Density Gradient Strategy for Preparation of Broken In₂O₃ Microtubes with Remarkably Selective Detection of Triethylamine Vapor

Tubule-like structured metal oxides, combined with macroscale pores onto their surfaces, can fast facilitate gas-accessible diffusion into the sensing channels, thus leading a promoted utilization ratio of sensing layers. However, it generally remains a challenge for developing a reliable approach to prepare them. Herein, this contribution describes a density gradient strategy for obtaining broken In₂O₃ microtubes from the In₂O₃ products prepared using a chemical conversion method. These In₂O₃ microtubes hold a diameter about 1.5 μm with many broken regions and massive ultrafine nanopores onto their surfaces. When employed as a sensing element for detection of triethylamine (TEA) vapor, these broken In₂O₃ microtubes exhibited a significant response toward TEA at 1–100 ppm and the lowest detected concentration can reach 0.1 ppm. In addition, an excellent selectivity of the sensor to TEA was also displayed, though upon exposure of other interfering vapors, including ammonia, methanol, ethanol, isopropanol, acetone, toluene, and hydrogen. Such promoted sensing performances toward TEA were ascribed to the broken configuration (superior gas permeability and high utilization ratio), one-dimensional configuration with less agglomerations, and low bond energy for C–N in a TEA molecule

Semimetallic 1T′ WTe₂ Nanorods as Anode Material for the Sodium Ion Battery

Highly crystalline semimetallic 1T′ WTe₂ nanorods (WTe₂ NRs) and WTe₂ nanoflowers (WTe₂ NFs) are applied as anode materials for the sodium ion battery (SIB) for the first time. WTe₂ NRs and NFs are synthesized through a novel two-step process with hydrothermal-derived WO₃ transformed into WTe₂ NRs and NFs after a chemical vapor deposition process. The performance of the WTe₂ SIB anode is highly influenced by WTe₂ morphology. WTe₂ NRs have shown high capacity in sodium ion storage, with an excellent rate and cycling stability. The initial discharge capacity for WTe₂ NRs is 442 mA h g^–1 at the current density of 0.1 A g^–1 and remains at 221 mA h g^–1 after 100 cycles, while WTe₂ NFs show 324 mA h g^–1 initial capacity and remain at 260 mA h g^–1 after 40 cycles. The Coulombic efficiencies of both WTe₂ NR and NF anodes are as high as 98.83 and 97.96% from the second cycle, respectively

Electroassisted Fabrication of Free-Standing Silica Structures of Micrometer Size

Free-standing porous silica microstructures have been made via the electroassisted deposition of silica in an appropriately patterned array of recessed electrodes consisting of hydrophilic and hydrophobic domains. The 100 nm deep recessed indium tin oxide (ITO) electrodes were prepared by a photolithographic/chemical etching process on Glass/ITO/Au substrates. Hydrophobic areas were formed by passivation of unetched gold with a self-assembled monolayer of 1-octadecanethiol. Application of sufficiently negative potentials produced thick layers of silica that extended across the whole substrate; however, because of adhesion differences of silica on hydrophilic (ITO) and hydrophobic (thiol-modified gold) surfaces, selective removal of silica from the more hydrophobic areas of the substrate was achieved. The surface morphology, porosity, and thickness of resultant microstructures depended on the concentration of tetramethoxysilane in the sol, the electrolysis time, and the applied potential, all of which have been varied. Free-standing silica features of different geometries including bands, squares, and circles, ranging in width from 60 to 500 μm and heights >1 μm, have been prepared using this approach. Scanning electron microscopy (SEM) images showed the materials to consist of aggregates of colloidal particles that extend tens to thousands of nanometers above the surface. Such film-like materials have important characteristics that make them ideally suited as a platform for chemical sensors; most notably, an open framework and the presence of interconnected pores within individual microstructures

Nitrogen and Sulfur Co-Doped Hierarchically Porous Carbon Nanotubes for Fast Potassium Ion Storage

Exploration of advanced carbon anode material is the key to circumventing the sluggish kinetics and poor rate capability for potassium ion storage. Herein, a synergistic synthetic strategy of engineering both surface and structure is adopted to design N, S co-doped carbon nanotubes (NS-CNTs). The as-designed NS-CNTs exhibit unique features of defective carbon surface, hollow tubular channel, and enlarged interlayer space. These features significantly contribute to a large potassium storage capacity of 307 mA h g−1 at 1 A g−1 and a remarkable rate performance with a capacity of 151 mA h g−1 even at 5 A g−1. Furthermore, an excellent cyclability with 98% capacity retention after 500 cycles at 2 A g−1 is also achieved. Systematic analysis by in situ Raman spectroscopy and ex situ TEM demonstrates the structural stability and reversibility in the charge–discharge process. Although the kinetics studies reveal the capacitive-dominated process for potassium storage, density functional theory calculations provide evidence that N, S co-doping contributes to expanding the interlayer space to promote the K-ion insertion, improving the electronic conductivity, and providing ample defective sites to favor the K-ion adsorption.</p

Enhancing Sodium-Ion Storage Behaviors in TiNb₂O₇ by Mechanical Ball Milling

Sodium-ion batteries (SIBs) have shown extensive prospects as alternative rechargeable batteries in large-scale energy storage systems, because of the abundance and low cost of sodium. The development of high-performance cathode and anode materials is a big challenge for SIBs. As is well known, TiNb₂O₇ (TNO) exhibits a high capacity of ∼250 mAh g^–1 with excellent capacity retention as a Li-insertion anode for lithium-ion batteries, but it has rarely been discussed as an anode for SIBs. Here, we demonstrate ball-milled TiNb₂O₇ (BM-TNO) as an SIB anode, which provides an average voltage of ∼0.6 V and a reversible capacity of ∼180 mAh g^–1 at a current density of 15 mA g^–1, and presents excellent cyclability with 95% capacity retention after 500 cycles at 500 mA g^–1. A possible Na storage mechanism in BM-TNO is also proposed