Ball milling has been proven to be an efficient method for exfoliating and reassembling heterogeneous layered nanocomposites on a large scale. This study explores the use of ammonium tetrathiomolybdate (NH 4 ) 2 MoS 4 , an ion crystal with an octahedral structure, as both a precursor of layered molybdenum disulfide (MoS 2 ) and an intermediate during ball milling to assist in the exfoliation and fragilization of expandable graphite (EG). Due to its ion crystal structure and high hardness, (NH 4 ) 2 MoS 4 can efficiently transfer and magnify the impacting and shearing forces generated during the ball milling process, accelerating the exfoliation and fragmentation efficiency of EG. Moreover, (NH 4 ) 2 MoS 4 is nano-crystallized by the ball milling forces and uniformly distributed on the carbon nanosheets. Electrochemical performance tests indicate that the resulting nanocomposites, with a satisfactory heterogeneous structure, exhibit excellent Li-storage capacity, achieving 529 mA h g −1 after 150 cycles at a high current density of 500 mA g −1 . The relationship between the microstructure and improved electrochemical performance, as well as the formation mechanism of the product, is discussed in detail. This study provides a new approach for conveniently constructing nanocomposites using two types of layered materials that offer satisfactory rate capability and cyclability, making them potentially suitable for application in Li-ion batteries.
Yujian Rao,Zhenliang Li,Tuo Zhang,Zhehan Wang,Weisheng Li,Xinran Wang,Litao Sun,Yuan Ren,Li Tao
Endowing transition metal dichalcogenides (TMDs) with mesoporous structure can greatly enhance their porosity, accessible specific surface area, and exposed active sites, leading to better performances in applications based on interfacial reactions. Current methods including hard-template (nanocasting) method or thermal-assisted conversion (TAC) still suffer from drawbacks such as cumbersome and environmentally unfriendly process, humidity sensitivity, or ill-defined mesostructures. Herein, the study reports a facile synthesis of ordered mesoporous TMDs/carbon composites by direct organic–inorganic co-assembly in dual solvent (DMF/H 2 O). The amphiphilic block copolymer polyethylene oxide- b -polystyrene (PEO- b -PS) is used as the organic template, and (NH 4 ) 2 MoS 4 or (NH 4 ) 2 WS 4 as the inorganic precursor. After solvent evaporation-induced aggregation assembly and thermal treatments, it results in highly ordered mesoporous MoS 2 , WS 2 , and MoS 2 /WS 2 with highly crystalline framework, high specific surface area (44-91 m 2 g −1 ) and large pore sizes (15–21 nm). Semiconductor gas sensors based on mesoporous TMDs exhibit extraordinary sensing performances toward NO 2 at room temperature, including high sensitivity and ultrahigh selectivity, benefiting from its abundant adsorption sites for gas molecules, fast diffusion rate in well-connected mesopores, and rich edge active sites. This work paves a facile way to develop novel ordered mesoporous TMDs-based semiconductor materials for various applications.
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