IF-WS2 and NT-WS2 of WS2 Nanomaterials and Preparation

Various forms of WS₂ nanomaterials include nanosheets, IF-WS₂, NT-WS₂, and other forms. Chemical gas-solid reactions are the most well-known and established method for the synthesis of IF WS₂ nanoparticles and nanotubes. Tenne et al. initially synthesized IF WS₂ nanoparticles and nanotubes using WO₃ films and H₂S in a reducing atmosphere (95% N₂ + 5% H₂) at 850 °C. However, only a small amount of products could be synthesized by this method.

Feldman et al. replaced the WO₃ films with commercial WO₃ powder and made some improvements to the reactor, synthesizing considerable quantities (50 mg at a time). in 2000, they designed a fluidized bed reactor with the same reaction material to achieve continuous preparation of IF WS₂ nanoparticles and nanotubes.

In order to control the structure of IF WS₂ nanoparticles and nanotubes by changing the process parameters during the synthesis, Margolin et al. synthesized IF-WS₂ nanoparticles and NT-WS₂ by gas-solid reaction and then investigated their growth mechanisms.

H₂S is known to be highly toxic, corrosive, flammable, and explosive, so Wiesel et al. synthesized IF-WS₂ using nanopowder of the corresponding metal oxides, sulfur as a solid precursor, and NaBH₄ or LiAlH₄ as a hydrogen-releasing agent. The products were obtained by conventional furnace heating to about 900 °C or by photothermal ablation of high-concentration white light at higher temperatures.

In addition, other methods have been used to prepare IF-WS₂ or NT-WS₂, such as thermal decomposition, templating, and chemical vapor phase transport. In addition to the above three (nanosheet, IF WS₂, and NT WS₂) morphologies, WS₂ nanomaterials also have other morphological types such as nanospheres, nanowires, nanorods, and nanoflowers.

These special morphologies of WS₂ also have potential applications due to their porous structure and increased specific surface area. By adjusting the reaction conditions, WS₂ with different morphologies is usually considered to be prepared by the solvothermal method.

Researchers prepared low-dimensional WS₂ (nanospheres, nanowires, and nanorods) using cetyltrimethylammonium bromide (CTAB) as a surfactant. The results showed that the concentration of CTAB has a great influence on the morphology of WS₂. Many ordered microstructures show a nanometer range due to the phenomenon that the active agent molecules can aggregate in solution to form micelles, microemulsions, liquid crystals, and vesicles.

These ordered microstructures can provide a special microenvironment for chemical reactions. They can be used as microreactors or templates for the synthesis of various nanomaterials. Depending on the concentration of the aqueous solution, the surfactants exhibit different aggregated forms, leading to the subsequent formation of WS₂ with different morphologies. In addition, three-dimensional nanoflower-like WS₂ can also be synthesized by the solvothermal method.

Article Source: Sun, CB., Zhong, YW., Fu, WJ. et al. Tungsten disulfide nanomaterials for energy conversion and storage. Tungsten 2, 109–133 (2020).

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