Bulk Fabrication of WS₂ Nanoplates: Investigation on the Morphology Evolution and Electrochemical Performance

Two-dimensional layered chalcogenide WS₂, similar to graphene, is considered to be very interesting for materials scientists. However, to make it a useful material platform, it is necessary to develop sophisticated synthesis methods to control its morphology. In this paper, we present a simple approach to prepare various morphologies of WS₂ nanostructures by direct thermal evaporation of WO₃ and S powders onto Si substrates sputtered with W film without using any nanostructured W-contained precursors and highly toxic sulfide gases. This method can produce bulk quantities of pure hexagonal, horizontally grown WS₂ nanoplates, vertically grown nanoplates, and nanoplate-formed flowers simply by tuning the distance between the substrate and source powders. The synthesis mechanism and morphology evolution model were proposed. Moreover, when employed as a thin-film anode material, the Li-ion battery with as-prepared, vertically grown WS₂ nanoplates presented a rechargeable performance between 3 and 0.01 V with a discharge capacity of about 773 mAh/cm³ after recycling three times, much better than its already-reported counterparts with randomly distributed WS₂ nanosheet electrodes, but the battery with horizontally grown WS₂ nanoplates could not show any charge–discharge cycling property, which could be attributed to the different structures of WS₂ anodes for Li⁺ ion intercalation or deintercalation

Internal and External Cultivation Strategy toward Efficient Electrochemical Oxygen Evolution in Cobalt Pentlandite

Oxygen evolution reaction (OER) plays an important role in various renewable energy conversion scenarios for carbon neutralization. Constructing interface engineering and element doping has been extensively developed to tune the electrocatalytic OER activity of electrocatalysts. However, it is challenging to simultaneously conduct doping and interface engineering, and insights into the structure–property relationship are insufficient. Here, we designed the cobalt pentlandite OER catalyst (V-CNFS/Ni9S8) by an external and internal cultivation strategy that combines the external modulation of active sites of the catalyst surface through heterostructure construction and the internal modulation of the electronic structure of cobalt pentlandite through heteroatom doping. At the same time, this strategy also leads to the redistribution of interfacial electrons, thereby enhancing the catalytic activity. The elaborate electrocatalyst V-CNFS/Ni9S8 with optimized composition and typical hollow structure accelerates the electrochemical reactions, which can show an overpotential of 305 mV at 50 mA cm–2, and high stability for 72 h. This work reports an efficient OER electrocatalyst, which may open numerous opportunities to the development of cobalt pentlandite catalysts in renewable energy conversion and storage technology

Interpenetrating Network-Structured Al₂O₃–Y₃Al₅O₁₂ Eutectic Composite Grown by Containerlessly Directional Solidification Process

Directionally solidified (DS) Al₂O₃/YAG eutectic composites with microstructures of three-dimensionally continuous networks were prepared using containerlessly directional solidification through an aerodynamic levitator. The morphological evolution of DS eutectics was studied at a large growth rate range. The DS eutectics present irregular “Chinese script” morphologies at growth rates of 9 μm/s, transforming into complex regular eutectic morphologies with growth rates increasing to 68 μm/s. At a superhigh crystal growth rate of 800 μm/s, the DS eutectics showed regular lamellar morphologies. The indentation hardness and Young’s modulus of DS Al₂O₃/YAG eutectic composites at growth rates of 68 μm/s are 22.3 and 338 GPa, respectively