nanocomposite coupled with zinc porphyrin

To improve the photocatalytic activity of titanium dioxide, a novel nanocomposite was prepared via axial coordination of zinc porphyrin on the semiconducting titanium dioxide surface modified with axial coordinating ligand functionality, pyridine. The obtained product (zinc porphyrin/titanium dioxide) was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, fluorescence, thermogravimetric analysis, and Raman spectroscopic techniques. The photocatalytic performance of the samples was investigated by photodegradation of rhodamine B in aqueous solution. The attached zinc porphyrin on the surface can act as a small bandgap semiconductor to absorb visible light, resulting in the formation of electron–hole separation and an improved photocatalytic activity for the nanocomposite.

The Role of Lewis and Brønsted Acid Sites in NO Reduction with NH 3 on Sulfur Modified TiO 2 -Supported V 2 O 5 Catalyst

V2O5/S-doped TiO2 was prepared by the sol-gel and impregnation methods. The adsorption of NO, NH3, and O2 over the catalyst was studied by in situ DRIFTS spectroscopy to elucidate the reaction mechanism of the low-temperature selective catalytic reduction of NO with NH3. Exposing the catalyst to O2 and NO, three types of nitrates species appeared on the surface. The introduction of S to TiO2 could generate large amounts of acid sites for ammonia adsorption on the catalyst, which was believed to be an important role in the SCR reaction and hereby improved the catalytic activity. The results indicated two possible SCR reaction pathways for catalyst. One was that NO was absorbed to form nitrite species, which could react with NH3 on Lewis acid sites, producing N2 and H2O. Another way was that NH3 was adsorbed, then reacted with gas phase NO (E–R) and nitrite intermediates on the surface (L–H).