Darui Liu

Photocatalytic degradation of an azo dye using N-doped NaTaO3 synthesized by one-step hydrothermal process.

N-doped NaTaO(3) compounds (NaTaO(3-)(x)N(x)) with nano-cubic morphology were successfully synthesized by one-step hydrothermal method and Methyl Orange (MO) was used as a model dye to evaluate their photocatalytic efficiency under visible-light irradiation. The as-prepared NaTaO(3-)(x)N(x) samples were characterized by various techniques, such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectra and GC-MS. The results indicate that NaTaO(3-)(x)N(x) displays a pure perovskite structure when the synthesis temperature is higher than 180°C. Moreover, as observed by SEM images, the particles of resultant NaTaO(3-)(x)N(x) show cubic morphology with the edge length of 200-500nm, which can be easily removed by filtration after photocatalytic reaction. Doping of N increases the photocatalytic activity of NaTaO(3), and NaTaO(2.953)N(0.047) shows the highest visible-light photocatalytic activity for the degradation of MO. Based on the experiment results, a possible mechanism of the photocatalysis over NaTaO(3-)(x)N(x) and the photodegradation pathway of MO were proposed.

Synthesis and photocatalytic activity of N-doped NaTaO3 compounds calcined at low temperature.

N-doped NaTaO(3) compounds (NaTaO(3-x)N(x)) were successfully synthesized using NaTaO(3) prepared at low calcination temperature as starting material and melamine (C(3)H(6)N(6)) as nitrogen source. The as-prepared NaTaO(3-x)N(x) samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectra. The XRD results indicate that the crystallization temperature of NaTaO(3) is up to 700 degrees C and the doping of N does not lead to significant structural changes. Moreover, as observed by SEM images, the particle sizes of resultant NaTaO(3-x)N(x) are in the range of 100-150 nm, which are much smaller than NaTaO(3) particles synthesized by traditional solid state reaction method. The photocatalytic activities of NaTaO(3-x)N(x) were examined by methylene blue (MB) aqueous solution under UV light. It is found that the photocatalytic activity of NaTaO(3-x)N(x) depend strongly on the doping content of N, and sample NaTaO(2.961)N(0.039) shows the highest photocatalytic activity for the degradation of MB. Furthermore, it is also found that NaTaO(3-x)N(x) catalysts display super structural stabilities during photocatalytic degradation, and could recover their photocatalytic activity after calcination at 500 degrees C, suggesting a promising utilization of such photocatalyst.

Controlled formation of a flower-like CdWO4–BiOCl–Bi2WO6 ternary hybrid photocatalyst with enhanced photocatalytic activity through one-pot hydrothermal reaction

In this study, we synthesized a flower-like CdWO4–BiOCl–Bi2WO6 ternary hybrid (CBB) and CdWO4–Bi2WO6 binary composite in the same system using the same raw materials with different molar ratios and compared their photocatalytic activities. The X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM) results verify that the transformation of the CdWO4–BiOCl–Bi2WO6 ternary hybrid to the CdWO4–Bi2WO6 binary composite is a topological transformation. Their photocatalytic performances are evaluated by monitoring the degradation of Rhodamine B (RhB). The ternary hybrid (CBB-0.05) shows enhanced photocatalytic activity as compared to pure CdWO4, BiOCl, Bi2WO6, BiOCl–Bi2WO6, CdWO4–Bi2WO6 (CBB-0.10) and the other CBB composites. This remarkable enhancement is attributed to the fact that the suitable conduction band (CB) positions in the ternary hybrid can form a cascade structure and the two layered compounds BiOCl and Bi2WO6 can epitaxially grow from one phase to another with little strain at the interface; this increases the separation efficiency of charge carriers. In addition, the mechanism of the high photocatalytic activity is discussed based on the photoluminescence (PL) spectra and photoelectrochemical and active species trapping measurements.