Semiconductors showing high efficient photocatalytic activity have attracted great interest, because they provide a potential solution to many environmental pollution problems that humankind is currently facing. This work reports on the sol-gel synthesis of Na2Ta4O11 nanocrystals and its photocatalytic performance toward Red G. The samples were carefully characterized by X-ray diffraction, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, and the Barrett–Emmett–Teller technique. By modulating the synthetic condition, the sol-gel reaction yielded pure Na2Ta4O11 nanocrystals with diameter of ~32 nm from the peak broadening of (006) plane using Scherrer formula. It is found that the as-prepared Na2Ta4O11 nanocrystals showed a band gap energy of 3.63 eV, which is much smaller than that of Na2Ta4O11 prepared by flux approach. The relative narrowed band gap energy of Na2Ta4O11 nanocrystals may predict superior photocatalytic activity. By careful photocatalytic test, it is found that Na2Ta4O11 nanocrystals showed excellent photocatalytic activity toward Red G. The photocatalytic degradation efficiency was estimated to be 94.0% within a time intervals of 40 minutes. Controlled experiment by adding active species scavengers gave evidence that the degradation of Red G is dominated by the oxidation reaction of the generated O2-∙ active species taking place on the surface of the photocatalyst.
TiO2/SBA-15 and AgCl loaded on TiO2/SBA-15(AgCl-TiO2/SBA-15) composites were synthesized by a facile method. All products were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and N2adsorption-desorption analysis. Photocatalytic activities of the composites were assessed by the photocatalytic decomposition of methyl orange (MO). The results indicated that TiO2or TiO2-AgCl existed in the matrix SBA-15, which reduced the specific surface area, pore volume and pore size of the matrix. The photocatalytic performances of TiO2/SBA-15 were higher than that of pure TiO2, and the resultant AgCl-TiO2/SBA-15 composites showed much higher photocatalytic performances than TiO2/SBA-15.
The energy bands of La -doped ZnO were studied systematically by the density functional theory (DFT). Based on the data of the band structure, DOS (Density of State) and PDOS( Partial Density of States), atomic populations and net charge, the influence on the energy band structure of the macrostructure of ZnO and La-doped ZnO was investigated. The results showed that the free electrons were produced by the doping of La on (or in) ZnO crystal. The Fermi energy was shifted up to the conduction band, making the ZnO particles having the characters of degenerated semiconductor. The excitation from impurity states to the conduction band may account for the blue shift of the absorption edge in the model of La-doped ZnO. Comparison with the different models of the La doped/loaded on the ZnO surface, La atoms loaded on the surface of ZnO and La atoms replaced of Zn atoms on the ZnO surface, the shift to the lower energy location were found after La doping/loading. The more shift and the large band gap was found for the model of La doped on the Zn position in the ZnO crystal.
In this paper, a density functional theory based on the first-principles was employed to evaluate the adsorption of CH4onto the surfaces of BaZrO3catalysts. The absorption mechanism was derived by population and electronic states analysis on the basis of the electronic and surface structure calculations for BaZrO3. The (001) surface was calculated to be the adsorption surface for CH4owing to its high stability. Comparing to that for CH4absorbed on (001) surfaces, the frontier energy state was found to the key factor in controlling the adsorption behavior, which is mainly contributed by oxygen and Zr ions of the B-site. The most favorite adsorption site for CH4was located at B-sites of BaZrO3, where the A-site ions would adjust the charge of B-site ions and moreover affect the CH4adsorption. The results reported in this work may provide the fundamental understanding about the absorption of CH4inflammation catalysts with high-activity and high-stability.
CaMoO4 microcrystals with controllable morphologies and luminescent properties were successfully synthesized via hydrothermal treatment. The as-prepared samples are characterized using X-ray powder diffraction, scanning electron microscopy; Fourier transformed infrared spectra. By adjusting the fundamental experimental parameters including reaction time, temperature and the amount of organic additives, CaMoO4 exhibited various morphologies, such as particles, dumbbells as well as flowers. Moreover, it is seen that CaMoO4 can be well crystallized with tetragonal structure at room temperature. The photoluminescence spectra of CaMoO4 display a strong and broad band emission with a maximum at 550 nm under excitation wavelength of 310 nm at room temperature. The luminescent intensity of CaMoO4 varied with the reaction time and temperature and was optimized at 200 oC, 45 h. The work provides a facile synthetic route for the construction of inorganic materials with controllable morphologies and luminescent properties
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