Various photocatalysts have been produced for the oxidation of airborne styrene. Commercial Degussa P25 (supported on vanadia-doped/undoped silica gel) and synthesized titania-pillared clay was used. Selected catalysts were characterized using SEM, TEM, XRD, TGA, UV-vis spectrophotometry, and nitrogen adsorption. This work represents the first phase of a study, aimed at degrading styrene in a fluidized-bed photoreactor, of which will be reported separately.
Hydrogen incorporation into well-defined nanocrystals of anatase titanium dioxide (TiO2) has been investigated by a combination of experimental studies and density functional theory (DFT) calculations. The hydrogenation of TiO2 nanocrystals was determined at 450 °C with an initial hydrogen pressure of 7.0 MP, and storage capacities of 1.0 wt % and 1.4 wt % were achieved for nanocrystals with predominant (001) and (101) surface terminations, respectively. X-ray diffraction and Raman spectroscopy measurements indicate that the TiO2 crystal structure is very well preserved during the hydrogenation. DFT calculations show that hydrogen occupies the interstitial sites between titanium–oxygen octahedra and the energy barrier for hydrogen incorporation through the anatase (101) surface is lower than that through (001).
Solar light induced water splitting on photocatalysts is a very important area of research. Anion doping of photocatalysts normally active only under ultraviolet (UV) light has been reported to be a possible way of increasing visible light photocatalytic performance. Here we report a (111) layered perovskite material Ba5Ta4O15 that was doped with nitrogen. The resulting Ba5Ta4O15–xNx compound exhibited an extraordinary increase in visible light absorbance. The uniform distribution of the nitrogen dopant was attributed to the unique layered (111) structure, which provides intergallery spacings between the perovskite layers for the dopant to diffuse easily in the compound particles during the doping process. It was further verified by density of states that the N 2p states mixed with pre-existing O 2p states that moved the valence band maximum upward without effecting the conduction band, which was composed of the Ta 4d orbital. The doped photocatalysts exhibited not only increased visible light absorbance but increased photocatalytic hydrogen production of ∼50% under simulated solar irradiation, in comparison to that of undoped parent compound.
In the presence of nonionic block-copolymer surfactant, nanocrystalline zirconia particles with MSU mesostructure were synthesized by a novel solid-state reaction route. The zirconia particles possess a nanocrystalline pore wall, which renders higher thermal stability compared to an amorphous framework. To further enhance its stability, laponite, a synthetic clay, was introduced. Laponite acts as an inhibitor to crystal growth and also as a hard template for the mesostructure. High surface area and ordered pore structure were observed in the stabilized zirconia. The results show that the formation of the MSU structure is attributed to reverse hexagonal micelles, which are the products of the cooperative self-assembly of organic and inorganic species in the solid-state synthesis system with crystalline water and hygroscopic water present.
Coupled ZnO/CdS heterostructures based on the Z-scheme mechanism are demonstrated to be highly active photocatalysts for H2 evolution under simulated solar light irradiation due to the greatly prolonged lifetime of photoexcited carriers.
A series of Ti-Zr-O nanotube arrays on Ti-Zr alloys with different ratios of Ti to Zr were prepared by a simple anodization process, and their morphologies, crystal structures and optical properties were investigated. It is found that the morphology, length, crystal structure and optical properties of Ti-Zr-O tubes can be well controlled by adjusting the ratio of Ti to Zr in Ti-Zr alloys. The tubes obtained evolved from circa (ca.) 100 nm to 50 nm in diameter, from ca. 2 to 10 microm in length with increasing Zr content in Ti-Zr alloys. As-prepared tubes grown on the alloys with a Zr content of <70 mol% are amorphous, while cubic phase of ZrO2 is predominately formed in the 90 mol% Zr-Ti alloy. The absorption edge of such tubes was found to span from 250 to 370 nm, and their emission band from 400 nm to 750 nm in photoluminescence spectra decays with the decrease of Zr content. In addition, upon calcination of varied Zr content Ti-Zr-O nanotubes, Zr doped anatase TiO2, zirconium titanate and Ti doped ZrO2 in were obtained.
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