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Preparation, Characterization and Formation Mechanism of Single Crystal Tungsten Oxide Nanosheets Based on Intercalation Chemistry

wallpapers News 2021-11-25
Preparation, Characterization and Formation Mechanism of Single Crystal Tungsten Oxide Nanosheets Based on Intercalation Chemistry
Combining the advantages of intercalation chemistry and wet chemical methods, a new method for preparing two-dimensional tungsten oxide (WO3) nanosheet single crystals with high specific surface area, large diameter-to-thickness ratio, and easy dispersion was established. The micron-sized WO3 and Bi2O3 are solid-phase reacted to form the layered compound Bi2W2O9 at 800°C; the obtained Bi2W2O9 is selectively dissolved out of the [Bi2O2] layer by hydrochloric acid to obtain the protonated H2W2O7·xH2O phase. Using H2W2O7·xH2O as the tungsten source and the inorganic-organic hybrid nanobelt obtained by intercalation of octylamine as the precursor, the orthogonal phase WO3·H2O nanosheets are obtained after the organic components in the precursor are removed by nitric acid oxidation; WO3·H2O nanosheets are heat-treated at 250-450°C and air atmosphere for 2-5h (heating rate is 2°C/min) to obtain monoclinic phase WO3 single crystal nanosheets. TEM and SEM analysis results show that the morphology of single crystal WO3·H2O and WO3 nanosheets are similar, with a size of (200~500)nm×(200~500)nm and a thickness of 10~30nm; the obtained WO3·H2O and WO3 The thickness directions of the nanosheet single crystal are [010] and [001], respectively. The N2 adsorption results show that the specific surface area of WO3·H2O and WO3 nanosheets can reach 250 and 180 m^2/g, respectively.
Semiconductor multi-level composite materials have steric hindrance and large surface area, which can provide a large number of reactive sites for photocatalytic reactions. In addition, due to the different energy levels of conduction band and valence band between different semiconductors, photogenerated carriers can be transferred from higher energy levels to lower energy levels, thereby effectively separating electrons and holes. Semiconductor multi-level composite materials have become a research hotspot of nano-photocatalytic materials today. In this paper, two-dimensional W03 nanosheets are used as the substrate, and TiO2, CdS, Ag/AgCl nanocrystals are grown on W03 nanosheets to construct a WO3 nanosheet-based semiconductor multi-level composite photocatalyst, and its photocatalytic performance is studied. Using commercially available tungstic acid (H2WO4) as a tungsten source, a tungsten-based inorganic-organic hybrid nanobelt was prepared by intercalation reaction; the organic matter was selectively oxidized by concentrated nitric acid solution, and the resulting product was finally calcined to obtain a single crystal WO3 nanobelt. piece. The size of the obtained two-dimensional WO3 nanosheet is (100-250)×(250-350)nm, and the thickness is about 10-30nm. It can form a "House of Cards" structure when stacked in space, and the structure is fluffy and basically without agglomeration. , Large surface area, steric hindrance effect, can provide a large number of reactive sites for photocatalytic reaction, is a good matrix for the construction of semiconductor multi-level composite photocatalyst. Using butyl titanate as the titanium source, WO3 nanosheets doped TiO2 fibers were prepared by electrospinning. The diameter of the obtained TiO2 fibers was 1~2μm, and the WO3 nanosheets were evenly wrapped in the TiO2 fibers. With the increase of the doping amount of W03 nanosheets, the crystal form of TiO2 fibers gradually changed from rutile type to anatase type, and at the same time it became easier to break, and the adsorption performance of the prepared WO3 nanosheets doped TiO2 fibers increased. 
 

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